相対論的プラズマ不安定性
キーワード：相対論的プラズマ、シンクロトロン放射、メーザー不安定性、パラメトリック不安定性、粒子加速
2020.04.

太陽圏外縁構造の解明と宇宙線の侵入・輸送過程
キーワード：太陽圏、宇宙線、終端衝撃波、太陽圏界面
2017.04.

地球磁気圏衝撃波のフォアショック構造と粒子加速
キーワード：磁気圏衝撃波、フォアショック、粒子加速
2015.09.

無衝突衝撃波の実験的研究
キーワード：レーザー実験、無衝突衝撃波
2013.04.

太陽圏終端衝撃波の構造と粒子加速
キーワード：終端衝撃波、粒子加速、ピックアップイオン
2007.05.

星表面近傍における多イオン種プラズマ中の非線形波動励起と粒子加速過程
キーワード：粒子加速、多イオン種プラズマ
2010.04～2012.03.

無衝突衝撃波の基礎物理
キーワード：非定常衝撃波、異常散逸、微視的不安定性、スケール間結合
2002.05.

宇宙プラズマにおける相対論的粒子加速
キーワード：相対論的プラズマ、高エネルギー粒子加速、宇宙線
2005.01.

宇宙プラズマにおける大振幅波動-波動および波動-粒子相互作用
キーワード：大振幅波動、波動-波動相互作用、波動-粒子相互作用
1999.01.

パワーレーザーを用いた無衝突衝撃波生成と粒子加速
2022.04～2026.03, 代表者：坂和洋一, 大阪大学.

高速磁気リコネクションとそのエネルギー変換過程の解明を目指すレーザープラズマ 実験
2024.04～2026.03, 代表者：森田太智, 九州大学, 九州大学.

「富岳」成果創出加速プログラム「シミュレーションとAIの融合で解明する宇宙の構造と進化」
2023.04～2026.03.

グローバル太陽圏における宇宙線加速・輸送の粒子シミュレーション
2022.04～2025.03, 代表者：松清修一, 九州大学, 九州大学
広大な太陽圏境界のどこで宇宙線異常成分が加速されるのか、また圏外からの銀河宇宙線の侵入過程に太陽圏構造がどのように寄与するのか、という２つの本質的な問題の解明に挑む。太陽圏のグローバル3次元構造を高精度磁気流体計算で再現し、これと有機的に結合した2種類の大型粒子計算を展開する。フル粒子計算では終端衝撃波における宇宙線異常成分の加速機構・効率を明らかにする。テスト粒子計算では圏外からの銀河宇宙線の侵入～地球への輸送過程を粒子軌道レベルで解き明かす。以上により、宇宙線加速の標準モデルとされる衝撃波粒子加速モデルの改良と、地球で観測される宇宙線の太陽モジュレーション効果の高精度モデルの構築を目指す。.

「富岳」成果創出加速プログラム「宇宙の構造形成と進化から惑星表層環境変動までの統一的描像の構築」
2020.04～2023.03.

Intrinsic dynamics of collisionless shocks and nonthermal particle acceleration
2020.11, 代表者：蔵満康浩, 大阪大学.

高出力レーザー生成プラズマを用いる磁気リコネクションの実験研究
2020.04～2024.03, 代表者：森田太智, 九州大学, 九州大学.

宇宙線の加速・輸送における太陽圏境界の役割の解明
2019.04～2022.03, 代表者：松清修一, 九州大学, 九州大学.

直接観測に基づく衝撃波電子加速の実証的理論モデルの確立
2017.04～2021.03, 代表者：天野孝信, 東京大学
人工衛星の高解像度データと数値シミュレーションを用いて、無衝突衝撃波での電子加速機構を解明する.

大型高強度レーザーを用いた宇宙物理学実験
2015.04～2019.03, 代表者：坂和洋一, 大阪大学
高強度レーザーを用いた実験室宇宙物理の確立を目指した実験的研究.

衝撃波フェルミ加速過程における沿磁力線ビームの役割
2015.09～2017.08, 代表者：松清修一, 九州大学, 九州大学
地球磁気圏衝撃波上流（＝フォアショック）における同時多点衛星観測で、従来考えられているよりも高効率の粒子加速が起こっていることが示唆された。地球磁気圏のフォアショックではしばしば衝撃波で反射されて上流に向けて背走する沿磁力線ビームが観測されており、ここでは、これが励起する波動が高エネルギー粒子を効率的に散乱して加速効率を上げる、というモデルを提案し、数値実験と衛星データ解析によってその検証を目指す。 .

