1. |
S. Isayama, S. Shinohara, T. Hada, S. H. Chen, Spatio-temporal behavior of density jumps and the effect of neutral depletion in high-density helicon plasma, *Physics of Plasmas*, 10.1063/1.5093920, 26, 5, id.053504(1)-id.053504(10), 2019.05, Abrupt jumps in the density of helicon discharge have been observed following continuous variation of parameters such as the external magnetic field and the radio frequency (RF) input power. In this study, we show the spatio-temporal behavior of such density jumps and the mode transition in a helicon plasma. It is found that the density jump process is characterized by two temporal phases with the contribution of higher axial modes, changing the antenna current (and thus the RF power). We also investigated the effect of the neutral depletion on the local plasma equilibrium. The temporal fluctuation of the plasma density caused by the neutral depletion was observed.. |

2. |
S. Isayama, S. Shinohara, T. Hada, S. H. Chen, Underlying competition mechanisms in the dynamic profile formation of high-density helicon plasma, *Physics of Plasmas*, 10.1063/1.5063506, 26, 2, id.023517(1)-id.023517(9), 2019.02. |

3. |
Yasuhito Narita, Tohru Hada, Origin of nonlinear density fluctuations in the foreshock region, *Earth, Planets and Space*, 10.1186/s40623-018-0943-0, 70, 1, id.171(1)-id.171(7), 2018.10, The foreshock plasma exhibits large-amplitude disturbance in the plasma density and the magnetic field. The question of the density response to the magnetic field fluctuation is addressed and studied observationally and statistically using the in situ Cluster spacecraft data of the foreshock plasma. Three major findings are obtained. First, the density response is unique to the magnetic field fluctuation and is of the fast magnetosonic mode type. Second, the density response to the total magnetic energy density (simply subtracting by the mean field) exhibits a clear scaling to the beta-tilde parameter defined as the squared ratio of the sound speed to the Alfvén speed. We interpret that the total fluctuations mostly represent linear-mode waves, and the scaling law has a potential application to estimate the plasma parameter beta using the fluctuation data of the density and the magnetic field only. Third, the density response to the nonlinear (or large-amplitude) magnetic field fluctuation has a weak agreement with the theoretical expectation from the quasi-static balance with a larger degree of scattering in the data. We conclude that the foreshock plasma overall exhibits the linear-mode waves (fast mode) and a moderate degree of nonlinear fluctuations. The concept of the quasi-static balance is partly justified and applicable in the foreshock plasma.. |

4. |
Shogo Isayama, Shunjiro Shinohara, Tohru Hada, Review of Helicon High-Density Plasma: Production Mechanism and Plasma/Wave Characteristics, *Plasma and Fusion Research*, 10.1585/pfr13.1101014, 13, 1101014(1)-1101014(25), 2018.03. |

5. |
Masaru Nakanotani, Tohru Hada, Shuichi Matsukiyo, Diffusive shock acceleration of cosmic rays from two stationary shocks, *Earth, Planets and Space*, 10.1186/s40623-018-0799-3, 70, 1, 2018.12, Diffusive shock acceleration (Fermi acceleration) of cosmic rays in a system containing two shock waves is investigated using test particle simulations and analysis of the diffusion convection equation. We assume that the cosmic ray acceleration timescale is much less than the approaching timescale of the two shocks. Low-energy cosmic rays are primarily accelerated as they interact with one of the two shocks. However, as they are energized, and their mean free path becomes comparable to the separation distance of the two shocks, they start to accelerate as they interact with both shocks. As a result, a double power-law-type spectrum for the cosmic ray distribution is produced. The numerical result is well explained by a model based on the diffusion convection equation, which accounts for the dependence of the diffusion coefficient on the cosmic ray energy. The break point of the spectrum can be estimated by considering transport of cosmic rays from one shock to the other.[Figure not available: see fulltext.].. |

6. |
Fumiko Otsuka, Shuichi Matsukiyo, Arpad Kis, Kento Nakanishi, Tohru Hada, Effect of Upstream ULF Waves on the Energetic Ion Diffusion at the Earth's Foreshock. I. Theory and Simulation, *Astrophysical Journal*, 10.3847/1538-4357/aaa23f, 853, 2, 2018.02, Field-aligned diffusion of energetic ions in the Earth's foreshock is investigated by using the quasi-linear theory (QLT) and test particle simulation. Non-propagating MHD turbulence in the solar wind rest frame is assumed to be purely transverse with respect to the background field. We use a turbulence model based on a multi-power-law spectrum including an intense peak that corresponds to upstream ULF waves resonantly generated by the field-aligned beam (FAB). The presence of the ULF peak produces a concave shape of the diffusion coefficient when it is plotted versus the ion energy. The QLT including the effect of the ULF wave explains the simulation result well, when the energy density of the turbulent magnetic field is 1% of that of the background magnetic field and the power-law index of the wave spectrum is less than 2. The numerically obtained e-folding distances from 10 to 32 keV ions match with the observational values in the event discussed in the companion paper, which contains an intense ULF peak in the spectra generated by the FAB. Evolution of the power spectrum of the ULF waves when approaching the shock significantly affects the energy dependence of the e-folding distance.. |

7. |
Masaru Nakanotani, Shuichi Matsukiyo, Tohru Hada, Christian X. Mazelle, Electromagnetic Structure and Electron Acceleration in Shock-Shock Interaction, *Astrophysical Journal*, 10.3847/1538-4357/aa8363, 846, 2, 2017.09, A shock-shock interaction is investigated by using a one-dimensional full particle-in-cell simulation. The simulation reproduces the collision of two symmetrical high Mach number quasi-perpendicular shocks. The basic structure of the shocks and ion dynamics is similar to that obtained by previous hybrid simulations. The new aspects obtained here are as follows. Electrons are already strongly accelerated before the two shocks collide through multiple reflection. The reflected electrons self-generate waves upstream between the two shocks before they collide. The waves far upstream are generated through the right-hand resonant instability with the anomalous Doppler effect. The waves generated near the shock are due to firehose instability and have much larger amplitudes than those due to the resonant instability. The high-energy electrons are efficiently scattered by the waves so that some of them gain large pitch angles. Those electrons can be easily reflected at the shock of the other side. The accelerated electrons form a power-law energy spectrum. Due to the accelerated electrons, the pressure of upstream electrons increases with time. This appears to cause the deceleration of the approaching shock speed. The accelerated electrons having sufficiently large Larmor radii are further accelerated through the similar mechanism working for ions when the two shocks are colliding.. |

8. |
Yasuhito Narita, Yoshihiro Nishimura, Tohru Hada, Minimum variance projection for direct measurements of power-law spectra in the wavenumber domain, *Annales Geophysicae*, 10.5194/angeo-35-639-2017, 35, 3, 639-644, 2017.05, Minimum variance projection is widely used in geophysical and space plasma measurements to identify the wave propagation direction and the wavenumber of the wave fields. The advantage of the minimum variance projection is its ability to estimate the energy spectra directly in the wavenumber domain using only a limited number of spatial samplings. While the minimum variance projection is constructed for discrete signals in the data, we find that the minimum variance projection can reasonably reproduce the spectral slope of the power-law spectrum if the data represent continuous power-law signals. The spectral slope study using the minimum variance projection is tested against synthetic random data with a power-law spectrum. The method is applicable even for a small number of spatial samplings. Conversely, the spatial aliasing causes a flattening of the spectrum.. |

9. |
Yasuhiro Nariyuki, Makoto Sasaki, Naohiro Kasuya, Tohru Hada, Masatoshi Yagi, Phase coherence among the Fourier modes and non-Gaussian characteristics in the Alfven chaos system, *Progress of Theoretical and Experimental Physics*, 10.1093/ptep/ptx016, 2017, 3, 2017.03, Non-Gaussian characteristics in time series of the Alfven chaos system are discussed. The phase coherence index, a measure defined by using the surrogate data method and the structure function, is used to evaluate the phase coherence among the Fourier modes. Through Monte Carlo significance testing, it is found that the phase coherence decays monotonically with increasing dissipative parameter and time scale. By applying the Mori projection operator method assuming the Markov process, a model equation for the time correlation function is derived from the generalized Langevin equation. As opposed to the result of the phase coherence analysis, it is concluded that the difference between the direct numerical simulation and the model equation becomes pronounced as the dissipative parameters are increased. This suggests that, even when the phase coherence index is not significant, the underlying physical system may be a non-Gaussian process.. |

10. |
S. Isayama, T. Hada, S. Shinohara, T. Tanikawa, Is the bulk mode conversion important in high density helicon plasma?, *Physics of Plasmas*, 10.1063/1.4951017, 23, 6, 2016.06. |

11. |
Y. Nariyuki, T. Umeda, T. Suzuki, T. Hada, Note on one-fluid modeling of low-frequency Alfvénic fluctuations in a solar wind plasma with multi-ion components, *Physics of Plasmas*, 10.1063/1.4936798, 22, 12, 2015.12. |

12. |
S. Isayama, T. Hada, S. Shinohara, T. Tanikawa, Self-Consistent Discharge Growing Model of Helicon Plasma, *DPP15, Am. Phys. Soc.*, DPP15, 2015.11. |

13. |
F. Otsuka, T. Hada, S. Shinohara, T. Tanikawa, Penetration of a radio frequency electromagnetic field into a magnetized plasma: one-dimensional PIC simulation studies, *Earth, Planets and Space*, 10.1186/s40623-015-0244-9, 67, 85, 2015.06. |

14. |
K. Wang, C-H Lin, L-Y Wang, T. Hada, T. Y. Nishimura, D. Turner, V. Angelopoulos, Pitch-angle distributions of electrons at dipolarization sites during geomagnetic activity: THEMIS observations, *J. Geophys. Res.*, 10.1002/2014JA020176, 119, 12, 2014.11. |

15. |
M. G. Cardinal, A. Yoshikawa, H. Liu, M. Watanabe, S. Abe, T. Uozumi, G. Maeda, T. Hada, K. Yumoto, Collisionless damping of circularly polarized nonlinear Alfven waves in solar wind plasmas with and without beam protons , *Space Weather*, 10.1002/2014SW001110, 12, 10, 2014.10. |

16. |
S. Isayama, T. Hada, S. Shinohara, T. Tanikawa, Modeling of Helicon Wave Propagation and the Physical Process of Helicon Plasma Production, *DPP14, Am. Phys. Soc.*, DPP14, 2014.10. |

17. |
Y. Nariyuki, Tohru Hada, K. Tsubouchi, Collisionless damping of circularly polarized nonlinear Alfvén waves in solar wind plasmas with and without beam protons, *Astrophysical Journal*, 10.1088/0004-637X/793/2/138, 793, 2, 2014.10, The damping process of field-aligned, low-frequency right-handed polarized nonlinear Alfvén waves (NAWs) in solar wind plasmas with and without proton beams is studied by using a two-dimensional ion hybrid code. The numerical results show that the obliquely propagating kinetic Alfvén waves (KAWs) excited by beam protons affect the damping of the low-frequency NAW in low beta plasmas, while the nonlinear wave-wave interaction between parallel propagating waves and nonlinear Landau damping due to the envelope modulation are the dominant damping process in high beta plasmas. The nonlinear interaction between the NAWs and KAWs does not cause effective energy transfer to the perpendicular direction. Numerical results suggest that while the collisionless damping due to the compressibility of the envelope-modulated NAW plays an important role in the damping of the field-aligned NAW, the effect of the beam instabilities may not be negligible in low beta solar wind plasmas.. |

18. |
Y. Nariyuki, T. Hada, K. Tsubouchi, Collisionless damping of circularly polarized nonlinear Alfven waves in solar wind plasmas with and without beam protons , *The Astrophysical Journal*, DOI:10.1088/0004-637X/793/2/138, 793, 2, 138, 2014.09. |

19. |
S. Shinohara, H. Nishida, T. Tanikawa, T. Hada, I. Funaki, K. P. Shamrai, Development of Electrodeless Plasma Thrusters With High-Density Helicon Plasma Sources, *IEEE Transactions on Plasma Science*, DOI: 10.1109/TPS.2014.2313633, 42, 5, 1245-1254, 2014.05. |

