Kyushu University Academic Staff Educational and Research Activities Database
Researcher information (To researchers) Need Help? How to update
Shuichi Matsukiyo Last modified date:2021.06.30



Graduate School
Undergraduate School
Other Organization


E-Mail *Since the e-mail address is not displayed in Internet Explorer, please use another web browser:Google Chrome, safari.
Homepage
https://kyushu-u.pure.elsevier.com/en/persons/shuichi-matsukiyo
 Reseacher Profiling Tool Kyushu University Pure
http://www.esst.kyushu-u.ac.jp/~space/
Academic Degree
PhD in science
Country of degree conferring institution (Overseas)
No
Field of Specialization
Space Environmental Fluid Dynamics, space plasma physics
ORCID(Open Researcher and Contributor ID)
https://orcid.org/0000-0002-4784-0301
Total Priod of education and research career in the foreign country
02years01months
Outline Activities
High energy space and astrophysical plasma phenomena like particle acceleration, collisionless shock wave, and nonlinear waves, etc., are investigated by means of theory, numerical simulation, and high power laser experiment.
Research Topics:
Theory and simulation on particle acceleration, energy dissipation at collisionless shocks
Theory and simulation on the structures of heliospheric boundaries and the associated particle acceleration processes
Theory and simulation on cosmic ray invasion and transport processes into the heliosphere
Theory and simulation on wave generation and particle acceleration in a relativistic plasma
High power laser experiment on the formation of collisionless shocks
Education:
 Research guidance to graduate and undergraduate students
Lectures in the graduate and the under graduate schools
Research
Research Interests
  • Study on boundary structure of the heliosphere and cosmic ray invasion and transport through it
    keyword : heliosphere, cosmic rays, termination shock, heliopause
    2017.04.
  • Structure of the Earth's foreshock and particle acceleration
    keyword : Earth's bow shock, foreshock, particle acceleration
    2015.09.
  • Experimental Study on Collisionless Shock
    keyword : laser experiment, collisionless shock
    2013.04.
  • Structure of the heliospheric termination shock and particle acceleration
    keyword : termination shock, particle acceleration, pickup ions
    2007.05.
  • Nonlinear wave generation and particle acceleration in a multi-ion-species plasma in the vicinity of stellar surface
    keyword : particle acceleration, multi-ion-species plasma
    2010.04~2012.03.
  • Physics of collisionless shocks
    keyword : nonstationary shock wave, anomalous dissipation, microinstability, multi-scale physics
    2002.05.
  • Relativistic particle acceleration in space and astrophysical plasmas
    keyword : relativistic plasma, high energy particle acceleration, cosmic ray
    2005.01.
  • Large amplitude wave-wave and wave-particle interactions in space and astrophysical plasmas
    keyword : large amplitude wave, wave-wave interaction, wave-particle interaction
    1999.01.
Current and Past Project
  • The mechanism of electron acceleration in collisionless shock is investigated by using high accuracy spacecraft data and numerical simulation.
  • Experimental study of astrophysics using high power laser
  • Recent multi-spacecraft observations indicate that in Earth's foreshock particle acceleration occurs more efficiently than previously thought. In the foreshock field aligned beam (FAB), which is the high bulk velocity ion beam flowing away from the Earth's bow shock, is often observed. We propose a model that the waves generated by the FAB efficiently scatter high energy particles so that increase the acceleration efficiency. The model is verified by using numerical simulations and spacecraft data anayses.
  • Collisionless shocks are ubiquitous in various astrophysical, heliospheric (or solar-terrestrial), and even laboratory phenomena. The aim of this team is to formulate a common understanding regarding the latest knowledge about the initial stage of the particle acceleration (or injection) process at collisionless shocks.
    Recent gamma-ray and X-ray observations of supernova remnants have provided us with the detailed spatial and spectral structure of high-energy particles accelerated at astrophysical shocks, enabling us to discuss particle acceleration processes there. In-situ multi-spacecraft observations in the heliosphere have shown the spatio-temporal structures of shock transition region as well as the local distribution functions of thermal and non-thermal particles. In addition, laboratory astrophysics is now developing and collisionless shocks have come to be successfully reproduced in the laboratory.
