Tohru Hada | Last modified date：2019.07.31 |

Professor /
Department of Enviromental Fluid Science and Technology

Department of Advanced Environmental Science and Engineering

Faculty of Engineering Sciences

Department of Advanced Environmental Science and Engineering

Faculty of Engineering Sciences

Graduate School

Undergraduate School

Other Organization

E-Mail

Phone

092-583-7099

Fax

092-592-8447

Academic Degree

Ph.D.

Country of degree conferring institution (Overseas)

Yes

Field of Specialization

Space Environmental Fluid Dynamics, Space Plasma Physics, Nonlinear waves

Total Priod of education and research career in the foreign country

05years00months

Outline Activities

Theoretical and numerical simulation studies on various phenomena in space and astrophysical plasma environments. Current research topics include:

-Nonlinear waves and turbulence in space plasma

-Structure and stability of collisionless shocks

-Diffusion and acceleration of cosmic rays

-Modeling of new generation electric plasma thrusters

-Nonlinear waves and turbulence in space plasma

-Structure and stability of collisionless shocks

-Diffusion and acceleration of cosmic rays

-Modeling of new generation electric plasma thrusters

Research

**Research Interests**

- The Earth in space environment

keyword : Space weather, space environment

2004.04～2015.03We conduct studies releavant to space weather and sun-earth relationship. . - next generation electric thrusters

keyword : electric thrusters, helicon plasma

2004.04～2015.03Theoreteical/numerical simulation studies on next generation plasma propulsion systems. - Nonlinear waves and turbulence in space plasmas

keyword : nonlinear wave, MHD wave, turbulence, chaos

1981.01～2015.03Study on nonlinear evolution of finite amplitude MHD waves in space/astro-plasma environment. Various parametric instabilities. Origin of phase coherence. Theory, simulation, and data analysis using spacecraft data (obtained by Japanese + EU projects).. - Collisionless shocks in space and astrophysical plasmas

keyword : collisionless shock, shock stability, relativistic shock, Fermi acceleration, intermediate shock

1981.01～2015.03Structure and stability of collisionless shock waves often found in space and astroplasma environment. Stability (discussion on its existence) of intermediate shocks.. - Acceleration and diffusion of cosmic rays

keyword : diffusion, acceleration, cosmic rays, energetic particles, Levy process

1981.01～2015.03Effect of phase coherence of MHD turbulence on particle diffusion. Anomalous (super-/sub-)diffusion and Levy statistics, diffusive shock acceleration of energetic particles (cosmic rays). .