20. |
G. S. Lakhina, B. T. Tsurutani, A. C.L. Chian, Tohru Hada, G. J. Morales, R. H.J. Grimshaw, Introduction to this special issue "Nonlinear waves and chaos in space plasmas", *Nonlinear Processes in Geophysics*, 10.5194/npg-21-583-2014, 21, 3, 583-585, 2014.05. |

21. |
Y. Nariyuki, T. Umeda, T. K. Suzuki, T. Hada, Ion acceleration by parallel propagating nonlinear Alfvén wave packets in a radially expanding plasma, *Nonlinear Processes in Geophysics*, 21, 1, 339-346, 2014.02. |

22. |
V. Munoz, F. A. Asenjo, M. Dominguez, R. A. Lopez, J. A. Valdivia, A. Vinas, T. Hada, Large-amplitude electromagnetic waves in magnetized relativistic plasmas with temperature, *Nonlinear Processes in Geophysics*, 21, 1, 217-236, 2014.02. |

23. |
Y. Nariyuki, T. Umeda, T. K. Suzuki, Tohru Hada, Ion acceleration by parallel propagating nonlinear Alfvén wave packets in a radially expanding plasma, *Nonlinear Processes in Geophysics*, 10.5194/npg-21-339-2014, 21, 1, 339-346, 2014.02, The numerical simulation of the nonlinear evolution of the parallel propagating Alfvén waves in a radially expanding plasma is performed by using a kinetic-fluid model (the Vlasov-MHD model). In our study, both the nonlinear evolution of the Alfvén waves and the radial evolution of the velocity distribution function (VDF) are treated simultaneously. On the other hand, important ion kinetic effects such as ion cyclotron damping and instabilities driven by the non-equilibrium ion velocity distributions are not included in the present model. The results indicate that the steepened Alfvén wave packets outwardly accelerate ions, which can be observed as the beam components in the interplanetary space. The energy of imposed Alfvén waves is converted into the longitudinal fluctuations by the nonlinear steepening and the nonlinear Landau damping. The wave shoaling due to the inhomogeneity of the phase velocity is also observed.. |

24. |
V. Muñoz, F. A. Asenjo, M. Domínguez, R. A. López, J. A. Valdivia, A. Viñas, Tohru Hada, Large-amplitude electromagnetic waves in magnetized relativistic plasmas with temperature, *Nonlinear Processes in Geophysics*, 10.5194/npg-21-217-2014, 21, 1, 217-236, 2014.02. |

25. |
Shunjiro Shinohara, Hiroyuki Nishida, Takao Tanikawa, Tohru Hada, Ikkoh Funaki, Konstantin P. Shamrai, Development of electrodeless plasma thrusters with high-density helicon plasma sources, *IEEE Transactions on Plasma Science*, 10.1109/TPS.2014.2313633, 42, 5, 1245-1254, 2014, Helicon plasma sources are very useful in many aspects and are applicable to many fields across science and technology, as they can supply high-density (~10^{13} cm^{-3}) plasmas with a broad range of external operating parameters. In this paper, developed, featured sources with various sizes are characterized along with discussions on their particle production efficiency. This paper aims to develop systems that can realize schemes with completely electrodeless plasma production and acceleration. This is expected to mitigate the existing problems of the finite lifetimes inherent in electric plasma propulsion tools. Experimental and theoretical approaches that implement such schemes are presented.. |

26. |
S. Isayama, T. Hada, S. Shinohara, T. Tanikawa, Helicon wave propagation in a non-uniform plasma, *Proc. 15th Cross Straits Symp. Ene. Envir. Sci. Tech.*, 275-276, 2013.11. |

27. |
Fumiko Otsuka, Tohru Hada, Shunjiro Shinohara, Takao Tanikawa, Takeshi Matsuoka, Numerical studies of ponderomotive acceleration and ion cyclotron resonance Application to next generation electric thrusters, *Plasma and Fusion Research*, 10.1585/pfr.8.1406012, 8, 2013, 2013.06, We have examined ponderomotive acceleration/ion cyclotron resonance (PA/ICR) of argon ions by performing test particle simulations. The PA gives rise to the pure parallel acceleration of ions, while the ICR causes the perpendicular ion heating followed by the energy conversion from the perpendicular to the parallel direction in the presence of a divergent background magnetic field. The energy gain by the PA/ICR is classified in terms of the adiabatic parameter, δ = L_{B}ω_{0}/v_{0}, where LB is the axial divergent scale length of the background magnetic field, ω0 is the ion gyrofrequency at the resonance, and v0 is the initial ion drift velocity along the axial magnetic field. For δ<100, the energy gain, δ, due to the PA/ICR increases as δ increases. For δ > 100, δ saturates since the increased axial velocity of the ion via the PA reduces the transit time to cross the acceleration region. When the externally applied rf electric field intensity is increased to 1000V/m, we find a maximal 60% increase in the energy gain for the PA/ICR scheme compared with the energy gain by the ICR only. We have applied the PA/ICR scheme to the next-generation electric thruster, and have estimated the thrust including ion wall-loss and ion-neutral collisions.. |

28. |
S. Shinohara, T. Tanikawa, T. Hada, I. Funaki, H. Nishida, T. Matsuoka, F. Otsuka, K. P. Shamrai, T. S. Rudenko, et al, High-Density Helicon Plasma Sources: Basics and Application to Electrodeless Electric Propulsion , *Trans. Fusion Sci. Technol.*, Vol. 63, pp. 164-167 , 2013.03. |

29. |
F. Otsuka, T. Hada, S. Shinohara, T. Tanikawa, T. Matsuoka, Numerical Modeling of Electrodeless Electric Thruster by Ion Cyclotron Resonance/Ponderomotive Acceleration, *Plasma Fusion Research *, Vol. 8, doi:2406067 (7pages) , 2013.03. |

30. |
K. Yamanokuchi, T. Hada, S. Shinohara, Application of the external Rotating Magnetic Field (RMF) to next-generation electric thrusters by numerical analysis, *Proc. 14th Cross Straits Symp. Ene. Envir. Sci. Tech.*, 245-246, 2013.02. |

31. |
S. Isayama, T. Hada, S. Shinohara, T. Tanikawa, Dispersion properties of helicon waves in a non-uniform cylindrical plasma, *Proc. 14th Cross Straits Symp. Ene. Envir. Sci. Tech.*, 160-161, 2013.02. |

32. |
F. Otsuka, T. Hada, S. Shinohara, T. Tanikawa, T. Matsuoka, Numerical Studies of Ponderomotive Acceleration and Ion Cyclotron Resonance: Application to Next Generation Electric Thrusters, *Plasma Fusion Research *, 8, doi:1406012 (14pages) , 2013.01. |

33. |
T. Nakamura, K. Yokoi, H. Nishida, T. Matsuoka, I. Funaki, S. Shinohara, T. Tanikawa, T. Hada, T. Motomura, K. P. Shamrai, T. S. Rudenko, Study on Helicon Plasma Lissajous Acceleration for Electrodeless Electric Propulsion, *Trans. of the Japan Soc. for Aeronautical and Space Sci. Aerospace Technol. Japan*, 10, 17-23, 2012.10. |

34. |
Takeshi Matsuoka, Timofei S. Rudenko, Ikkoh Funaki, Konstantin P. Shamrai, Takahiro Nakamura, Hiroyuki Nishida, Takao Tanikawa, Tohru Hada, Shunjiro Shinohara, One dimensional modeling of radio frequency electric field penetration into magnetized plasmas, *Japanese Journal of Applied Physics, Part 1: Regular Papers & Short Notes*, 10.1143/JJAP.51.096201, 51, 9, 2012.09, Full penetration of RF electric fields into magnetized plasmas is expected in order to realize the Lissajous helicon plasma accelerator (LHPA). We study the electric field penetration in bulk plasma in one-dimensional electrostatic approximation using two analytical models: the matrix sheath model and the vacuum gap model. An identical formula for the electric field is obtained from the models. The formula is benchmarked by particlein-cell (PIC) simulations. The full penetration of the electric field is realized when the relation (q ≪ 0:01) is satisfied, where q is the measure of the degree of the shielding effect due to plasma density and electron magnetization.. |

35. |
Y. Nariyuki, T. Hada, T. Tsubouchi, Nonlinear dissipation of circularly polarized Alfvén waves due to the beam-induced obliquely propagating waves, *Physics of Plasmas*, 082317, 19, 8, 082317-1-082317-8, 2012.08. |

36. |
Y. Nariyuki, Tohru Hada, K. Tsubouchi, Nonlinear dissipation of circularly polarized Alfvén waves due to the beam-induced obliquely propagating waves, *Physics of Plasmas*, 10.1063/1.4748296, 19, 8, 2012.08, In the present study, the dissipation processes of circularly polarized Alfvén waves in solar wind plasmas including beam components are numerically discussed by using a 2-D hybrid simulation code. Numerical results suggest that the parent Alfvén waves are rapidly dissipated due to the presence of the beam-induced obliquely propagating waves, such as kinetic Alfvén waves. The nonlinear wave-wave coupling is directly evaluated by using the induction equation for the parent wave. It is also observed both in the 1-D and 2-D simulations that the presence of large amplitude Alfvén waves strongly suppresses the beam instabilities.. |

37. |
T. Matsuoka, T. S. Rudenko, I. Funaki, K. P. Shamrai, T. Nakamura, H. Nishida, T. Tanikawa, T. Hada, S. Shinohara, One Dimensional Modeling of Radio Frequency Electric Field Penetration into Magnetized Plasmas, *Jpn. J. Appl. Phys.*, 51, 6, doi. 096201, 2012.06. |

38. |
H. Nishida, T. Nakamura, K. Takahashi, S. Shinohara, T. Matsuoka, I. Funaki, T. Tanikawa, T. Hada, K. P. Shamrai, Study on Proof-of-Principle of Lissajous Acceleration for Electrodeless Helicon Plasma Thruster, *Frontier of Applied Plasma Technology*, 5, 2, 67, 2012.05. |

39. |
T. Nakamura, K. Takahashi, H. Nishida, S. Shinohara, T. Matsuoka, I. Funaki, T. Tanikawa, T. Hada, Experimental Investigation of Electromagnetic Plasma Acceleration by Rotating Electric Field, *World Academy of Science, Engineering and Technology*, 71, 797-801, 2012.04. |

40. |
S. Shinohara, T. Hada, O. Kaneko, K. Tsumori, Development of High-Density Helicon Plasma Source with Large Diameter and Low Aspect Ratio for Negative Ion NBI, *Annual Rep. of National Institute for Fusion Sci.*, 179, 2012.03. |

41. |
S. Shinohara, T. Hada, M. Ichimura, R. Ikezoe, T. Yokoyama, Y. Ugajin, Basic Study on Generation and Control of High-Density Plasma Flow in the Plasma Edge, *Annual Rep. of National Institute for Fusion Sci.*, 480, 2012.03. |

42. |
Tohru Hada, Yasuhiro Nariyuki, Marty Lee, Fluid modeling of Short Large Amplitude Magnetic Structures (SLAMs) near the earth's bowshock, *Proceedings to the Plasma Conference 2011, 22E04, CD-ROM
*, 2011.11, The so-called Short Large Amplitude Magnetic Structures (SLAMS) are one of the most outstanding features frequently observed upstream of the earth's bowshock. Although the properties of these structures have been studied extensively using spacecraft observations, the mechanism leading to their formation still remains unclear. Since the SLAMS grow in a region with a gradient of energetic ions, the ion heat flux is likely to be the main energy source for their growth. We model their evolution using the Landau-fluid type framework, by including a nonlocal interaction between the ion heat flux and the magnetic envelope modulation. Numerical simulations show that, in the presence of inverse Landau interaction, a series of magnetic pulsations similar to the SLAMS grow rapidly. The growth is nonlinear and singular. . |

43. |
T. Matsuoka, S. Satoh, I. Funaki, T. Nakamura, S. Shinohara, H. Nishida, K. Yokoi, T. S. Rudenko, K. P. Shamrai, T. Hada, T. Tanikawa, T. Fujino, Preliminary thrust measurement in development of long lifetime helicon plasma rockets by use of Lissajous method , *Proceedings to the Plasma Conference 2011, 24E12, CD-ROM*, 2011.11, A thrust model by use of a Lissajous method has shown that these rocket has potentially longer lifetime with better performance compared with the rockets using, e.g., ion engines. Previous experiments showed a slight increase of plasma flow velocity by the method, however, experimental conditions were not optimized and the thrust was not measured. In this study, in order to develop helicon plasma sources and thrust measurement method, a thrust is measured from a 26 mm diameter helicon plasma rocket without Lissajous method. A design of laboratory models for plasma rockets in order to verify the thrust model is also presented based on experimental findings. . |