    The injection problem in the diffusive shock acceleration scenario is one of the important outstanding issues. In order to understand the injection mechanism(s) at collisionless shocks, we gather our knowledge of the latest observations, simulations, and theory, not only on astrophysical and heliospheric shocks but also on laboratory shocks. It is time now for researchers in different fields to sit together and discuss current status, latest achievements and issues, in each field.
  • micro- to meso-scale structures of the termination shock and the accompanied particle acceleration
  • It is known that a high Mach number collisionless shock is often self-reforming, i.e., the shock front is cyclically formed and destroyed even though the upstream plasma parameters are steady. The self-reformation was originally found in numerical simulation studies, while its observational proof has not been established. In this study the basic features of the self-reformation is revealed by using numerical simulations. In particular we focus the phenomenon called reflected electron burst accompanied by the self-reformation and discuss how it transfers the characteristics of the self-reformation to a remote upstream region.
  • Particle simulations on nonstationary collisionless shocks
  • Microinstabilities as dissipation mechanisms in high Mach number collisionless shocks
Academic Activities
Reports
1. Local interactions between collisionless shock and plasma: Waves, multi-scale physics, particle acceleration/heating.
2. Shuichi Matsukiyo, Youichi Sakawa, Yasuhiro Kuramitsu, Taichi Morita, KENTARO TOMITA, Toseo Moritaka, Hideaki Takabe, Tohru Hada, Ryo Yamazaki, Taichi Ishikawa, Yuta Yamaura, Takayoshi Sano, Naohumi Ohnishi, Hitoki Yoneda, Nigel Woolsey, Robert Crowston, Gianluca Gregori, Michel Koenig, Yutong Li, Experiment of a spherical shock: Effect of the orientation of magnetic field on shock structure and particle acceleration
, 2014.03.
3. Shuichi Matsukiyo, Yasuhiro Kuramitsu, Youichi Sakawa, Taichi Morita, KENTARO TOMITA, Toseo Moritaka, Hideaki Takabe, Tohru Hada, Theoretical study on unmagnetized shocks in counter streaming plasmas, 2014.03.
4. Shuichi Matsukiyo, Yasuhiro Kuramitsu, Youichi Sakawa, Taichi Morita, KENTARO TOMITA, Toseo Moritaka, Hideaki Takabe, Tohru Hada, Full particle-in-cell simulations on the formation of electrostatic shock in a counter streaming plasma, 2013.03.
5. Roles of pickup ions in a collisionless shock: Parameter survey.
6. Roles of pickup ions in a collisionless shock.
7. Particle simulations on nonstationary collisionless shocks.
8. Particle simulations on nonstationary collisionless shocks.
9. Electron heating associated with microinstabilities in high Mach number shocks.
10. Numerical simulation on particle acceleration/heating in high Mach number shocks.
11. Simulation studies on acceleration/heating processes of charged particles in the vicinity of collisionless shock waves.
12. Wave-particle interactions in the vicinity of collisionless shocks in space plasmas.
13. Wave-particle interactions in a transition region of a collisionless shock.
Papers
1. Matsukiyo, S., Parametric instabilities in a two ion species plasma as a driver of super Alfvenic waves, Journal of Physics: Conference Series, 10.1088/1742-6596/1620/1/012013, 1620, 012013(1)-012013(12), 2020.09, [URL].
2. Matsukiyo, S.; Noumi, T.; Zank, G. P.; Washimi, H.; Hada, T., PIC Simulation of a Shock Tube: Implications for Wave Transmission in the Heliospheric Boundary Region, The Astrophysical Journal, 10.3847/1538-4357/ab54c9, 888, 1, 11(1)-11(9), 2020.01, [URL], A shock tube problem is solved numerically by using one-dimensional full particle-in-cell simulations under the condition that a relatively tenuous and weakly magnetized plasma is continuously pushed by a relatively dense and strongly magnetized plasma having supersonic relative velocity. A forward and a reverse shock and a contact discontinuity are self-consistently reproduced. The spatial width of the contact discontinuity increases as the angle between the discontinuity normal and ambient magnetic field decreases. The inner structure of the discontinuity shows different profiles between magnetic field and plasma density, or pressure, which is caused by a non-MHD effect of the local plasma. The region between the two shocks is turbulent. The fluctuations in the relatively dense plasma are compressible and propagating away from the contact discontinuity, although the fluctuations in the relatively tenuous plasma contain both compressible and incompressible components. The source of the compressible fluctuations in the relatively dense plasma is in the relatively tenuous plasma. Only compressible fast mode fluctuations generated in the relatively tenuous plasma are transmitted through the contact discontinuity and propagate in the relatively dense plasma. These fast mode fluctuations are steepened when passing the contact discontinuity. This wave steepening and probably other effects may cause the broadening of the wave spectrum in the very local interstellar medium plasma. The results are discussed in the context of the heliospheric boundary region or heliopause..