名古屋大学HPC計算科学連携研究プロジェクト
2014.04～2015.03, 代表者：松清修一, 九州大学, 名古屋大学（日本）
名古屋大学情報基盤センター、地球水循環研究センター、太陽地球環境研究所の３部局が連携して名大情報基盤センターのスーパーコンピュータを利用するHPC 計算科学共同研究プロジェクト。研究代表者として「無衝突衝撃波遷移層における微視的不安定性の多次元実パラメータ計算」と題した大型フル粒子シミュレーションを遂行する（2013年度から継続）。.

名古屋大学HPC計算科学連携研究プロジェクト
2013.04～2014.03, 代表者：松清修一, 九州大学, 名古屋大学（日本）
名古屋大学情報基盤センター、地球水循環研究センター、太陽地球環境研究所の３部局が連携して名大情報基盤センターのスーパーコンピュータを利用するHPC 計算科学共同研究プロジェクト。研究代表者として「無衝突衝撃波遷移層における微視的不安定性の多次元実パラメータ計算」と題した大型フル粒子シミュレーションを遂行する。.

Physics of the Injection of Particle Acceleration at Astrophysical, Heliospheric, and Laboratory Collisionless Shocks
2013.07～2015.07, 代表者：Shuichi Matsukiyo and Ryo Yamazaki, Kyushu Univ. and Aoyama Gakuin Univ., International Space Science Institute (ISSI) (Switzerland)
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.
.

太陽圏終端衝撃波のミクロ～メゾスケール構造と粒子加速
2013.04～2016.03, 代表者：松清修一, 九州大学, 九州大学
　地球で観測される宇宙線のエネルギースペクトルは、数十メガeV付近にピークを持つ。これは宇宙線異常成分と呼ばれ、太陽圏の外縁部に形成される太陽圏終端衝撃波で加速されたものであると長年考えられてきた。宇宙線異常成分の存在は、衝撃波による宇宙線加速モデルが現在広く受け入れられている根拠の一つとされている。ところが、2機のボイジャー探査機が終端衝撃波を通過した際、期待したような粒子加速の徴候は見られず、その原因は大きな謎となっている。本研究の目的は、終端衝撃波の基本構造とその粒子加速器としての能力を解明することにある。この際、太陽圏外縁のプラズマに多く含まれるピックアップイオンがこれに与える影響を陽に考慮するとともに、これまであまり注目されることのなかった電子加速についても議論する。
.

高マッハ数非定常衝撃波の観測的実証研究に向けた数値実験
2010.04～2013.03, 代表者：松清修一, 九州大学
　高マッハ数無衝突衝撃波の非定常的振る舞いのうち、リフォーメーションと呼ばれる衝撃波面の周期的な形成・崩壊過程に注目した。リフォーメーションは、数値実験によって予言された高マッハ数衝撃波の自発的な振る舞いであり、その観測的実証は未だなされていない。ここでは、リフォーメーションの基本特性を数値実験により明らかにし、特にこれに付随して起こる反射電子バーストに着目して、衛星観測の際にこれをリフォーメーションのメジャーとして用いるための知見を得た。
.

平成22年度計算機利用共同研究
2010.04～2011.03, 代表者：松清修一, 九州大学大学院総合理工学研究院, 宇宙航空研究開発機構（日本）
プラズマ粒子シミュレーションによる非定常衝撃波に関する研究.

次世代第一原理粒子シミュレーションによる無衝突衝撃波の粒子加速機構の解明
2009.04～2012.03, 代表者：梅田隆行, 名古屋大学
次世代第一原理プラズマ粒子シミュレーションを用いて、マルチスケール・マルチ物理過程が本質的な無衝突衝撃波における粒子加速機構の解明を目指す。.