44. |
T. Nakamura, K. Yokoi, H. Nishida, T. Matsuoka, I. Funaki, S. Shinohara, T. Tanikawa, T. Hada, T. Motomura, K. P. Shamrai, T. S. Rudenko, Study on Helicon Plasma Lissajous Acceleration for Electrodeless Electric Propulsion, *Proc. to 29th International Symposium on Space Technology and Science, b-08, 2011*, 2011.08, In order to realize a long lifetime of an electric propulsion system, we have been investigating various electrodeless electric propulsion concepts utilizing a helicon plasma source. In one of our concepts, helicon plasma is electromagnetically accelerated using a rotating electric field in the presence of a diverging static magnetic field. This acceleration concept is called the Lissajous acceleration. Plasma acceleration experiments have been conducted and plasma acceleration was evaluated using a Mach probe. Although the experiments showed some features of the electromagnetic acceleration, most increment of the plasma velocity is caused by the increment of the electron temperature. The thrust (4.95 μN) has not reached feasible values for real applications, and therefore, it is important to find a better operational condition with the aid of a theoretical thrust model. We have developed a theoretical thrust model which consists of a trajectory analysis and an electric field penetration model in the electrostatic approximation. The model shows that experimental parameters are off from an optimum operational condition which provides the maximum thrust.. |

45. |
T. Matsuoka, T. Nakamura, K. Yokoi, T. S. Rudenko, I. Funaki, H. Nishida, K. P. Shamrai, T. Tanikawa, T. Hada, S. Shinohara
, Electric field penetration in electrodeless helicon plasma thruster, *Proc. to 29th International Symposium on Space Technology and Science, b-09, 2011*, 2011.08, The Lissajous Helicon Plasma Accelerator (LHPA) has been studied as an electrodeless plasma thruster. In the LHPA, a rotating electric field (REF) in an external longitudinal magnetic field drives the azimuthal current via E×B drift. The thrust is produced due to the Lorentz force in a diverging magnetic field, which accelerates a helicon plasma. Among the issues of the LHPA, the REF penetration into the plasma is critical since thrust depends on the strength of the REF in the plasma. A 1D analytical model is developed for field penetration and compared with 1D particle in cell simulations by use of the code VORPAL. The electrical field from the model was found to be consistent with the simulation results. The influence of the REF penetration to the thrust will be discussed.. |

46. |
T. Matsuoka, T. Nakamura, K. Yokoi, T. S. Rudenko, I. Funaki, H. Nishida, K. P. Shamrai, T. Tanikawa, T. Hada, S. Shinohara
, Electric field penetration in electrodeless helicon plasma thruster, *Proc. to 29th International Symposium on Space Technology and Science, b-09, 2011*, 2011.08, The Lissajous Helicon Plasma Accelerator (LHPA) has been studied as an electrodeless plasma thruster. In the LHPA, a rotating electric field (REF) in an external longitudinal magnetic field drives the azimuthal current via E×B drift. The thrust is produced due to the Lorentz force in a diverging magnetic field, which accelerates a helicon plasma. Among the issues of the LHPA, the REF penetration into the plasma is critical since thrust depends on the strength of the REF in the plasma. A 1D analytical model is developed for field penetration and compared with 1D particle in cell simulations by use of the code VORPAL. The electrical field from the model was found to be consistent with the simulation results. The influence of the REF penetration to the thrust will be discussed.. |

47. |
Y. Nariyuki, T. Umeda, T. Kumashiro, T. Hada, A new numerical method for simulating the solar wind Alfvén waves: Development of the Vlasov-MHD model, *Planetary and Space Science*, 10.1016/j.pss.2011.02.017, 59, 8, 767-771, 2011.06. |

48. |
T. Matsuoka, I. Funaki, T. Nakamura, K. Yokoi, H. Nishida, T. S. Rudenko, K. P. Shamrai, T. Tanikawa, T. Hada, S. Shinohara, Scaling Laws of Lissajous Acceleration for Electrodeless Helicon Plasma Thruster, *Plasma and Fusion Research*, 2406103, 6, 2406103-1, 2011.06, Analytical thrust model for the Lissajous Helicon Plasma Accelerator (LHPA) is developed by extending previous works [1, 2] in order to guide experiments for achieving feasible value of the thrust. In the LHPA, a rotating transverse electric field in an external divergent magnetic field drives azimuthal currents via electron E × B drift then the thrust is produced due to the Lorentz force. One dimensional (1D) analytical model is developed which includes the electric field penetration into the plasma and the E × B current estimation based on a trajectory analysis. Thrust as a function of parameters of the plasma density and the magnetic field is studied. The penetration of the electrical field into plasmas is examined by 1D particle in cell (PIC) simulations whose results are consistent with those of the 1D analytical model.. |

49. |
K. Meziane, A. Hamza, M. Wilber, M. A. Lee, C. Mazelle, E. A. Lucek, T. Hada, Specular refection at a non-stationary shock: A simple model, *Planetary and Space Science*, 10.1016/j.pss.2010.10.016, 59, 7, 495-501, 2011.05. |

50. |
Takeshi Matsuoka, Ikkoh Funaki, Takahiro Nakamura, Kenji Yokoi, Hiroyuki Nishida, Timofei S. Rudenko, Konstantin P. Shamrai, Takao Tanikawa, Tohru Hada, Shunjiro Shinohara, Scaling laws of lissajous acceleration for electrodeless helicon plasma thruster, *Plasma and Fusion Research*, 10.1585/pfr.6.2402103, 6, 1 SPECIAL ISSUE, 2011, Analytical thrust model for the Lissajous Helicon Plasma Accelerator (LHPA) is developed by extending previous works [1,2] in order to guide experiments for achieving feasible value of the thrust. In the LHPA, a rotating transverse electric field in an external divergent magnetic field drives azimuthal currents via electron E × B drift then the thrust is produced due to the Lorentz force. One dimensional (1D) analytical model is developed which includes the electric field penetration into the plasma and the E × B current estimation based on a trajectory analysis. Thrust as a function of parameters of the plasma density and the magnetic field is studied. The penetration of the electrical field into plasmas is examined by 1D particle in cell (PIC) simulations whose results are consistent with those of the 1D analytical model.. |

51. |
Y. Nariyuki, T. Hada, K. Tsubouchi, Heating and acceleration of ions in nonresonant Alfvénic turbulence, *Physics of Plasmas*, 10.1063/1.3449592, 17, 7, 072301-072301-5, 2010.07. |

52. |
K. Meziane, A. Hamza, M. Wilber, M. A. Lee, C. Mazelle, E. A. Lucek, T. Hada, A. Markowitch, Effect of Shock Normal Orientation Fluctuations on Field-Aligned Beam Distributions, *Astrophysics and Space Science Proceedings*, 10.1007/978-90-481-3499-1 23, 349-362, 2010.01. |

53. |
K. Meziane, A. M. Hamza, M. Wilber, M. A. Lee, C. Mazelle, E. A. Lucek, Tohru Hada, A. Markowitch, Effect of shock normal orientation fluctuations on field-aligned beam distributions, *Astrophysics and Space Science Proceedings*, 10.1007/978-90-481-3499-1_23, 202469, 349-362, 2010.01, We address the unsolved question of how foreshock field-aligned beam (FAB) parallel temperatures are produced. Studies including numerical simulations and recent observations have indicated that shocks can be nonstationary and include embedded spatial structures with varied scales. As a first step towards assessing the impact of such variability on backstreaming ions, we examine how a randomly distributed shock normal direction will affect FAB parallel velocity (v_{||}) distributions. Assuming that the FABs are produced in a quasi-adiabatic reflection process at the shock, we derive a probability distribution function for v_{||}. These derived distributions exhibit second, third and fourth order moments that agree well with the observations for a large range of reflection efficiencies δ, and depend strongly upon the average angle between the magnetic field and the shock normal θ_{Bn0}. Best agreement is obtained for fluctuations of the normal orientation of a few degrees about a nominal direction. The derived model predicts a strong correlation between the shock geometry (θ_{Bn0}) and the moments of the parallel velocity distribution, but with stronger tails extending to higher values of θ_{Bn0}, a trend opposite to the observations.. |

54. |
F. Asenjo, V. Munoz, J. Valdivia, T. Hada, Circularly polarized wave propagation in magnetofluid dynamics for relativistic electron-positron plasmas, *Physics of Plasmas*, 16, 12, 122108-122108-5, 2009.12. |

55. |
Felipe A. Asenjo, Víctor Muoz, Juan Alejandro Valdivia, Tohru Hada, Circularly polarized wave propagation in magnetofluid dynamics for relativistic electron-positron plasmas, *Physics of Plasmas*, 10.1063/1.3272667, 16, 12, 2009.12, The dispersion relation for circularly polarized electromagnetic waves propagating in the direction of an external magnetic field in a relativistic electron-positron plasma with arbitrary constant drift velocities is obtained for constant temperature in the homentropic regime. This result is an exact solution of the nonlinear magnetofluid unification field formalism introduced by S. Mahajan [Phys. Rev. Lett. 90, 035001 (2003)], where the electromagnetic and fluid fields are coupled through the relativistic enthalpy density. The behavior of electromagnetic and Alfv́n branches of the dispersion relation are discussed for different temperatures.. |

56. |
Y. Nariyuki, T. Hada, K. Tsubouchi, Parametric instabilities of circularly polarized Alfvén waves in plasmas with beam protons, *Journal of Geophysical Research*, 10.1029/2009JA014178, 2009.07. |

57. |
F. Otsuka and T. Hada, Cross-field diffusion of cosmic rays in two-dimensional magnetic field turbulence models, *The Astrophysical Journal*, vol. 697, issue 1, pp. 886-899, 2009.05. |

58. |
S. Shinohara, T. Hada, T. Motomura, K. Tanaka, T. Tanikawa, K. Toki, Y. Tanaka, K. P. Shamrai, Development of high-density helicon plasma sources and their applications, *Physics of Plasmas*, 10.1063/1.3096787, 16, 5, 057104-057104-10, 2009.05. |

59. |
G. Sánchez-Arriaga, Tohru Hada, Y. Nariyuki, The truncation model of the derivative nonlinear Schrödinger equation, *Physics of Plasmas*, 10.1063/1.3093383, 16, 4, 2009.05, The derivative nonlinear Schrödinger (DNLS) equation is explored using a truncation model with three resonant traveling waves. In the conservative case, the system derives from a time-independent Hamiltonian function with only one degree of freedom and the solutions can be written using elliptic functions. In spite of its low dimensional order, the truncation model preserves some features from the DNLS equation. In particular, the modulational instability criterion fits with the existence of two hyperbolic fixed points joined by a heteroclinic orbit that forces the exchange of energy between the three waves. On the other hand, numerical integrations of the DNLS equation show that the truncation model fails when wave energy is increased or left-hand polarized modulational unstable modes are present. When dissipative and growth terms are added the system exhibits a very complex dynamics including appearance of several attractors, period doubling bifurcations leading to chaos as well as other nonlinear phenomenon. In this case, the validity of the truncation model depends on the strength of the dissipation and the kind of attractor investigated.. |

60. |
G. Sanchez-Arriaga, T. Hada, Y. Nariyuki, The truncation model of the derivative nonlinear Schroedinger equation, *Physics of Plasmas*, vol. 16, issue 4, pp. 042302-042302-8, 2009.04. |

61. |
G. Sanchez-Arriaga, T. Hada, Y. Nariyuki, Truncation model of in the triple-degenerate derivative nonlinear Schroedinger equation, *Physics of Plasmas*, vol. 16, issue 4, pp. 042303-042303-9, 2009.04. |

62. |
S. Matsukiyo and T. Hada, Relativistic particle acceleration in developing Alfven turbulence, *The Astrophysical Journal*, vol. 692, issue 2, pp. 1004-1012, 2009.02. |