3. Matsukiyo, S.; Akamizu, T.; Hada, T., Heavy Ion Acceleration by Super-Alfvénic Waves, The Astrophysical Journal Letters, 10.3847/2041-8213/ab58cf, 887, 1, L2(1)-L2(4), 2019.12, [URL], A generation mechanism of super-Alfvénic (SPA) waves in multi-ion species plasma is proposed, and the associated heavy ion acceleration process is discussed. The SPA waves are thought to play important roles in particle acceleration since they have large wave electric fields because of their high phase velocity. It is demonstrated by using full particle-in-cell simulations that large amplitude proton cyclotron waves, excited due to proton temperature anisotropy, nonlinearly destabilize SPA waves through parametric decay instability in a three-component plasma composed of electrons, protons, and α particles. At the same time, α cyclotron waves get excited via another decay instability. A pre-accelerated α particle resonates simultaneously with the two daughter waves, the SPA waves and the α cyclotron waves, and it is further accelerated perpendicular to the ambient magnetic field. The process may work in astrophysical environments where a sufficiently large temperature anisotropy of lower mass ions occurs..
4. Shuichi Matsukiyo, 蔵満康浩, KENTARO TOMITA, Collective scattering of an incident monochromatic circularly polarized wave in an unmagnetized non-equilibrium plasma, Journal of Physics: Conference Series, 10.1088/1742-6596/688/1/012062, 688, 012062(1)-012062(4), Vol.688, 012062, 2016.04, [URL].
5. Shuichi Matsukiyo, Yosuke Matsumoto, Electron Acceleration at a High Beta and Low Mach Number Rippled Shock, Journal of Physics: Conference Series, 10.1088/1742-6596/642/1/012017, 642, 012017(1)-012017(7), Vol.642, 012017, 2015.09, [URL].
6. Shuichi Matsukiyo, Manfred Scholer, Simulations of pickup ion mediated quasi-perpendicular shocks: Implications for the heliospheric termination shock, Journal of Geophysical Research, 10.1002/2013JA019654, 119, 2014.04.
7. S. Matsukiyo, M. Scholer, Dynamics of energetic electrons in nonstationary quasi-perpendicular shocks, Journal of Geophysical Research, 10.1029/2012JA017986, 117, A11, A11105, vol.117, A11, A11105, 2012.11, [URL].
8. Shuichi Matsukiyo, Yutaka Ohira, Ryo Yamazaki, Takayuki Umeda, Relativistic Electron Shock Drift Acceleration in Low Mach Number Galaxy Cluster Shocks, Astrophysical Journal, 10.1088/0004-637X/742/1/47, 742, Issue 1, article id. 47, vol.742, article id. 47, 2011.11, [URL].
9. S. Matsukiyo, M. Scholer, Microstructure of the heliospheric termination shock: Full particle electrodynamic simulations, Journal of Geophysical Research, 10.1029/2011JA016563, 116, A8, A08106, vol.116, A8, A08106, 2011.08, [URL].
10. Shuichi Matsukiyo, Mach number dependence of electron heating in high Mach number quasiperpendicular shocks, Physics of Plasmas, 10.1063/1.3372137, 17, 4, 042901, Vol.17, Issue 4, pp.042901, 2010.04, [URL].
11. Shuichi Matsukiyo, Tohru Hada, Relativisitic particle acceleration in developing Alfven turbulence, Astrophysical Journal, 10.1088/0004-637X/692/2/1004, 692, Issue 2, 1004-1012, vol.692, pp.1004-1012, 2009.02, [URL].
12. Shuichi Matsukiyo, Manfred Scholer, David Burgess, Pickup protons at quasi-perpendicular shocks: full particle electrodynamic simulations, Annales Geophysicae, 25, Issue 1, 283-291, vol.25, Issue 1, pp.283-291, 2007.01, [URL].