高マッハ数無衝突衝撃波における散逸機構としての微視的不安定性
2007.04～2010.03, 代表者：松清修一, 九州大学
　宇宙・天体プラズマにおいてしばしば観測される無衝突衝撃波では、上流の流れのエネルギーは電磁場を介した波動ー粒子相互作用によって散逸される。散逸過程の詳細は、比較的低マッハ数の衝撃波に対してはよく理解されているが、高マッハ数の場合はいくつかの重要な未解決問題を残している。現在進行中の水星探査計画（BepiColombo計画）では、水星軌道近傍を通過する幅広いマッハ数の惑星間空間衝撃波が観測されることが期待されているが、これに先駆けて高マッハ数衝撃波に関する以下の２つの未解決問題を議論し、それぞれに対する理論的枠組みを構築する。
１．遷移層における微視的不安定性による電子加熱効率の定量的評価、および効率的な加熱が起こる上流パラメータの見積もり
２．マッハ数上昇に伴う主要散逸機構の変遷の可能性の検討
.

主要著書

主要原著論文

1.	Matsukiyo, S.; Yamazaki, R.; Morita, T.; Tomita, K. ; Kuramitsu, Y. ; Sano, T. ; Tanaka, S. J. ; Takezaki, T.; Isayama, S.; Higuchi, T.; Murakami, H.; Horie, Y.; Katsuki, N.; Hatsuyama, R.; Edamoto, M.; Nishioka, H.; Takagi, M.; Kojima, T.; Tomita, S.; Ishizaka, N.; Kakuchi, S.; Sei, S.; Sugiyama, K.; Aihara, K.; Kambayashi, S.; Ota, M.; Egashira, S.; Izumi, T.; Minami, T.; Nakagawa, Y.; Sakai, K.; Iwamoto, M.; Ozaki, N.; Sakawa, Y., High-power laser experiment on developing supercritical shock propagating in homogeneously magnetized plasma of ambient gas origin, Physical Review E, 10.1103/PhysRevE.106.025205, 106, 025205, 2022.08, [URL].
2.	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].
3.	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..
4.	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..
5.	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].
6.	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].
7.	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.
8.	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].
9.	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].
10.	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].
11.	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].
12.	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].
13.	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].
14.	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].
15.	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].
16.	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].
17.	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].
18.	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].
19.	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].
20.	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].

主要総説, 論評, 解説, 書評, 報告書等

1.	Shuichi Matsukiyo, 無衝突衝撃波とプラズマの局所相互作用：波動、多スケール物理、粒子加速・加熱, プラズマ核融合学会誌, 2016.02, [URL].
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.	Shuichi Matsukiyo, 無衝突衝撃波におけるピックアップイオンの役割：パラメータ調査, 2013.09.
6.	Shuichi Matsukiyo, 無衝突衝撃波におけるピックアップイオンの役割, 2012.09.
7.	Shuichi Matsukiyo, プラズマ粒子シミュレーションによる非定常衝撃波に関する研究, 2011.09.
8.	松清 修一, プラズマ粒子シミュレーションによる非定常衝撃波に関する研究, 2010.09.
9.	松清 修一, 種々の不安定性に伴う高マッハ数衝撃波における電子加熱, 2009.09.
10.	松清 修一, 高マッハ数撃波近傍における荷電粒子の加速・加熱に関する数値実験, 2008.09, [URL].
11.	松清 修一, 無衝突衝撃波近傍における荷電粒子の加速・加熱に関する数値実験, 2007.09, [URL].
12.	松清 修一, 長谷川 毅, 宇宙プラズマ中の無衝突衝撃波近傍における波動－粒子相互作用, 2006.09, [URL].
13.	松清修一, 宇宙プラズマ衝撃波近傍における微視的不安定性と高エネルギー粒子生成過程の数値実験, 2006.07.
14.	松清 修一, 宇宙プラズマ中の無衝突衝撃波遷移領域における波動－粒子相互作用, 2005.09, [URL].