63. |
Shuichi Matsukiyo, Tohru Hada, Relativistic particle acceleration in developing Alfvén turbulence, *Astrophysical Journal*, 10.1088/0004-637X/692/2/1004, 692, 2, 1004-1012, 2009.02, A new particle acceleration process in a developing Alfvén turbulence in the course of successive parametric instabilities of a relativistic pair plasma is investigated by utilizing one-dimensional electromagnetic full particle code. Coherent wave-particle interactions result in efficient particle acceleration leading to a power-law-like energy distribution function. In the simulation, high-energy particles having large relativistic masses are preferentially accelerated as the turbulence spectrum evolves in time. The main acceleration mechanism is simultaneous relativistic resonance between a particle and two different waves. An analytical expression of maximum attainable energy in such wave-particle interactions is derived.. |

64. |
G. Sánchez-Arriaga, Tohru Hada, Y. Nariyuki, Truncation model in the triple-degenerate derivative nonlinear Schrödinger equation, *Physics of Plasmas*, 10.1063/1.3093394, 16, 4, 2009.01, The triple-degenerate derivative nonlinear Schrödinger (TDNLS) system modified with resistive wave damping and growth is truncated to study the coherent coupling of four waves, three Alfven and one acoustic, near resonance. In the conservative case, the truncation equations derive from a time independent Hamiltonian function with two degrees of freedom. Using a Poincare map analysis, two parameters regimes are explored. In the first regime we check how the modulational instability of the TDNLS system affects to the dynamics of the truncation model, while in the second one the exact triple degenerated case is discussed. In the dissipative case, the truncation model gives rise to a six dimensional flow with five free parameters. Computing some bifurcation diagrams the dependence with the sound to Alfven velocity ratio as well as the Alfven modes involved in the truncation is analyzed. The system exhibits a wealth of dynamics including chaotic attractor, several kinds of bifurcations, and crises. The truncation model was compared to numerical integrations of the TDNLS system.. |

65. |
F. Otsuka, Tohru Hada, Cross-field diffusion of cosmic rays in two-dimensional magnetic field turbulence models, *Astrophysical Journal*, 10.1088/0004-637X/697/1/886, 697, 1, 886-899, 2009, We discuss cross-field diffusion of energetic particles using compressional and noncompressional two-dimensional turbulence models by performing test particle simulations. For both models, the diffusion coefficient, defined in the classical way, exhibits a timescale dependence, suggesting that the underlining physical process should be described by Lévy statistics. The diffusion coefficient for long timescales is classified in terms of the Kubo number, K = bL /ρ, where b is the standard deviation of magnetic field fluctuation in units of the background field, ρ is the particle Larmor raduis, and L is the field turbulence scale length. While the well-known JKG theorem predicts that a particle cannot move more than about one gyroradius normal to the magnetic field in a system with two or less spatial dimensions, the cross-field diffusion does take place in our models since they are exceptions to the theorem: we argue that particle motion on the flux surface is not prohibited in general, and in particular, it is not bounded when the background magnetic field is exactly parallel to the ignorable coordinate.. |

66. |
Y. Nariyuki, Tohru Hada, K. Tsubouchi, On nonlinear evolution of Alfv́nic turbulence in low beta plasmas, *Physics of Plasmas*, 10.1063/1.3028316, 15, 11, 2008.12, Nonlinear evolution of broadband spectrum Alfv́nic turbulence is studied by using one-dimensional hybrid simulations. Numerical solutions indicate that the important characteristics in the solar wind magnetohydrodynamic (MHD) turbulence are naturally reproduced by nonlinear evolution of Alfv́nic turbulence with more realistic power spectrum than one used in the past studies. Namely, (i) the modulational instability can dissipate the magnetic energy of Alfv́nic turbulence and preserve the Alfv́nicity even in low beta plasmas. (ii) Nonlinear evolution of the Alfv́nic turbulence can induce the generation of the localized structures in the solar wind MHD turbulence.. |

67. |
Y. Nariyuki, T. Hada, K. Tsubouchi, On nonlinear evolution of Alfvenic turbulence in low beta plasmas, *Phys. Plasmas*, vol. 15, no. 11, pp. 114502-114504, 2008.11. |

68. |
Y. Narita, K.-H. Glassmeier, P. M. E. Decreau, T. Hada, U. Motschmann, Y. Nariyuki, Evaluation of bispectrum in the wave number domain based on multi-point measurements, *Ann. Geophys.*, vol. 26, no.11, pp. 3389-3393, 2008.10. |

69. |
Y. Nariyuki, S. Matsukiyo, T. Hada, Parametric instabilities of large-amplitude parallel propagating Alfven waves: 2D PIC simulation, *New Journal of Physics*, vol. 10, doi. 083004, 2008.08. |

70. |
Y. Nariyuki, Shuichi Matsukiyo, Tohru Hada, Parametric instabilities of large-amplitude parallel propagating Alfvén waves 2D PIC simulation, *New Journal of Physics*, 10.1088/1367-2630/10/8/083004, 10, 2008.08, We discuss the parametric instabilities of large-amplitude parallel propagating Alfvén waves using the 2D PIC simulation code. First, we confirmed the results from a previous study (Sakai et al 2005 New J, Phys. 7 233) that the electrons are heated due to the modified two-stream instability and that the ions are heated by the parallel propagating ion acoustic waves. However, although the past study argued that such parallel propagating longitudinal waves are excited by transverse modulation of the parent Alfvén wave, we consider these waves are more likely to be generated by the usual, parallel decay instability. Further, we performed other simulation runs with different polarization of the parent Alfvén waves or different ion thermal velocity. Numerical results suggest that electron heating by the modified two-stream instability due to the large amplitude Alfvén waves is unimportant with most parameter sets.. |

71. |
Y. Kuramitsu and T. Hada, Nonadiabatic interaction between a charged particle and an MHD pulse, *Nonlin. Proc. Geophys.*, vol. 15, no. 2, pp. 265-273, 2008.03. |

72. |
D. Koga, A. C. -L. Chian, T. Hada, E. L. Rempel, Experimental evidence of phase coherence of magnetohydrodynamic turbulence in the solar wind: GEOTAIL satellite data, *Phil. Trans. Royal Soc. A*, vol. 366, no. 1864, pp. 447-457, 2008.02. |

73. |
D. Koga, A. C L Chian, Tohru Hada, E. L. Rempel, Experimental evidence of phase coherence of magnetohydrodynamic turbulence in the solar wind GEOTAIL satellite data, *Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences*, 10.1098/rsta.2007.2102, 366, 1864, 447-457, 2008.02, Magnetohydrodynamic (MHD) turbulence is commonly observed in the solar wind. Nonlinear interactions among MHD waves are likely to produce finite correlation of the wave phases. For discussions of various transport processes of energetic particles, it is fundamentally important to determine whether the wave phases are randomly distributed (as assumed in the quasi-linear theory) or have a finite coherence. Using a method based on the surrogate data technique, we analysed the GEOTAIL magnetic field data to evaluate the phase coherence in MHD turbulence in the Earth's foreshock region. The results demonstrate the existence of finite phase correlation, indicating that nonlinear wave-wave interactions are in progress.. |

74. |
Y. Narita, K. H. Glassmeier, P. M.E. Dãcrãau, Tohru Hada, U. Motschmann, Y. Nariyuki, Evaluation of bispectrum in the wave number domain based on multi-point measurements, *Annales Geophysicae*, 10.5194/angeo-26-3389-2008, 26, 11, 3389-3393, 2008.01, We present an estimator of the bispectrum, a measure of three-wave couplings. It is evaluated directly in the wave number domain using a limited number of detectors. The ability of the bispectrum estimator is examined numerically and then it is applied to fluctuations of magnetic field and electron density in the terrestrial foreshock region observed by the four Cluster spacecraft, which indicates the presence of a three-wave coupling in space plasma.. |

75. |
Y. Kuramitsu, Tohru Hada, Nonadiabatic interaction between a charged particle and an MHD pulse, *Nonlinear Processes in Geophysics*, 15, 2, 265-273, 2008, Interaction between a magnetohydrodynamic∼(MHD) pulse and a charged particle is discussed both numerically and theoretically. Charged particles can be accelerated efficiently in the presence of spatially correlated MHD waves, such as short large amplitude magnetic structures, by successive mirror reflection (Fermi process). In order to understand this process, we study the reflection probability of particles by the MHD pulses, focusing on the adiabaticity on the particle motion. When the particle velocity is small (adiabatic regime), the probability that the particle is reflected by the MHD pulse is essentially determined only by the pitch angle, independent from the velocity. On the other hand, in the non-adiabatic regime, the reflection probability is inversely proportional to the square root of the normalized velocity. We discuss our numerical as well as analytical results of the interaction process with various pulse amplitude, pulse shape, and the pulse winding number. The reflection probability is universally represented as a power law function independent from above pulse properties.. |

76. |
Y. Nariyuki, T. Hada, K. Tsubouchi, Parametric instabilities of parallel propagating incoherent Alfven waves in a finite ion beta plasma, *Physics of Plasmas*, vol. 14, issue 12, pp. 122110-122110-9, 2007.12. |

77. |
Y. Nariyuki, Tohru Hada, K. Tsubouchi, Parametric instabilities of parallel propagating incoherent Alfv́n waves in a finite ion beta plasma, *Physics of Plasmas*, 10.1063/1.2824986, 14, 12, 2007.12, Large amplitude, low-frequency Alfv́n waves constitute one of the most essential elements of magnetohydrodynamic (MHD) turbulence in the fast solar wind. Due to small collisionless dissipation rates, the waves can propagate long distances and efficiently convey such macroscopic quantities as momentum, energy, and helicity. Since loading of such quantities is completed when the waves damp away, it is important to examine how the waves can dissipate in the solar wind. Among various possible dissipation processes of the Alfv́n waves, parametric instabilities have been believed to be important. In this paper, we numerically discuss the parametric instabilities of coherent/incoherent Alfv́n waves in a finite ion beta plasma using a one-dimensional hybrid (superparticle ions plus an electron massless fluid) simulation, in order to explain local production of sunward propagating Alfv́n waves, as suggested by Helios/Ulysses observation results. Parameter studies clarify the dependence of parametric instabilities of coherent/incoherent Alfv́n waves on the ion and electron beta ratio. Parametric instabilities of coherent Alfv́n waves in a finite ion beta plasma are vastly different from those in the cold ions (i.e., MHD and/or Hall-MHD systems), even if the collisionless damping of the Alfv́n waves are neglected. Further, "nonlinearly driven" modulational instability is important for the dissipation of incoherent Alfv́n waves in a finite ion beta plasma regardless of their polarization, since the ion kinetic effects let both the right-hand and left-hand polarized waves become unstable to the modulational instability. The present results suggest that, although the antisunward propagating dispersive Alfv́n waves are efficiently dissipated through the parametric instabilities in a finite ion beta plasma, these instabilities hardly produce the sunward propagating waves.. |

78. |
T. Terasawa, T. Hada, S. Matsukiyo, M. Oka, A. Bamba, R. Yamazaki, Shock Modification by Cosmic-Ray-Excited Turbulences, *Prog. Theor. Phys. Suppl.*, No. 169, pp. 146-149, 2007.11. |

79. |
Y. Nariyuki, Tohru Hada, Consequences of finite ion temperature effects on parametric instabilities of circularly polarized Alfvén waves, *Journal of Geophysical Research*, 10.1029/2007JA012373, 112, 10, 2007.10, Parametric instabilities of finite amplitude, circularly polarized, parallel propagating Alfvén waves in a homogeneous plasma is discussed analytically, taking into account the ion Landau damping and the ion finite Larmor radius (FLR) effects. A hybrid kinetic fluid model is systematically derived from one-dimensional Vlasov equation for longitudinal ion motion and the FLR-Hall magnetohydrodynamic (MHD) equations for transverse directions. The longitudinal kinetic effects are retained in the model, whereas transverse kinetic effects such as ion cyclotron damping is neglected. Validity of the model is justified as far as the collisionless damping is concerned, since the ion cyclotron damping for typical quasi-parallel Alfvén waves in the solar wind is considered to be negligibly small. As already shown in a number of past studies, inclusion of the kinetic effects let some new instabilities emerge, while that reduces the growth rates of fluid instabilities in general. Damping rates computed by a model using collision-like (local) damping terms deviate from results of the present model, suggesting the importance of using the exact Landau-type interactions. Furthermore, as a consequence of the FLR effects, the growth rates of the fluid decay and beat instabilities of the left-hand (right-hand) polarized mode are reduced more strongly (weakly) in the FLR-Hall-MHD model (FHM model) than in the Hall-MHD model (HM model). A hybrid simulation is carried out to confirm that the FHM model is in better agreement than the HM model with the simulation results. When the initial parent wave amplitude is relatively small, the simulation results quantitatively agree with the linear analysis. Furthermore, some arguments are given to the observed ion relaxation and the energy oscillation of the parent waves observed in the hybrid simulations. Here again, quantitatively better explanation is obtained by using the FHM model rather than the HM model, suggesting that it is important to include the FLR effects for correctly describing the Alfvén wave parametric instabilities in finite ion beta plasmas, such as the solar wind near the Earth and the foreshock plasma.. |