13. Shuichi Matsukiyo, Manfred Scholer, On reformation of quasi-perpendicular collisionless shocks, Advances in Space Research, 10.1016/j.asr.2004.08.012, 38, Issue 1, 57-63, vol. 38, Issue 1, pp.57-63, 2006.09, [URL].
14. Shuichi Matsukiyo, Manfred Scholer, On microinstabilities in the foot of high Mach number perpendicular shocks, Journal of Geophysical Research, 10.1029/2005JA011409, 111, Issue A6, CiteID A06104, vol. 111, Issue A6, CiteID A06104, DOI 10.1029/2005JA011409, 2006.06, [URL].
15. Shuichi Matsukiyo, Rudolf Treumann, Manfred Scholer, Coherent waveforms in the auroral upward current region, Journal of Geophysical Research, 10.1029/2004JA010477, 109, Issue A6, CiteID A06212, Volume 109, Issue A6, CiteID A06212, 2004.06, [URL].
16. Shuichi Matsukiyo, Manfred Scholer, Modified two-stream instability in the foot of high Mach number quasi-perpendicular shocks, Journal of Geophysical Research, 10.1029/2003JA010080, 108, Issue A12, SMP 19-1, Volume 108, Issue A12, pp. SMP 19-1, CiteID 1459, DOI 10.1029/2003JA010080, 2003.12, [URL].
17. Shuichi Matsukiyo, Tohru Hada, Parametric instabilities of circularly polarized Alfvén waves in a relativistic electron-positron plasma, Physical Review E,, 10.1103/PhysRevE.67.046406, 67, Issue 4, id. 046406, vol. 67, Issue 4, id. 046406, 2003.04, [URL].
18. Shuichi Matsukiyo, Tohru Hada, Nonlinear evolution of electromagnetic waves driven by the relativistic ring distribution, Physics of Plasmas, 10.1063/1.1431593, 9, Issue 2, 649-661, Volume 9, Issue 2, February 2002, pp.649-661, 2002.02, [URL].
19. Shuichi Matsukiyo, Tohru Hada, Mitsuhiro Nambu, Jun-Ichi Sakai, Comparison between the Landau and Cyclotron Resonances in the Electron Beam-Plasma Interactions, Journal of Physical Society of Japan, 10.1143/JPSJ.68.1049, 68, Issue 3, 1049-1054, Vol.68, Issue 3, pp.1049-1054, 1999.03, [URL].
Presentations
1. Shuichi Matsukiyo, Kotaro Yoshida, Haruichi Washimi, Gary P. Zank, Kinetic properties of heliospheric boundary, AGU Fall Meeting 2020, 2020.12, [URL], In the heliospheric boundary region matter and energy are extensively transported and/or converted between the heliosphere and the local interstellar space. This region has been explored in-situ by Voyager spacecraft in this century. Voyager spacecraft revealed a lot of features of the two important discontinuities, termination shock and heliopause, as well as unexpected properties of high energy particles in the boundary region. Some of the features have been still not well understood. We first review our full particle-in-cell simulation studies to discuss kinetic properties of the two discontinuities. Then, we further discuss our recent work on the effect of global structure of the heliosphere in the cosmic ray invasion process into the heliosphere..
2. S. Matsukiyo, K. Yoshida, K. Shimokawa, H. Washimi, G. P. Zank, M. Scholer, T. Hada, Heliospheric boundary: Kinetic structure, cosmic ray property, 4th Asia-Pacific Conference on Plasma Physics, 2020.10, [URL], Heliosphere is a bubble occupied by the solar wind plasma and magnetic field in the local interstellar space. Matter and energy are actively transported and/or converted in the boundary region between the heliosphere and the local interstellar space. This region has been explored in-situ by Voyager spacecraft in this century1-18. Voyager spacecraft revealed a lot of features, some of which have been still unresolved, such as complex structures of two important discontinuities, unexpected properties of high energy particles, etc. In this study we first focus on the kinetic structures of the termination shock and the heliopause. Using particle-in-cell simulation, kinetic structure of the transition region of these discontinuities are investigated. In the termination shock the roles of pickup ions are examined carefully19-22. Kinetic structure of the heliopause influenced by the termination shock is also studied3. In the second part of this study the effect of global structure of the heliosphere in the cosmic ray invasion process is considered. It has been unknown how galactic cosmic rays enter and reach deep inside the heliosphere. To understand the cosmic ray invasion process in the level of particle trajectory, we perform a test particle simulation in the global electromagnetic structure of the heliosphere reproduced by using high resolution 3D MHD simulation. A number of characteristic trajectories of different energy cosmic ray particles are reported..