**Current and Past Project**

- Plasma beta is a ratio between the plasma energy density and the magnetic field energy density. Plasma with large value of the beta is often found in space and astrophysical environments, and is also utilized in some of the nuclear fission experiments. On the other hand, there are only a few basic laboratory experimental studies conducted to study properties of the high beta plasma. In this project, we produce the high beta plasma using helicon device, and study various basic topics such as production and confinement efficiencies, physical processes at the null lines and null surfaces, penetration of electromagnetic plasma waves across the null surface, and chaotic orbits and the birth of anomalous resistivity near the cusp field. Numerical simulations are conducted along with corresponding laboratory experimental studies.
- Electric propulsion is a form of spacecraft propulsion that uses electric energy to accelerate ionized gas or plasma propellant. Compared with chemical thrusters, electric thrusters can offer much higher fuel efficiency, so that many attractive future missions can be realized. However, conventional electric thrusters share an intrinsic weak point, namely a finite lifetime due to the erosion of electrodes that are in direct contact with dense plasma. The objective of our project is to develop a completely electrodeless (i.e., no components that exchange particles with the plasma propellant) plasma rocket engine by integrating and advancing our knowledge on electrodeless plasma production and acceleration. In our advanced-concept thruster, a background magnetic field is applied so as to avoid the propellant plasma to make contact with the thruster vessel. An efficient and convenient way to produce plasma in a magnetic field is to utilize the helicon wave. We will examine several different kinds of electrodeless thruster schemes, by laboratory experiments, theoretical modeling, and computer simulations. The ultimate goal is to achieve the exhaust velocity of 40 km/s and the propulsive efficiency of 50 %.
- Space plasma shocks and their associated phenomena are of primary importance in cosmic electrodynamics, due to their ubiquity in heliospheric and astrophysical contexts. They condition plasmas downstream and dramatically energize particles, which, for example, are believed to be the primary source of cosmic rays. The collisionless shocks observed near 1A.U. have provided a natural laboratory well suited for the study of these structures, since Earth's bow shock and traveling interplanetary shocks span a wide range of applicable parameter space. The extensive dataset of space plasma shock encounters collected by satellites within the past four decades has stimulated a tremendous theoretical effort, including an increasing number of sophisticated numerical experiments, in an attempt to understand associated processes. Much particle energization appears to have been explained by diffusive shock acceleration (DSA) models, but these weak turbulence methods are often not valid for the strong turbulence that is observed, and to date do not fully account for energetic particles seen in association with strongly perpendicular shocks (70o < theta_Bn < 90o). In addition, recent detailed examinations of 3- dimensional ion distributions in the foreshock exhibit non-thermal energetic tails that cannot be readily explained by diffusive processes. A similar conclusion is inferred from recent observations of the X-ray luminosity of gamma ray bursts. Coherent non-linear structures such as Short Large-Amplitude Magnetic Structures (SLAMS) are frequently seen in foreshocks upstream of quasi-parallel shocks (theta_Bn < 45o), but should not produce diffusive acceleration. Similarly, the nonlinear cyclic shock-reformation processes expected to occur should likewise alter the diffusive picture. We propose to bring together a diverse team of theorists, simulators and observers from space physics and astrophysics backgrounds to examine in detail the roles of strong turbulence and singular structures on the acceleration of particles near shocks. Observationally, our team will focus on energetic particle distributions produced by shocks and on further elucidating the descriptions of non-thermal particle distributions and the conditions leading to them. Our theorists will focus on recent applications of field theoretical methods to turbulence that hold promise for the study of heliospheric and astrophysical plasmas. Kinetic simulations will focus on modeling the roles of singular/non-linear structures in particle acceleration. We seek support from ISSI to provide opportunities for our multidisciplinary team to meet, discuss recent results and share ideas to guide ongoing work, since this endeavor will require occasional, but intensive, intercomminication. While individual members of our group will write independent papers on their findings, we propose to also jointly author a paper summarizing the progress from the team effort, which we anticipate will have significant impact for future work in space plasma particle acceleration applications.

**Academic Activities**

**Papers**

**Presentations**

**Membership in Academic Society**

- The Japan Society of Plasma Science and Nuclear Fusion Research
- Japan Geoscience Union
- Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS)

**Awards**

- Review of Helicon High-Density Plasma:Production Mechanism and Plasma/ Wave Characteristics, Plasma and Fusion Research Vol. 13,1101014-1〜27(2018)

Educational

**Educational Activities**

Space Environmental Fluid Dynamics, Space Plasma Physics (regular lecture series + discussions)

Guest lectures at various foreign/domestic universities and academic institutes

Guest lectures at various foreign/domestic universities and academic institutes

Social

**Professional and Outreach Activities**

Science Council of Japan, Division of Earth and Planetary Science, STPP subcommittee, chair (2015-)

International research and education on space weather through ICSWSE (2012- )

International collaboration at the ISSI (International Space Science Institute), (2008-2010)

Public lectures on space environment, space exploration, and plasma propulsion systems(2007-)

Contribution of an article on the Mars Explorer Project to a local newspaper in Los Angeles (2000)

International collaboration at the ISSI (International Space Science Institute), (1998-1999).

International research and education on space weather through ICSWSE (2012- )

International collaboration at the ISSI (International Space Science Institute), (2008-2010)

Public lectures on space environment, space exploration, and plasma propulsion systems(2007-)

Contribution of an article on the Mars Explorer Project to a local newspaper in Los Angeles (2000)

International collaboration at the ISSI (International Space Science Institute), (1998-1999).

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