80. |
Y. Nariyuki and T. Hada, Density fluctuations induced by modulational instability of parallel propagating Alfven waves with beta_f sim 1, *Journal of the Physical Society of Japan*, 印刷中, 2007.09. |

81. |
Y. Nariyuki and T. Hada, Consequences of finite ion temperature effects on parametric instabilities of circularly polarized Alfven waves, *Journal of Geophysical Research*, 印刷中, 2007.09. |

82. |
A. L. Chian, W. M. Santana, E. L. Rempel, F. A. Borott, T. Hada, Y. Kamide, Chaos in driven Alfven systems: unstable periodic orbits and chaotic saddles, *Nonl. Proc. in Geophys.*, vol. 14, no. 1, pp. 17-29, 2007.07. |

83. |
Yasuhiro Nariyuki, Tohru Hada, Density fluctuations induced by modulational instability of parallel propagating Alfvén waves with β _{f} ∼ 1, *Journal of the Physical Society of Japan*, 10.1143/JPSJ.76.074901, 76, 7, 2007.07, Density fluctuations generated by envelope modulation of Alfvén waves are studied when the sound to Alfvén velocity ratio C _{s}/C _{A} (≡ √β _{f}) ∼ 1, using a kinetic version of the triple-degenerate derivative nonlinear Schrödinger (TDNLS) equation set, in which both right- and left-hand polarized quasi-parallel Alfvén waves as well as sound waves, all propagating in the same direction, are included. In the model, kinetic effects along the longitudinal direction are introduced phenomenologically. Long time evolution of the Alfvén waves are discussed by numerically time integrating the obtained TDNLS model. The TDNLS model reproduces not only features of the well-known derivative nonlinear Schrödinger (DNLS) model, but also results obtained from more general frameworks. Numerical results suggest that the nonlinearly-driven modulational instability can play important roles in the dissipation of both right- and left-hand polarized Alfvén waves in the solar wind.. |

84. |
Y. Nariyuki and T. Hada, Magnetohydrodynamic parametric instabilities of parallel propagating incoherent Alfven waves, *Earth, Planets and Space*, vol. 59, e13-16, 2007.04. |

85. |
Y. Nariyuki and T. Hada, Response to "Comment on 'Kinetically modified parametric instabilities of circularly polarized Alfven waves: Ion kinetic effects'", *Physics of Plasmas*, vol. 14, doi. 024704, 2007.01. |

86. |
A. C.L. Chian, W. M. Santana, E. L. Rempel, F. A. Borotto, Tohru Hada, Y. Kamide, Chaos in driven Alfvén systems Unstable periodic orbits and chaotic saddles, *Nonlinear Processes in Geophysics*, 10.5194/npg-14-17-2007, 14, 1, 17-29, 2007.01, The chaotic dynamics of Alfvén waves in space plasmas governed by the derivative nonlinear Schrödinger equation, in the low-dimensional limit described by stationary spatial solutions, is studied. A bifurcation diagram is constructed, by varying the driver amplitude, to identify a number of nonlinear dynamical processes including saddle-node bifurcation, boundary crisis, and interior crisis. The roles played by unstable periodic orbits and chaotic saddles in these transitions are analyzed, and the conversion from a chaotic saddle to a chaotic attractor in these dynamical processes is demonstrated. In particular, the phenomenon of gap-filling in the chaotic transition from weak chaos to strong chaos via an interior crisis is investigated. A coupling unstable periodic orbit created by an explosion, within the gaps of the chaotic saddles embedded in a chaotic attractor following an interior crisis, is found numerically. The gap-filling unstable periodic orbits are responsible for coupling the banded chaotic saddle (BCS) to the surrounding chaotic saddle (SCS), leading to crisis-induced intermittency. The physical relevance of chaos for Alfvén intermittent turbulence observed in the solar wind is discussed.. |

87. |
Y. Narita, K. H. Glassmeier, M. Fränz, Y. Nariyuki, Tohru Hada, Observations of linear and nonlinear processes in the foreshock wave evolution, *Nonlinear Processes in Geophysics*, 10.5194/npg-14-361-2007, 14, 4, 361-371, 2007.01, Waves in the foreshock region are studied on the basis of a hypothesis that the linear process first excites the waves and further wave-wave nonlinearities distribute scatter the energy of the primary waves into a number of daughter waves. To examine this wave evolution scenario, the dispersion relations, the wave number spectra of the magnetic field energy, and the dimensionless cross helicity are determined from the observations made by the four Cluster spacecraft. The results confirm that the linear process is the ion/ion right-hand resonant instability, but the wave-wave interactions are not clearly identified. We discuss various reasons why the test for the wave-wave nonlinearities fails, and conclude that the higher order statistics would provide a direct evidence for the wave coupling phenomena.. |

88. |
Toshio Terasawa, Tohru Hada, Shuichi Matsukiyo, Mitsuo Oka, Aya Bamba, Ryo Yamazaki, Shock modification by cosmic-ray-excited turbulences, *Progress of Theoretical Physics*, 10.1143/PTPS.169.146, 169, 146-149, 2007.01, In cosmic-ray-mediated shocks large amplitude Alfvén waves are believed to be generated by accelerated cosmic ray particles. The enhanced magnetic pressure shared by these waves is non-negligible in the momentum and energy balances across the shock transition region. Accordingly the shock Rankine-Hugoniot condition is further modified, and the compression ratio across the shock departs from the classical values of 4 (nonrelativistic) and 7 (relativistic). We argue that in the 'grand equipartition' limit, namely equipartition among the waves, the background plasma, and the cosmic ray particles, the compression ratio recovers to the value of 4, and the corresponding spectral index of cosmic ray particles also comes back to the canonical value of 2.. |

89. |
Yasuhiro Nariyuki, Tohru Hada, Magnetohydrodynamic parametric instabilities of parall propagating incoherent Alfvén waves, *Earth, Planets and Space*, 59, 12, 2007, Numerical experiments for parametric instabilities of incoherent Alfvén waves in the context of one dimensional Hall-MHD equation sets are studied. The reason why the decay instability of incoherent waves can be explained in terms of that of the coherent wave is understood through analysis on nonlinearly driven finite amplitude density fluctuations. Numerical results suggest the importance of modulational instabilities of left-hand polarized Alfvén waves.. |

90. |
Y. Nariyuki, Tohru Hada, Response to "comment on Kinetically modified parametric instabilities of circularly polarized Alfv́n waves Ion kinetic effects' " [Phys. Plasmas 14, 024703 (2007)], *Physics of Plasmas*, 10.1063/1.2458942, 14, 2, 2007. |

91. |
F. Otsuka and T. Hada, Anomalous diffusion of cosmic rays in magnetic field turbulence - Linkage between diffusion statistics and turbulence statistics, *Progress in Theoretical Physics, supplement*, no. 162, pp.204-211, 2006.12. |

92. |
Y. Nariyuki and T. Hada, Kinetically modified parametric instabilities of circularly polarized Alfven waves: Ion kinetic effects, *Physics of Plasmas*, vol 13 (12), doi. 124501, 2006.12. |

93. |
V. Munoz, T. Hada, S. Matsukiyo, Kinetic effects on the parametric decays of Alfven waves in relativistic pair plasmas, *Earth, Planets, and Space*, vol. 58 (9), pp. 1213-1217, 2006.09. |

94. |
Y. Nariyuki and T. Hada, Remarks on nonlinear relation among phases and frequencies in modulational instabilities of parallel propagating Alfven waves, *Nonlinear Processes in Geophysics*, vol. 13, pp. 425-441, 2006.04. |

95. |
V. Muñoz, Tohru Hada, Shuichi Matsukiyo, Kinetic effects on the parametric decays of Alfv én waves in relativistic pair plasmas, *Earth, Planets and Space*, 10.1186/BF03352012, 58, 9, 1213-1217, 2006.01, Parametric decays of a circularly polarized wave propagating along a constant magnetic field in an electron-positron plasma are studied. Fully relativistic effects on the particle velocity in the wave field are considered, as well as kinetic effects in the parallel direction, by means of a one-dimensional relativistic Vlasov equation. In this approximation, a dispersion relation is found for the parametric decays which describes the coupling between normal modes of the system, namely electromagnetic sideband modes and Langmuir waves.. |

96. |
Y. Nariyuki, Tohru Hada, Remarks on nonlinear relation among phases and frequencies in modulational instabilities of parallel propagating Alfvén waves, *Nonlinear Processes in Geophysics*, 10.5194/npg-13-425-2006, 13, 4, 425-441, 2006.01, Nonlinear relations among frequencies and phases in modulational instability of circularly polarized Alfvén waves are discussed, within the context of one dimensional, dissipation-less, unforced fluid system. We show that generation of phase coherence is a natural consequence of the modulational instability of Alfvén waves. Furthermore, we quantitatively evaluate intensity of wave-wave interaction by using bi-coherence, and also by computing energy flow among wave modes, and demonstrate that the energy flow is directly related to the phase coherence generation. We first discuss the modulational instability within the derivative nonlinear Schrödinger (DNLS) equation, which is a subset of the Hall-MHD system including the right- and left-hand polarized, nearly degenerate quasi-parallel Alfvén waves. The dominant nonlinear process within this model is the four wave interaction, in which a quartet of waves in resonance can exchange energy. By numerically time integrating the DNLS equation with periodic boundary conditions, and by evaluating relative phase among the quartet of waves, we show that the phase coherence is generated when the waves exchange energy among the quartet of waves. As a result, coherent structures (solitons) appear in the real space, while in the phase space of the wave frequency and the wave number, the wave power is seen to be distributed around a straight line. The slope of the line corresponds to the propagation speed of the coherent structures. Numerical time integration of the Hall-MHD system with periodic boundary conditions reveals that, wave power of transverse modes and that of longitudinal modes are aligned with a single straight line in the dispersion relation phase space, suggesting that efficient exchange of energy among transverse and longitudinal wave modes is realized in the Hall-MHD. Generation of the longitudinal wave modes violates the assumptions employed in deriving the DNLS such as the quasi-static approximation, and thus long time evolution of the Alfvén modulational instability in the DNLS and in the Hall-MHD models differs significantly, even though the initial plasma and parent wave parameters are chosen in such a way that the modulational instability is the most dominant instability among various parametric instabilities. One of the most important features which only appears in the Hall-MHD model is the generation of sound waves driven by ponderomotive density fluctuations. We discuss relationship between the dispersion relation, energy exchange among wave modes, and coherence of phases in the waveforms in the real space. Some relevant future issues are discussed as well.. |

97. |
Fumiko Otsuka, Tohru Hada, Anomalous diffusion of cosmic rays in magnetic field turbulence - Linkage between diffusion statistics and turbulence statistics, *Progress of Theoretical Physics*, 10.1143/PTPS.162.204, 162, 204-211, 2006, Anomalous diffusion of energetic charged particles (cosmic rays) is studied using a simple two-dimensional cross field diffusion model. Both super-diffusion and sub-diffusion can take place in the model. When typical Larmor radius of the particles is much less than the field correlation length, the particles essentially gradient-B drift along equi-contour lines of the magnetic field strength, and thus the diffusion in this parameter regime can essentially be understood by analyzing statistics of the magnetic field islands composed of these equi-contour lines. We numerically evaluate the statistics of the field islands such as the probability distribution function of island radius and fractal dimension of the island contour lines, as functions of the power-law index of the magnetic field turbulence. We find numerically and analytically the scaling laws of time-scale dependent diffusion coefficients using the parameters obtained by analysis of the field islands statistics.. |