3. S. Matsukiyo, Kinetic radial structure of heliospheric boundary, 3rd Asia-Pacific Conference on Plasma Physics, 2019.11, [URL], Kinetic radial structure of heliospheric boundary
Abstract: The kinetic structure of the heliospheric boundary region is investigated using one-dimensional full PIC (Particle-In-Cell) simulations. A shock tube problem is numerically solved under the condition that a relatively tenuous and weakly magnetized plasma, mimicking the solar wind (SW) plasma, is continuously pushed by a relatively dense and strongly magnetized plasma, mimicking the interstellar (IS) plasma, having supersonic relative velocity. A forward and a reverse shock, corresponding to the SW termination shock and the IS bow shock, and a contact discontinuity, to the heliopause, are self-consistently reproduced. The spatial width of the heliopause increases as the angle between the discontinuity normal and ambient magnetic field decreases. The inner structure of the heliopause shows different profiles between magnetic field and plasma density, or pressure, which is caused by a non-MHD effect of the local plasma. The region between the two shocks is turbulent. The turbulence in the relatively dense plasma, corresponding to the outer heliosheath, is compressible and propagating away from the heliopause, although the turbulence in the relatively tenuous plasma, corresponding to the inner heliosheath, contains both compressible and incompressible fluctuations. The source of the compressible turbulence in the outer heliosheath is in the inner heliosheath. Only compressible fast mode fluctuations generated in the inner heliosheath are transmitted through the heliopause and propagate in the outer heliosheath. The results are discussed in the context of recent observations by Voyager spacecraft..
4. Shuichi Matsukiyo, Acceleration of relativistic electrons at a high beta shock, 10th Korean Astrophysics Workshop: Astrophysics of high-beta plasma in the ICM, 2019.07, [URL], A high beta shock has not been paid much attention from the aspect of particle acceleration, since it is a relatively weak shock so that its structure is more or less laminar and steady where the activities of waves are generally thought to be low. In space, on the other hand, a number of high beta shocks are observed and some of them indicate the evidence of particle acceleration. We found that relativistic shock drift acceleration followed by reflection efficiently works at such a high beta shock by using one-dimensional full particle-in-cell (PIC) simulation. This mechanism is suppressed, however, when the effect of higher dimension is taken into account due to the rippled structure of shock surface. We further consider the presence of halo electrons which are the non-thermal component often observed also in the solar wind. Then, it is found that the halo electrons are preferentially accelerated and reflected. Its efficiency appears to be increased due to the rippled structure..
5. Shuichi Matsukiyo, Gary P. Zank, Haruichi Washimi, Tohru Hada, Kinetic scale radial structure of the heliopause, 18th Annual International Astrophysics Conference, 2019.02, [URL], The kinetic structure of the heliospheric boundaries is investigated using one-dimensional full PIC (Particle-In-Cell) simulations. Both the termination shock and the heliopause are simultaneously reproduced in the simulation. The spatial scale of the heliopause increases as the angle between the heliopause normal and local magnetic field (referred to as the normal angle, hereafter) becomes increasingly oblique. The total pressure, including the plasma pressure and magnetic pressure, at the heliopause is not constant when the normal angle is oblique in contrast to predictions based on MHD theory. In the oblique case, the solar wind plasma and interstellar plasma are able to inter-penetrate by moving along the local magnetic field. Since their bulk velocities along the magnetic field differ from each other, the distributions overlap in phase space so that the effective local plasma pressure parallel to the magnetic field is enhanced. This results in an increase that resembles a hump in the density and
parallel pressure of the local plasma, which is not seen in magnetic field..