主要学会発表等

1.	S. Matsukiyo, Generation of nonthermal pickup ions in an oblique heliospheric termination shock, 21st Annual International Astrophysics Conference, 2024.03, [URL].
2.	松清修一、松本洋介, 太陽圏終端衝撃波における宇宙線異常成分の初期加速, 日本物理学会2024年春季大会, 2024.03, [URL].
3.	S. Matsukiyo, 太陽圏構造と宇宙線の加速・輸送, ISEE研究集会：太陽圏の次世代研究検討会「太陽圏プラズマ物理におけるマルチメッセンジャー研究の進展」, 2024.03.
4.	S. Matsukiyo, Nonstationarity of a Collisionless Shock, International Workshop on New Developments in Laboratory Astrophysics, 2024.01.
5.	S. Matsukiyo, Effects of heliospheric boundary in the behaviors of galactic and anomalous cosmic rays, 7th Asia-Pacific Conference on Plasma Physics, 2023.11, [URL].
6.	S. Matsukiyo, K. Yoshida, H. Washimi, T. Hada, Properties of cosmic ray test particles in global MHD simulation of the heliosphere, EGU General Assembly 2022, 2022.05, [URL].
7.	S. Matsukiyo, K. Yoshida, H. Washimi, T. Hada, Properties of cosmic ray test particles invading the virtual heliosphere in global MHD simulation, 20th Annual International Astrophysics Conference, 2022.10, [URL].
8.	S. Matsukiyo, R. Yamazaki, T. Morita, T. Takezaki, Y. Kuramitsu, T. Sano, K. Tomita, S-J. Tanaka, S. Isayama, M. Iwamoto, M. Ota, S. Egashira, K. Sakai, T. Minami, M. Edamoto, S. Tomita, N. Ozaki, Y. Sakawa, Gekko XII High Power Laser Experiment and Numerical Simulation on Developing Supercritical Magnetized Shock, 20th International Congress on Plasma Physics, 2022.11, [URL].
9.	松清 修一, 松田 昇也, 地球電磁気・地球惑星圏学会 波動分科会, 宇宙プラズマ波動研究の将来構想, 第150回 地球電磁気･地球惑星圏学会講演会, 2021.11, [URL].
10.	S. Matsukiyo, S. Isayama, T. Morita, T. Takezaki, K. Tomita, R. Yamazaki, Y. Kuramitsu, S.-J. Tanaka, T. Sano, M. Iwamoto, H. Luo, K. Takahashi, R. Higashi, S. Egashira, M. Ohta, H. Ishihara, Y. Nakagawa, O. Kuramoto, Y. Matsumoto, T. Minami, K. Sakai, T. Nishimoto, K. Iwasaki, K. Himeno, T. Taguchi, M. Edamoto, T. Kojima, S. Matsuo, E. Kuramoto, Y. Sato, K. Obayashi, K. Aihara, Y. Sato, S. Ide, T. Oguchi, Y. Sakawa, High power laser experiment on collisionless shocks and the associated PIC simulation, 5th Asia-Pacific Conference on Plasma Physics, 2021.09, [URL].
11.	松清修一, 大塚史子, Arpad Kis, 地球フォアショックULF 波動による高エネルギーイオンの拡散過程, 2020年度ISEE研究集会「太陽地球環境と宇宙線モジュレーション」、 「惑星間空間プラズマにおける波動現象」, 2021.02.
12.	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..
13.	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..
14.	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..
15.	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..
16.	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..
17.	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..
18.	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..
19.	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..
20.	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
21.	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].
22.	Shuichi Matsukiyo, Electron acceleration at a high beta shock, 14th Annual International Astrophysics Conference, 2015.04, [URL].
23.	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.
24.	松清 修一, 高マッハ数無衝突衝撃波生成の理論, 日本物理学会2013年秋季大会, 2013.09, [URL].
25.	松清 修一, PIC simulations of the termination shock, 8th European Workshop on Collisionless shocks, 2013.06, [URL].
26.	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..
27.	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..
28.	Shuichi Matsukiyo, Manfred Scholer, Full Particle Simulation on Microstructure of Heliospheric Termination Shock, 2011 International Space Plasma Symposium (ISPS2011), 2011.08, [URL].
29.	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].
30.	Shuichi Matsukiyo, Manfred Scholer, Nonthermal electrons produced by supercritical quasi-perpendicular shocks, 2010 International Space Plasma Symposium, 2010.06, [URL].
31.	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].
32.	Shuichi Matsukiyo, Manfred Scholer, Electron heating through microinstabilities in high Mach number quasi-perpendicular shocks, 8TH Annual International Astrophysics Conference, 2009.05, [URL].
33.	Shuichi Matsukiyo, Relativistic particle acceleration in developing Alfven turbulence, KINETIC MODELING OF ASTROPHYSICAL PLASMAS, 2008.10, [URL].
34.	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.
35.	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.
36.	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].
37.	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].
38.	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.
39.	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].
40.	Shuichi Matsukiyo, Manfred Scholer, Microinstabilities in collisionless shocks: recent simulation results, URSI (XXVIIIth General Assembly of International Union of Radio Science), 2005.10.
41.	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.

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