98. |
Y. Nariyuki, Tohru Hada, Kinetically modified parametric instabilities of circularly polarized Alfv́n waves Ion kinetic effects, *Physics of Plasmas*, 10.1063/1.2399468, 13, 12, 2006, Parametric instabilities of parallel propagating, circularly polarized, finite amplitude Alfv́n waves in a uniform background plasma is studied, within a framework of one-dimensional Vlasov description for ions and massless electron fluid, so that kinetic perturbations in the longitudinal direction (ion Landau damping) are included. The present formulation also includes the Hall effect. The obtained results agree well with relevant analysis in the past, suggesting that kinetic effects in the longitudinal direction play essential roles in the parametric instabilities of Alfv́n waves when the kinetic effects react "passively." Furthermore, existence of the kinetic parametric instabilities is confirmed for the regime with small-wave-number daughter waves. Growth rates of these instabilities are sensitive to ion temperature. The formulation and results demonstrated here can be applied to Alfv́n waves observed in the solar wind and in the earth's foreshock region.. |

99. |
B. T. Tsurutani, F. L. Guarnieri, G. S. Lakhina, T. Hada, Rapid evolution of magnetic decreases (MDs) and discontinuities in the solar wind: ACE and Cluster, *Geophysical Research Letters*, 10.1029/2004GL022151, 32, 10, vol. 32 (10), art. no. L10103, 2005.10. |

100. |
T. Hada, S. Matsukiyo, M. Ikeda, V. Munoz, Dispersion relation and nonlinear evolution of large amplitude relativistic Alfven waves, *Proceedings to the Plasma Science Symposium 2005*, pp. 415-416, 2005.10. |

101. |
Y. Nariyuki, Tohru Hada, Self-generation of phase coherence in parallel Alfv én turbulence, *Earth, Planets and Space*, 10.1186/BF03352580, 57, 6, 2005.01, Nonlinear evolution of Alfven turbulence is discussed within the framework of the derivative nonlinear Schroedinger equation (DNLS), a subset of the hall-MHD equation set, which includes quasi-parallel propagating right-and left-hand polarized Alfv én wave modes. By numerically time integrating the equation with periodic boundary conditions, we discuss relationship between generation of wave phase coherence and self-organization of the system due to birth of Alfv én solitons.. |

102. |
Y. Nariyuki, Tohru Hada, Self-generation of phase coherence in parallel Alfvén turbulence, *Earth, Planets and Space*, 57, 12, 2005, Nonlinear evolution of Alfvén turbulence is discussed within the framework of the derivative nonlinear Schroedinger equation (DNLS), a subset of the hall-MHD equation set, which includes quasi-parallel propagating right- and left-hand polarized Alfvén wave modes. By numerically time integrating the equation with periodic boundary conditions, we discuss relationship between generation of wave phase coherence and self-organization of the system due to birth of Alfvén solitons. Copy right. |

103. |
B. Lembege, J. Giacalone, M. Scholer, T. Hada, M. Hoshino, V. Krasnoselskikh, H. Kucharek, P. Savoini, T. Terasawa, Selected problems in collisionless-shock physics, *Space Science Review*, 10.1023/B:SPAC.0000023372.12232.b7, 110, 3-4, 161-226, vol. 110, no.3-4, pp.161-226, 2004.01. |

104. |
F. A. Borotto, A. C. L. Chian, T. Hada, E. L. Rempel, Chaos in driven Alfven systems: boundary and interior crises, *Physica D*, 10.1016/j.physd.2004.02.014, 194, 3-4, 275-282, vol. 194, no.3-4, pp. 275-282, 2004.01. |

105. |
Field aligned diffusion of charged particles by MHD turbulence: comparison with the quasi-linear theory. |

106. |
Shuichi Matsukiyo, Tohru Hada, Parametric instabilities of circularly polarized Alfvén waves in a relativistic electron-positron plasma, *Physical Review E - Statistical, Nonlinear, and Soft Matter Physics*, 67, 4 2, 464061-4640612, 2003.04, Parametric instabilities of circularly polarized Alfvén waves were discussed. One-dimensional full particle simulation and bicoherence analysis were performed. Results showed that successive decay between the parallel propagating Langmuir-like wave and Alfvén-like wave can generate a continuum of low frequency electromagnetic waves.. |

107. |
S. Matsukiyo, T. Hada, Parametric instabilities of circularly polarized Alfven waves in a relativistic electron-positron plasma, *Phys. Rev. E*, 10.1103/PhysRevE.67.046406, 67, 4, vol. 67, no.4, art. no. 046406, 2003.01. |

108. |
T. Hada, M. Oonishi, B. Lembege, P. Savoini, Shock front nonstationarity of supercritical perpendicular shocks, *J. Geophys. Res.*, 10.1029/2002JA009339, 108, A6, vol. 108, no. A6, art. no. 1233, 2003.01. |

109. |
F. Otsuka, T. Hada, Cross field diffusion of cosmic rays: dependence on 2-d field turbulence models, *AIP conference proceedings*, 669, 808-811, vol. 669, pp.808-811, 2003.01. |

110. |
T. Hada, E. Yamamoto, D. Koga, Phase coherence of large amplitude MHD waves in the earth's foreshock: geotail observations, *AIP conference proceedings*, 669, 840-843, vol.669, pp.840-843, 2003.01. |

111. |
D. Koga, T. Hada, Phase coherence of foreshock MHD waves: Wavelet analysis, *Space Science Review*, 10.1023/A:1025510225311, 107, 1-2, 495-498, vol. 107, no.1-2, pp.495-498, 2003.01. |

112. |
T. Hada, D. Koga, E. Yamamoto, Phase coherence of MHD waves in the solar wind, *Space Science Review*, 10.1023/A:1025506124402, 107, 1-2, 463-466, vol. 107, no.1-2, pp.463-466, 2003.01. |

113. |
F. Otsuka, T. Hada, Cross field diffusion of cosmic rays in a two-dimensional magnetic field turbulene, *Space Science Review*, 10.1023/A:1025562209381, 107, 1-2, 499-502, vol. 107, no.1-2, pp.499-502, 2003.01. |

114. |
T. Hada, F. Otsuka, Y. Kuramitsu, B. T. Tsurutani, Pitch angle diffusion of energetic particles by large amplitude MHD waves, *Proc. 28th Int'l Cosmic Ray Conf.*, pp. 3709-3712, 2003.01. |

115. |
Pitch angle diffusion of charged particles by large amplitude MHD turbulence. |

116. |
Phase correlation among MHD waves. |

117. |
Non-classical diffusion of energetic particles in a two-dimensional magnetic field turbulence. |

118. |
Shuichi Matsukiyo, Tohru Hada, Nonlinear evolution of electromagnetic waves driven by the relativistic ring distribution, *Physics of Plasmas*, 10.1063/1.1431593, 9, 2, 649, 2002.02. |

119. |
B. T. Tsurutani, L. D. Zhang, G. L. Mason, G. S. Lakhina, T. Hada, J. K. Arballo, R. D. Zwickl, Particle transport in He-3-rich events: wave-particle interactions and particle anisotropy measurements, *Annales Geophys.*, 20, 4, 427-444, vol. 20, no.4, pp.427-444, 2002.01. |

120. |
T. Hada, E. Yamamoto, D. Koga, Phase correlation of MHD waves in the Earth's foreshock, *Rep. Res. Inst. Applied Mech.*, vol. 117, pp.131-135, 2002.01. |

121. |
B. T. Tsurutani, L. D. Zhang, G. L. Mason, G. S. Lakhina, Tohru Hada, J. K. Arballo, R. D. Zwickl, Particle transport in ^{3}He-rich events Wave-particle interactions and particle anisotropy measurements, *Annales Geophysicae*, 20, 4, 427-444, 2002, Energetic particles and MHD waves are studied using simultaneous ISEE-3 data to investigate particle propagation and scattering between the source near the Sun and 1 AU. ^{3}He-rich events are of particular interest because they are typically low intensity "scatter-free" events. The largest solar proton events are of interest because they have been postulated to generate their own waves through beam instabilities. For ^{3}He-rich events, simultaneous interplanetary magnetic spectra are measured. The intensity of the interplanetary "fossil" turbulence through which the particles have traversed is found to be at the "quiet" to "intermediate" level of IMF activity. Pitch angle scattering rates and the corresponding particle mean free paths λ_{W}-P are calculated using the measured wave intensities, polarizations, and k directions. The values of λ_{W}-_{P} are found to be ∼ 5 times less than the value of λ_{He}, the latter derived from He intensity and anisotropy time profiles. It is demonstrated by computer simulation that scattering rates through a 90° pitch angle are lower than that of other pitch angles, and that this is a possible explanation for the discrepancy between the λ_{W}-_{P} and λ_{He} values. At this time the scattering mechanism(s) is unknown. We suggest a means where a direct comparison between the two λ values could be made. Computer simulations indicate that although scattering through 90° is lower, it still occurs. Possibilities are either large pitch angle scattering through resonant interactions, or particle mirroring off of field compression regions. The largest solar proton events are analyzed to investigate the possibilities of local wave generation at 1 AU. In accordance with the results of a previous calculation (Gary et al., 1985) of beam stability, proton beams at 1 AU are found to be marginally stable. No evidence for substantial wave amplitude was found. Locally generated waves, if present, were less than 10^{-3}nT^{2}Hz^{-1} at the leading proton event edge, where dispersion effects (beaming) are the greatest, and at the point of peak proton flux, where the particle energy flux is the greatest.. |

122. |
Bruce T. Tsurutani, John K. Arballo, Carlos Galvan, Liwei Dennis Zhang, Xiao Yan Zhou, Gurbax S. Lakhina, Tohru Hada, Jolene S. Pickett, Donald A. Gurnett, Polar cap boundary layer waves An auroral zone phenomenon, *Journal of Geophysical Research*, 106, A9, 19035-19055, 2001.09, Polar cap boundary layer waves are ELF/VLF electric and magnetic waves detected on field lines just adjacent to the polar cap. Intense waves are present at this location essentially all (96%) of the time. The wave latitude-local time distribution is shown to be the same as that of the Feldstein auroral oval, a distribution centered at ∼75° at local noon and ∼65° at local midnight. The most intense waves are detected coincident with the strongest magnetic field gradients (field-aligned currents). Statistically, the wave intensities are greatest near local noon (10^{-13} mV^{2} m^{-1} at 3 kHz) and midnight and are least near dawn and dusk (∼5 × 10^{-15} mV^{2} m^{-1} at 3 kHz). The noon and midnight wave intensities increase slightly when the interplanetary magnetic field is directed southward. The dawn and dusk waves appear to be controlled by the solar wind speed. Using high-resolution data, specific frequency bands of electromagnetic whistler-mode waves are identified: ∼200 Hz and 1-2 and ∼5 kHz. These may correspond to previously identified "magnetic noise bursts" and "auroral hiss", respectively. Assuming cyclotron resonant interactions, the 1- to 5-kHz auroral hiss is shown to be resonant with ∼50-eV to ∼1.0-keV electrons. Several mechanisms, both resonant (nonlocal) and nonresonant (local), are suggested for the generation of the ∼200-Hz electromagnetic waves. Three types of intense electric signals are present: solitary bipolar pulses (electron holes), waves at ∼4 × 10^{2} to 6 × 10^{3} Hz (lower hybrid waves), and narrowband waves at ∼10 kHz (electrostatic waves near the upper hybrid resonance frequency). Solitary bipolar pulse onset events have been detected for the first time. The bipolar pulses reached 2 mV m^{-1} peak-to-peak amplitudes within 3 ms. An exponential growth rate of 0.72 ms, or 0.25 f_{ce}, was determined. The previously reported "broadband nature" of the polar cap boundary layer (and low-latitude boundary layer) waves is now postulated to be caused by a fast switching between the various electromagnetic and electrostatic modes described above. The polar cap boundary layer waves are most likely a consequence of instabilities associated with auroral zone field-aligned currents carried by 50-eV to 1.0-keV electrons and protons. The currents in turn have been ascribed to be driven by the solar wind-magnetosphere global interaction. One consequence of the presence of the waves at high altitudes is diffusion of magnetosheath plasma into the magnetosphere and magnetospheric plasma out into the magnetosheath (cross-field diffusion, due to parasitic wave-particle interactions). It is speculated that field-aligned currents and similar wave modes will be detected at all planetary magnetospheres.. |