6. S. Matsukiyo, Microstructure of high beta quasi-perpendicular shock and associated electron dynamics, 2nd Asia-Pacific Conference on Plasma Physics, 2018.11, [URL], Electron acceleration in a high beta and low Mach number quasi-perpendicular collisionless shock is investigated by using one- and two-dimensional full particle-in-cell simulations. In contrast to low beta or high Mach number shocks, relativistic shock drift acceleration followed by reflection is observed in one-dimensional simulation. However, the reflection is suppressed due to the effect of shock surface rippling in two-dimensional simulations, while less efficient reflection is confirmed when shock angle is deviated from perpendicular (The shock angle is defined as the angle between shock normal and upstream magnetic field.). Structure of the shock transition region is much more complicated than previously expected, in spite of the high beta and low Mach number situation. Not only ion scale fluctuations, including the ripple, but also electron scale fluctuations are seen. Among these, downstream fluctuations are dominated by electromagnetic ion cyclotron instability and/or mirror instability, electron scale fluctuations in the overshoot (foot) are due to whistler instability (modified two-stream instability). Relative importance of the instabilities changes with the shock angle. We further studied the behavior of halo electrons whose temperature is one order higher than background upstream electrons. By assuming that relative density of the halo electrons is sufficiently low so that their dynamics do not affect the behavior of electromagnetic fields, the halo electrons are treated as test particles. We found that the halo electrons are preferentially reflected after being accelerated through the shock drift mechanism even if the shock surface ripple is present. They are also heated more efficiently than the background electrons..
7. Shuichi Matsukiyo, Tomoki Noumi, Haruichi Washimi, Tohru Hada, Gary P. Zank, Microstructure of heliospheric boundary and implication for the origin of compressible turbulence in VLISM, 17th Annual International Astrophysics Conference, 2018.03, [URL], Microstructure of heliospheric boundary is investigated by using full PIC (Particle-In-Cell) simulations. Both the termination shock and the heliopause are simultaneously reproduced by using the PIC simulation, although system size is very limited and a strong assumption of one-dimensionality is imposed. Spatial scale of the heliopause increases as the angle between the heliopause normal and interstellar magnetic field becomes oblique. The downstream of the termination shock, the region between the termination shock and the heliopause, contains large amplitude magnetic as well as density fluctuations. The VLISM region also contains some fluctuations in magnetic field and density. We investigated the origin and the characteristics of those fluctuations. The density fluctuations show partly positive and partly negative correlations with the magnetic fluctuations in the downstream of the termination shock. The positively correlated fluctuations are produced in the shock front through the self-reformation process, while the negatively correlated ones are generated through mirror instability. On the other hand, the fluctuations in the VLISM show only positive correlation between magnetic and density fluctuations. Further, the fluctuations propagate from the heliopause to the VLISM, which implies that those fluctuations are originated from the heliosphere..
8. Shuichi Matsukiyo, Fumiko Otsuka, PIC simulation of quasi-parallel shock: Foreshock structure, EGU Meeting 2017, 2017.04, [URL], Electromagnetic structure of a quasi-parallel shock is highly complex. From the viewpoint of numerical kinetic simulation, quite large simulation domain is necessary to reproduce a foreshock region where some particles are back streaming almost freely along the ambient magnetic field. This may be a main reason that full particle-in-cell (PIC) simulations of a quasi-parallel shock have been seldom performed, although there are only a few examples.

Here, both ion and electron scale structures of the foreshock in a quasi-parallel shock are investigated by using one-dimensional full PIC simulation with sufficiently large system size (= 2500 ion inertial lengths). The shock parameters are as follows. The Alfven Mach number is 6.6, upstream ion and electron betas are both 0.5, and the shock angle is 20 deg. The ion to electron mass ratio is 64, the ratio of electron plasma to cyclotron frequency is 12.5. Well developed large amplitude MHD waves, evolution of back streaming ion distribution function, electron scale structure grown in the MHD scale structure, and dynamics of high energy particles are discussed..
9. Shuichi Matsukiyo, Roles of microinstabilities in collisionless shocks, 6th East-Asia School and Workshop on Laboratory, Space, Astrophysical Plasmas, 2016.07, [URL], In a collisionless shock microinstabilities play important roles. They heat an incoming plasma to provide necessary dissipation in a transition region. They are sometimes able to directly produce non-thermal particles. Furthermore, they produce a scatterer of the non-thermal particles in the context of diffusive shock acceleration (DSA). We review the above mentioned roles of microinstabilities in some cases of quasi-perpendicular shocks from the viewpoint of full particle-in-cell simulation.
First, we focus on the instabilities generated in the so-called foot region, which is produced by the ions specularly reflected at the shock (ramp). The reflected ions become a beam in terms of the incoming plasma so that some microinstabilities get excited. Depending on the shock parameters a variety of instabilities are generated. Here, we introduce electron thermal Mach number, Mte, defined as the upstream flow velocity normalized to electron thermal velocity, which is proportional to Alfven Mach number divided by the square root of electron beta. When the Mach number is low, Mte ≲ 1, as in the Earth’s bow shock, electron cyclotron-drift instability, and modified two-stream instability are dominantly generated. These instabilities contribute to electron as well as ion heating. For higher Mach numbers, Mte >> 1, Buneman instability gets excited. The resultant large amplitude waves trap some electrons which are accelerated by the convection electric field to non-thermal energy while being trapped.
On the other hand, when Mte < cosBn (B2/B1)1/2, non-negligible amount of electrons are mirror reflected at a shock. The reflected electrons form a foreshock. In the foreshock resonant and non-resonant instabilities are generated. The latter is also called electron firehose instability and efficiently scatter the reflected electrons. The waves play crucial roles in injection of non-thermal electrons into DSA..
10. Shuichi Matsukiyo, PIC Simulation of High Beta and Low Mach Number Astrophysical Shocks: Microstructures and Electron Acceleration, 5th East-Asia School and Workshop on Laboratory Space and Astrophysical plasmas, 2015.08, [URL].
11. Shuichi Matsukiyo, Electron acceleration at a high beta shock, 14th Annual International Astrophysics Conference, 2015.04, [URL].
12. 松清 修一, Collisionless shocks in magnetized and unmagnetized plasmas: PIC simulation and laser experiment, 大阪大学レーザーエネルギー学研究センター日米ワークショップ, 2014.02.
13. Theoretical studies on the production of high Mach number collisionless shocks.
14. 松清 修一, PIC simulations of the termination shock, 8th European Workshop on Collisionless shocks, 2013.06, [URL].
15. 松清 修一, Manfred Scholer, PIC simulations on the termination shock: Microstructure and electron acceleration, 2013 AGU Meeting of Americas, 2013.05, [URL], The ability of the termination shock as a particle accelerator is totally unknown. Voyager data and recent kinetic numerical simulations revealed that the compression ratio of the termination shock is rather low due to the presence of pickup ions, i.e., the termination shock appears to be a weak shock. Nevertheless, two Voyager spacecraft observed not only high energy ions called termination shock particles, which are non-thermal but less energetic compared to the so-called anomalous cosmic rays, but also high energy electrons. In this study we focus especially on microstructure of the termination shock and the associated electron acceleration process by performing one-dimensional full particle-in-cell (PIC) simulations for a variety of parameters. For typical solar wind parameters at the termination shock, a shock potential has no sharp ramp with the spatial scale of the order of electron inertial length which is suitable for the injection of anomalous cosmic ray acceleration. Solar wind ions are not so much heated, which is consistent with Voyager spacecraft data. If a shock angle is close to 90 deg., a shock is almost time stationary or weakly breathing when a relative pickup ion density is 30%, while it becomes non-stationary if the relative pickup ion density is 20%. When the shock angle becomes oblique, a self-reformation occurs due to the interaction of solar wind ions and whistler precursors. Here, the shock angle is defined as the angle between upstream magnetic field and shock normal. For the case with relatively low beta solar wind plasma (electron beta is 0.1 and solar wind ion temperature equals to electron temperature), modified two-stream instability (MTSI) gets excited in the extended foot sustained by reflected pickup ions, and both solar wind electrons and ions are heated. If the solar wind plasma temperature gets five times higher, on the other hand, the MTSI is weakened and the pre-heating of the solar wind plasma in the extended foot is suppressed. Although the electron acceleration rate is not so much dependent on these microstructures, it depends on the shock angle. The shock drift acceleration efficiently occurs for oblique shocks..
16. S. Matsukiyo, M. Scholer, Microstructure of the Termination Shock: Full PIC Simulation, AOGS-AGU(WPGM) Joint Assembly, 2012.08, [URL], Microstructure of the termination shock reproduced by one-dimensional full particle-in-cell (PIC) simulations is investigated. For typical solar wind parameters at the termination shock, a shock potential has no sharp ramp with the spatial scale of the order of electron inertial length which is suitable for the injection of anomalous cosmic ray acceleration. Solar wind ions are not so much heated, which is consistent with Voyager spacecraft data. These features are due to the presence of pickup ions. Furthermore, when a relative pickup ion density is 30%, a shock is time stationary. For the case with low beta (=0.17) solar wind plasma, modified two-stream instability (MTSI) gets excited in the extended foot sustained by reflected pickup ions, and both solar wind electrons and ions are heated. If the solar wind plasma beta gets five times higher (=0.85), on the other hand, the MTSI is weakened and the pre-heating of the solar wind plasma in the extended foot is suppressed. Other parameter dependence of detailed shock structure on relative pickup ion density, Alfven Mach number, ion-to-electron mass ratio, and electron plasma to cyclotron frequency ratio is discussed..