123. |
M. Nambu, B. J. Saikia, T. Hada, Wake potential around a test dust particulate in a magnetized plasma with streaming ions, *J. Phys. Soc. Jpn.*, 10.1143/JPSJ.70.1175, 70, 5, 1175-1177, vol. 70, no. 5, pp.1175-1177, 2001.01. |

124. |
B. T. Tsurutani, J. K. Arballo, C. Galvan, L. D. Zhang, X. Y. Zhou, G. S. Lakhina, T. Hada, J. S. Pickett, D. A. Gurnett, Polar cap boundary layer waves: An auroral zone phenomenon, *J. Geophys. Res.*, 10.1029/2000JA003007, 106, A9, 19035-19055, 2001.01. |

125. |
B. T. Tsurutani, J. K. Arballo, C. Galvan, L. D. Zhang, G. S. Lakhina, T. Hada, J. S. Pickett, D. A. Gurnett, Auroral zone plasma waves detected at polar: PCBL waves, *Adv. Space Res.*, 10.1016/S0273-1177(01)00483-5, 28, 11, 1655-1659, vol. 28, no.11, pp.1655-1659, 2001.01. |

126. |
B. T. Tsurutani, B. Buti, J. K. Arballo, T. Hada, E. J. Smith, A. Balogh, Alfven waves, magnetic decreases, and discontinuities in interplanetary space, *ALFVENIC STRUCTURES: FROM THE SUN TO THE MAGNETOSPHERE*, 10.1016/S0273-1177(01)00507-5, 28, 5, 765-769, vol. 28, no.5, pp.765-9, 2001.01. |

127. |
Nonlinear interaction between a charged particle and an MHD pulse. |

128. |
Parametric instabilities of Alfven waves in a relativistic electron-positron plasma. |

129. |
Y. Kuramitsu, Tohru Hada, Acceleration of charged particles by large amplitude MHD waves Effect of wave spatial correlation, *Geophysical Research Letters*, 10.1029/2000GL003770, 27, 5, 629-632, 2000.03, We discuss energy diffusion and acceleration of charged particles by large amplitude magnetohydrodynamic (MHD) waves by test particle simulations, paying particular attention to the effects of phase correlation of the waves. In quasi-linear theory, the wave phases are assumed to be random, but in reality, interaction between different wave modes may produce phase correlation. When the wave phases are strongly correlated, the waveform appears as spatially localized traveling wave packet. These wave packets can efficiently accelerate charged particles, as they are repeatedly mirror reflected by oppositely propagating wave packets: a process analogous to the Fermi acceleration.. |

130. |
Y. Kuramitsu, T. Hada, Acceleration of charged particles by large amplitude MHD waves: effect of wave spatial correlation, *Geophys. Res. Lett.*, 10.1029/1999GL010726, 27, 5, 629-632, vol. 27, no.5, 2000.01. |

131. |
B. Buti, M. Velli, P. C. Liewer, B. E. Goldstein, T. Hada, Hybrid simulations of collapse of Alfvenic wave packets, *Phys. Plasmas*, 10.1063/1.1289890, 7, 10, 3998-4003, 2000.01. |

132. |
B. T. Tsurutani, L. D. Zhang, G. Mason, G. S. Lakhina, T. Hada, J. K. Arballo, and R. D. Zwickl, Solar energetic 3He mean free paths: comparison between wave-particle and particle anisotropy results, *Acceleration and transport of energetic particles observed in the heliosphere: ACE2000 symposium*, pp. 165-168, 2000.01. |

133. |
Transport of cosmic rays in a turbulent magnetic field. |

134. |
S. Matsukiyo, T. Hada, Long Time Evolution of Electromagnetic Waves Driven by the Relativistic Ring Distribution, *総理工報告*, vol.22, pp.375-384, 2000.01. |

135. |
S. Matsukiyo, T. Hada, M. Nambu, J. Sakai, Comparison between the Landau and cyclotron resonances in the electron beam-plasma interactions, *J. Phys. Soc. Jpn*, 10.1143/JPSJ.68.1049, 68, 3, 1049-1054, vol. 68, no.3, pp. 1049-54, 1999.01. |

136. |
T. Hada, F. Jamitzky, M. Scholer, Consequences of nongyrotropy in magneto-hydrodynamics, *Adv. Space Res.*, 10.1016/S0273-1177(99)00426-3, 24, 1, 67-72, vol. 24, no.1, pp.67-72, 1999.01. |

137. |
V. Krasnoselskikh, T. Hada, B. Lefebvre, Anomalous acceleration/heating of charged particles in a random electric field, *AIP Conference Proceedings*, no. 471, pp. 377-80, 1999.01. |

138. |
On the anomalous acceleration/heating of particles by a random electric field. |

139. |
Yasumasa Ookouchi, Tohru Hada, Chaotic Convection in a Simple System Modified by Differential Heating, *Journal of the Physical Society of Japan*, 10.1143/JPSJ.66.369, 66, 2, 369-378, 1997.01, In this report, a modified Lorenz system is introduced for describing convective motion heated from below with a sinusoidal differential heating. The system includes two additional terms which intensifies the vorticity and stabilizes the temperature field. These two terms bring a new complex behavior. For a large horizontal temperature difference, the onset of chaotic convection is suppressed by the temperature difference and the marginal Rayleigh number is proportional to h^{2}, where h is the horizontal difference in Rayleigh numbers. However, chaotic convection appears in a broad range of Rayleigh numbers.. |

140. |
Y. Saitou, T. Honzawa, Tohru Hada, Observation of spontaneously excited chaos-like ion plasma oscillations, *Physics of Plasmas*, 10.1063/1.871060, 2, 10, 3605-3608, 1995, An oscillation which behaves quite similarly to chaos under some conditions is observed to exist among ion plasma oscillations spontaneously excited in an ion beam-plasma system. There are two different states of the system, the "silent" and "chaotic" states, sensitively depending on the value of a direct current (DC) voltage V_{B}, which determines the beam energy and is adopted as a control parameter here. In the chaotic state, a spontaneously excited ion plasma oscillation is observed to become chaotic. Here, the correlation dimension for the oscillation in the chaotic state is calculated to be 1.64±0.22. The result shows that an attractor for the oscillation has a low degree of freedom and a noninteger dimension.. |

141. |
Tohru Hada, Evolutionary conditions in the dissipative MHD system Stability of intermediate MHD shock waves, *Geophysical Research Letters*, 10.1029/94GL02239, 21, 21, 2275-2278, 1994.01, The evolutionary conditions in the dissipative magnetohydrodynamic (MHD) system are discussed, and the results are applied to argue stability of MHD intermediate shock waves. When dissipative wave modes are included, arbitrary perturbations given to the shock can be expressed as a superposition of outgoing wave modes from the shock: thus, intermediate shocks are evolutionary in dissipative MHD. The matching conditions of incoming and outgoing wave modes at the shock give an under‐determined set of equations, which defines a unique solution when the minimum dissipation principle is imposed.. |

142. |
M. Nambu, Tohru Hada, T. Terasawa, K. S. Goswami, S. Bujarbarua, Plasma maser interaction with magnetohydrodynamic wave turbulence, *Physica Scripta*, 10.1088/0031-8949/47/3/012, 47, 3, 419-427, 1993.03, The energy up-conversion from the kinetic Alfven wave turbulence to the ordinary mode radiation through the plasma-maser process is studied. Thegrowth rate of the ordinary mode originates from two mode-mode coupling terms, viz: The direct and polarization terms. In contrast to the previous electrostatic wave case, both contributions give large growth rate forthe ordinary mode radiation. The results have potential importance tointerpret numerous astrophysical radio phenomena, because the magnetohydrodynamic (MHD) waves contain the dominant turbulent fluctuationsin astrophysical plasmas.. |

143. |
Mitsuhiro Nambu, Tohru Hada, Conservation relations and violation of the Manley-Rowe relation for plasma-maser instability, *Physics of Fluids B*, 5, 3, 742-751, 1993, The total momentum and energy conservation relations between particle kinetic energy and wave energy is satisfied for the plasma-maser instability. The Manley-Rowe relation for plasma waves is violated and as a result an efficient energy up-conversion from the low-frequency mode to the high-frequency mode is possible even for a normal unreversed electron population in plasma turbulence. The entropy production rate for plasma turbulence with plasma-maser instability is estimated. The plasma-maser instability always coexists with the quasilinear interaction, thus it has a potential importance to interpret numerous experiments in fusion and astrophysical plasmas.. |

144. |
Tohru Hada, Evolution of large amplitude Alfvén waves in the solar wind with β∼1, *Geophysical Research Letters*, 10.1029/93GL02704, 20, 22, 2415-2418, 1993, A new set of equations is obtained which describes evolution of finite amplitude, dispersive, elliptically polarized quasi‐parallel Alfvén waves, when the plasma and the wave amplitude satisfy the condition, |1‐C_{S} ^{2}/C_{A} ^{2}| < δB/B_{0}, where C_{A} and C_{s} are the Alfvén and the sound speed, respectively, and δB/B_{0} is the Alfvén wave amplitude normalized to the background magnetic field. When this condition is satisfied, the sound wave as well as the right‐ and left‐hand polarized Alfvén waves are nearly all degenerated. The solar wind plasma is a typical medium for the obtained set of equations to apply, since the plasma β is high, and the solar wind Alfvén waves have large amplitude. Modulational instability of a circularly polarized parallel Alfvén wave is discussed.. |

145. |
Tohru Hada, R. L. Hamilton, C. F. Kennel, The soliton transform and a possible application to nonlinear Alfvén waves in space, *Geophysical Research Letters*, 10.1029/93GL00073, 20, 9, 779-782, 1993, We apply the inverse scattering transform (IST) based upon the Derivative Nonlinear Schrödinger (DNLS) equation to a complex time series of nonlinear Alfvén wave data generated by numerical simulation. The IST describes the long‐time evolution of quasi‐parallel Alfvén waves more efficiently than the Fourier transform, which is adapted to linear, not nonlinear, problems. When we add dissipation, so the conditions for the validity of the DNLS are not strictly satisfied, the IST continues to provide a compact description of the wave‐field in terms of a small number of decaying envelope solitons. Since large amplitude Alfvén waves and other nonlinear waves play essential roles in various space environments—the solar wind is one obvious example—we suggest that it may be of interest to investigate how inverse scattering transforms can be developed into practical tools for the analysis of space data.. |

146. |
Tohru Hada, M. Nambu, On stability of strongly nonlinear plasma oscillations, *Physics of Fluids B*, 10.1063/1.860219, 4, 3, 757-759, 1992.01, The modulational instability of finite-amplitude, longitudinal, nonlinear plasma oscillations in a cold plasma is discussed. Stable and unstable regimes appear alternatively as the wave nonlinear parameter ε varies. A possible laboratory experiment that may confirm this result is suggested.. |

147. |
K. K. Sarma, S. N. Sarma, M. Nambu, Tohru Hada, Electromagnetic emission due to nonlinear forces, *Physical Review A - Atomic, Molecular, and Optical Physics*, 10.1103/PhysRevA.43.5555, 43, 10, 5555-5559, 1991.01, A theory of emission of electromagnetic radiation in a plasma with Langmuir turbulence through the plasma-maser interaction owing to a dissipative nonlinear force is presented. The nonlinear force that arises as a result of the resonant interaction between electrons and modulated fields is shown to drive the instability. The growth rate of the electromagnetic emission is obtained, and the results are discussed.. |

148. |
Mitsuhiro Nambu, Tohru Hada, S. N. Sarma, S. Bujarbarua, Dissipative Structure in Plasma Turbulence, *Journal of the Physical Society of Japan*, 10.1143/JPSJ.60.3004, 60, 9, 3004-3014, 1991, A new enhanced radiation process from plasma turbulence (plasma-maser) is interpreted as “dissipative structure” in plasma turbulence. The plasma-maser process is effective in an open plasma system where some of the input energy is dissipated as anomalous radiation. The validity of the linear response theory which neglects the ensemble averaged second order electric field is given under the random phase approximation. The ordinary mode growth rate in the presence of the enhanced stationary Langmuir turbulence is obtained and the results have potential importance to clarify the mechanism of the anomalous radiation in plasma astrophysics.. |