17. Shuichi Matsukiyo, Manfred Scholer, Full Particle Simulation on Microstructure of Heliospheric Termination Shock, 2011 International Space Plasma Symposium (ISPS2011), 2011.08, [URL].
18. Shuichi Matsukiyo, Full Particle-In-Cell Simulation on Collisionless Shocks:Electron and Ion Dynamics in the Transition Region, The 10th International School/Symposium for Space Simulations (ISSS-10), 2011.07, [URL].
19. Shuichi Matsukiyo, Manfred Scholer, Nonthermal electrons produced by supercritical quasi-perpendicular shocks, 2010 International Space Plasma Symposium, 2010.06, [URL].
20. Shuichi Matsukiyo, Electron Heating through microinstabilities in High Mach Number Quasi-Perpendicular Shocks, 5th Korean Astrophysics Workshop on Shock Waves, Turbulence, and Particle Acceleration, 2009.11, [URL].
21. Shuichi Matsukiyo, Manfred Scholer, Electron heating through microinstabilities in high Mach number quasi-perpendicular shocks, 8TH Annual International Astrophysics Conference, 2009.05, [URL].
22. Shuichi Matsukiyo, Relativistic particle acceleration in developing Alfven turbulence, KINETIC MODELING OF ASTROPHYSICAL PLASMAS, 2008.10, [URL].
23. Shuichi Matsukiyo and Tohru Hada, Relativistic particle acceleration in coherent Alfven waves through parametric instabilities, International Workshop on Nonlinear Waves and Turbulence in Space Plasmas (NLW-7), 2008.04.
24. Shuichi Matsukiyo, Tohru Hada, Relativistic particle acceleration by coherent Alfven waves upstream of collisionless shocks, International Workshop on Plasma Shocks and Particle Acceleration, 2008.01.
25. Shuichi Matsukiyo, Manfred Scholer, PIC simulations of quasi-perpendicular shocks: Roles of modified two-stream instability in particle heating, acceleration, and self-reformation processes, AOGS (Asia Oceania Geoscience Society) meeting 2007, 2007.08, [URL].
26. Shuichi Matsukiyo, Manfred Scholer, Roles of Modified Two-Stream Instability in Supercritical Shock Waves, Japan-Korea Mini-Workshop 2007 on Laboratory, Space and Astrophysical Plasmas, 2007.04, [URL].
27. Shuichi Matsukiyo, Manfred Scholer, Shock angle dependence of nonstationary behaviour of quasi-perpendicular shocks, 2007 IRCS Workshop on Shock Formation under Extreme Environments in the Universe, 2007.02.
28. Shuichi Matsukiyo and Manfred Scholer, Energy dissipation through microinstabilties in the foot of high Mach number quasi-perpendicular shocks, The Sixth International Workshop on Nonlinear Waves and Turbulence in Space Plasmas (NLW-6), 2006.10, [URL].
29. Shuichi Matsukiyo, Manfred Scholer, Microinstabilities in collisionless shocks: recent simulation results, URSI (XXVIIIth General Assembly of International Union of Radio Science), 2005.10.
30. Shuichi Matsukiyo, Manfred Scholer, Reformation of quasi-perpendicular shocks with realistic ion to electron mass ratio, COSPAR colloquia : Dynamical Processes in Critical Regions of the Heliosphere, 2004.03.
Membership in Academic Society
  • Asia Oceania Geosciences Society
  • European Geosciences Union
  • Japan Geoscience Union
  • American Geophysical Union
  • Society of Geomagnetism and Earth, Planetary and Space Sciences
Awards
  • Tanakadate Award
  • Obayashi Early Career Scientist Award
Educational
Educational Activities
Research guidance to graduate and undergraduate students
Lectures in the graduate and the under graduate schools