149. |
C. C. Wu, Tohru Hada, Formation of intermediate shocks in both two-fluid and hybrid models, *Journal of Geophysical Research*, 96, 3, 3769-3778, 1991, Intermediate shocks are studied in a two-fluid model that includes finite ion inertia dispersion and in a hybrid model in which the full ion dynamics is retained while the electrons are treated as a massless fluid. We show that in both models intermediate shocks can be formed through wave steepening, meaning that they are stable and possess shock structures.. |

150. |
C. C. Wu, Tohru Hada, On rotational discontinuities in both two-fluid and hybrid models, *Journal of Geophysical Research*, 96, 3, 3755-3767, 1991, Rotational discontinuities are studied in a two-fluid model that includes finite ion inertia dispersion and in a hybrid model in which the full ion dynamics is retained while the electrons are treated as a massless fluid. We show that as in previous dissipative MHD studies, a rotational discontinuity is unstable in both models and evolves to a 2 → 3 intermediate shock, a slow rarefaction wave, and other waves. (However, due to the limitation in computational resources, the hybrid calculations are limited to low-to-medium ion beta.) In addition, we show that the so-called Walén relation, which holds exactly for rotational discontinuities, can also be well satisfied by tran-Alfvénic intermediate shocks. Thus intermediate shocks can be candidates for those observed structures that satisfy the Walén relation.. |

151. |
Tohru Hada, C. F. Kennel, B. Buti, E. Mjølhus, Chaos in driven Alfvén systems, *Physics of Fluids B*, 10.1063/1.859383, 2, 11, 2581-2590, 1990.01, The chaos in a one-dimensional system, which would be nonlinear stationary Alfvén waves in the absence of an external driver, is characterized. The evolution equations are numerically integrated for the transverse wave magnetic field amplitude and phase using the derivative nonlinear Schrödinger equation (DNLS), including resistive wave damping and a long-wavelength monochromatic, circularly polarized driver. A Poincaré map analysis shows that, for the nondissipative (Hamiltonian) case, the solutions near the phase space (soliton) separatrices of this system become chaotic as the driver amplitude increases, and "strong" chaos appears when the driver amplitude is large. The dissipative system exhibits a wealth of dynamical behavior, including quasiperiodic orbits, period-doubling bifurcations leading to chaos, sudden transitions to chaos, and several types of strange attractors.. |

152. |
E. Mjølhus, Tohru Hada, Oblique stability of circularly polarized MHD waves, *Journal of Plasma Physics*, 10.1017/S002237780001477X, 43, 2, 257-268, 1990.01, The stability of finite-amplitude weakly dispersive circularly polarized MHD wave trains with respect to oblique modulations is investigated. The mathematical model is a multi-dimensional extension of the DNLS equation. We have found that the right-hand-polarized wave, which is stable with respect to parallel modulations, is unstable with respect to certain oblique modulations for most primary wavenumbers.. |

153. |
Tohru Hada, C. F. Kennel, B. Buti, Stationary nonlinear Alfvén waves and solitons, *Journal of Geophysical Research*, 65-77, 1989, Stationary solutions of the derivative nonlinear Schroedinger equation are discussed and classified by using a pseudopotential formulation. The solutions consist of a rich family of nonlinear Alfvén waves and solitons with parallel and oblique propagation directions. Expressions for the envelope and the phase of nonlinear waves with periodic envelope modulation, and “hyperbolic” and “algebraic” solitons are given. We evaluate the propagation angle for the slightly modulated elliptic, periodic waves and for oblique solitons. Also, we present periodic stationary waves which may arise in numerical simulations using periodic boundary conditions. The parallel and oblique stationary solutions discussed here can serve as a starting point for studies of modulational and decay instabilities and for a stability analysis of the solitons.. |

154. |
C. F. Kennel, B. Buti, Tohru Hada, R. Pellat, Nonlinear, dispersive, elliptically polarized Alfvén waves, *Physics of Fluids B*, 31, 1949-1961, 1988.06, The derivative nonlinear Schrödinger (DNLS) equation is derived by an efficient means that employs Lagrangian variables. An expression for the stationary wave solutions of the DNLS that contains vanishing and nonvanishing and modulated and nonmodulated boundary conditions as subcases is then obtained. The solitary wave solutions for elliptically polarized quasiparallel Alfvén waves in the magnetohydrodynamic limit (nonvanishing, unmodulated boundary conditions) are obtained. These converge to the Korteweg–de Vries and the modified Korteweg–de Vries solitons obtained previously for oblique propagation, but are more general. It is shown there are no envelope solitary waves if the point at infinity is unstable to the modulational instability. The periodic solutions of the DNLS are charcterized.. |

155. |
Shinobu Machida, C. K. Goertz, Tohru Hada, The electromagnetic ion cyclotron instability in the Io torus, *Journal of Geophysical Research*, 93, 7, 7545-7550, 1988, The electromagnetic ion cyclotron waves which are expected to exist in the Jovian magnetosphere are investigated. The temperature anisotropy generated by the inward radial diffusion of hot ions gives rise to an instability of L mode waves in the off-equatorial region of the Io torus. The resulting pitch angle scattering has been suggested as the cause for the precipitation of ions into the loss cone and auroral excitation. The linear wave dispersion is first examined, and the nonlinear wave amplitude for the saturated state is studied. Two estimates of the wave saturation level are checked by performing an electromagnetic hybrid simulation. Estimated nonlinear saturation amplitudes are compared with those resulting from linear amplification in a finite length. The result shows that the waves in the Jovian magnetosphere produced by the hot protons are mostly in a linear regime.. |

156. |
Tohru Hada, C. F. Kennel, T. Terasawa, Excitation of compressional waves and the formation of shocklets in the earth's foreshock, *Journal of Geophysical Research*, 92, 5, 4423-4435, 1987, Large-amplitude waves with typical frequencies of 0.01-0.05 Hz are often observed in the foreshocks of earth and other planets. Large-amplitude waves in the earth's foreshock are sometimes (but not always) observed in a highly time-developed form, either as steepened pulses or as discrete oscillatory wave packets of finite length. This implies that nonlinearities are strong enough to modify their waveforms before the solar wind carries them out the foreshock. The instabilities and steepening of upstream waves in the earth's foreshock caused by backstreaming ions are discussed in the first part of the paper. For typical foreshock “diffuse” ion distributions, right and left-hand polarized (RHP and LHP) waves propagating parallel to the local magnetic field are preferentially excited. Such noncompressional waves neither steepen nor grow fast enough to account for the amplitude polarizations and waveforms observed in the diffuse ion foreshock. Oblique waves develop a density compression and their magnetic field polarization is elliptical. Although these characteristics match the observations of the steepened waves in the diffuse ion zone, the growth rates of those waves oblique enough to steepen are too small to account for the observed amplitudes. On the other hand, the parallel propagating waves excited by the “reflected” ion distribution at the leading edge of the foreshock do grow fast enough, but do not steepen. We suggest that parallel propagating waves grow to finite amplitude in the “reflected” and “intermediate” ion zones of the earth's foreshock and refract as they are carried by the solar wind into the “diffuse” ion region, so that they become increasingly oblique and compressional. The more compressional they become, the more rapidly they steepen. Some steepen to the point where finite ion inertia dispersion wave creates a nonlinear wave train—a shocklet. Because wave refraction is less important in the very large foreshocks of interplanetary shocks, it is less likely that oblique, compressive, steepened waves will be generated in them, in agreement with observation. In the second part of this paper, we will simulate the time evolution of oblique low-frequency compressive waves using a one-dimensional hybrid code in which main ions are treated as superparticles, diffuse ions as a double-adiabatic fluid, and electrons as an isothermal fluid. Unlike conventional hybrid codes, parallel and perpendicular pressures of fluids are treated independently. This is necessary in order to well describe the compressional properties of obliquely propagating right-hand polarized waves in a high β plasma. We initialize the simulations with an oblique sinusoidal low-frequency wave of finite amplitude. Nonlinear steepening, formation of discrete dispersive wave packets, and subsequent ion cyclotron damping of the wave packets are found to occur.. |

157. |
T. Terasawa, M. Hoshino, J-I. Sakai, Tohru Hada, Decay instability of finite-amplitude circularly polarized Alfven waves - A numerical simulation of stimulated Brillouin scattering, *Journal of Geophysical Research*, 91, A4, 4171-4187, 1986, By means of a numerical simulation, nonlinear evolution of large amplitude dispersive Alfven waves is studied. An energy transfer from the parent wave to two daughter Alfven-like waves and a soundlike wave is observed (a stimulated Brillouin scattering process). The observed growth rates and propagation characteristics of these daughter waves agree with the analytical results, which we obtain by extending the previous treatments by Goldstein, Derby, Sakai, and Sonnerup. Ions are first trapped by the electrostatic potential of the daughter soundlike waves. Along with the eventual decay (ion Landau damping) of the soundlike waves, ions are phase-mixed and left heated in the parallel direction. The increased parallel energy of ions is transferred to the perpendicular thermal energy through the nonresonant scattering process in the colliding Alfven waves (parent and daughter waves). We further observe that the daughter Alfven waves, which still have a large amplitude, are also unstable for further decay, and that the wave energy is continuously transferred to the longer wavelength regime (inverse cascading process).. |

158. |
Tohru Hada, C. F. Kennel, NONLINEAR EVOLUTION OF SLOW WAVES IN THE SOLAR WIND., *Journal of Geophysical Research*, 10.1029/JA090iA01p00531, 90, A1, 531-535, 1985.01, It is shown by numerical simulation using a hybrid code that comparison of the nonlinear steepening rate, calculated from fluid theory, with the linear collisionless damping rate, defines reasonably well the parameters from which fast and slow MHD waves should steepen. The results indicate that, whereas fast modes should ordinarly steepen, steepened slow waves should occur rarely in the solar wind near 1 AU.. |

159. |
Atsuhiro Nishida, Tohru Hada, K. A. Anderson, R. R. Anderson, S. J. Bame, E. W. Jr. Hones, Broadband electrostatic noise in the magnetotail - Its relation to plasma sheet dynamics,, *Journal of Geophysical Research*, 90, 5, 4453-4460, 1985, Intense broadband electrostatic noise is often observed in the magnetotail when the fast tailward flow and the southward polarity of the magnetic field indicate the progress of reconnection. We compare features of the noise with simultaneous observations of the magnetic field, plasma and energetic electrons. The noise intensity seems to maximize when the plasma density minimizes and the energetic electron flux rises in a spikelike fasion, appreciably later than the onset of the fast tailward flow associated with the southward magnetic polarity. Spectral characteristics of the noise suggest that in its high frequency math formula part at least the noise does not belong to normal modes of plasma waves. Several possibilities are considered for what this noise might be, including quasi-thermal noise in the non-Maxwellian plasma, artificial noise generated by spacecraft interaction with the medium, or electrostatic noise with wavelengths less than a Debye length.. |

160. |
Tohru Hada, Atsuhiro Nishida, T. Terasawa, E. W. Hones, Bi-directional electron pitch angle anisotropy in the plasma sheet, *Journal of Geophysical Research*, 86, 11211-11224, 1981, Analysis of low-energy particle measurement on Imp 6 satellite have revealed the occurrence of bi-directional electron pitch angle anisotropy (enhanced flux in field-aligned directions) in the magnetotail at the energy range of several hundreds to several keV. The bi-directional anisotropy was observed most commonly near the neutral sheet, with a parallel and perpendicular temperature ratio of 2–3, and they appeared also just inside of the magnetopause and in the boundary layer. The anisotropy of this extent was not an unusual phenomenon in the plasma sheet; in about 10% of the total of ∼200-hour interval that we examined electrons had bi-directional anisotropy. On the other hand, more sharply field-aligned electron flux enhancements, which cannot be represented by a Maxwellian distribution, are sometimes observed at radial distances of ∼10 RE, near the inner edge of the plasma sheet. The small pitch angle (less than ∼10°) observed in such cases suggests coupling of the enhanced field-aligned component with the ionosphere. In this paper we describe the observed characteristics of these anisotropic distributions and attempt to explain their formation by Fermi acceleration process in the plasma sheet. Owing to this process, electrons are more accelerated in parallel than perpendicular directions to the magnetic field as they traverse the neutral sheet. The effect of static electric field along the field line caused by the difference in pitch angle anisotropy of protons and electrons is also discussed.. |