Study on three-dimensional magnetic reconnection based on formation-flying spacecraft observations of the magnetosphere

2018 Fiscal Year Annual Research Report

• Project/Area Number: 15K05306
• Research Institution: Japan Aerospace EXploration Agency
• Principal Investigator: 長谷川 洋 国立研究開発法人宇宙航空研究開発機構, 宇宙科学研究所, 助教 (50435799)
• Project Period (FY): 2015-04-01 – 2019-03-31
• Keywords: 磁気リコネクション / 衛星直接観測 / 磁気圏尾部 / 電子電磁流体力学

Outline of Annual Research Achievements

磁気リコネクションは太陽風プラズマの磁気圏侵入やオーロラ爆発の際のエネルギー解放に中心的な役割を果たしているが、地球周辺の宇宙空間では太陽風、バウショック下流の磁気圏シース、磁気圏界面、磁気圏尾部などで起きている。これらの領域で発生する磁気リコネクションは様々な境界条件を伴うため、複雑な条件下から単純な条件下まで、様々なタイプの磁気リコネクションを観測的に研究することができるという利点がある。NASAのMagnetospheric Multiscale（MMS）衛星は2017年7月11日に、最も単純な条件下、すなわち反平行磁場配位、かつ対称な電流層中で起きている磁気圏尾部の磁気リコネクションを観測することに成功した。本年度は、このMMS衛星が観測した磁気リコネクションの電子拡散領域と呼ばれる中心部の二次元構造を電子電磁流体の理論に基づいて再現し、単純な構造をしていると思われていた反平行・対称磁気リコネクション領域が、予想よりも複雑な構造をもつことを発見した。
具体的には、磁力線がつなぎ変わる場所であるXポイントと呼ばれる特異点と、電流層へと向かう電子の流れから電流層に沿った流れへと切り替わる「よどみ点」の場所が一致せず、よどみ点がリコネクションジェット方向にずれることを発見した。このような非対称構造が教科書的で単純なはずである反平行・対称磁気リコネクションの場合にも生じることは注目に値することである。また、Xポイントとよどみ点の場所がずれていたにもかかわらず、速い磁気リコネクションが実現していたことは驚きである。Xポイントとよどみ点のずれの原因はまだよく分かっていないが、Xポイントが背景プラズマに対して動いていたことと関係がある可能性があり、今後のさらなる研究が必要である。

Research Products

• [Int'l Joint Research] Dartmouth College/Southwest Research Institute/NASA Goddard Space Flight Center(米国)
  • Country Name: U.S.A.
  • Counterpart Institution: Dartmouth College/Southwest Research Institute/NASA Goddard Space Flight Center
  • # of Other Institutions: 7
• [Int'l Joint Research] Austrian Academy of Science(オーストリア)
  • Country Name: AUSTRIA
  • Counterpart Institution: Austrian Academy of Science
• [Int'l Joint Research] Uppsala University/Royal Institute of Technology(スウェーデン)
  • Country Name: SWEDEN
  • Counterpart Institution: Uppsala University/Royal Institute of Technology
• [Int'l Joint Research] University of Bergen(ノルウェー)
  • Country Name: NORWAY
  • Counterpart Institution: University of Bergen
• [Int'l Joint Research] Imperial College London/University College London(英国)
  • Country Name: UNITED KINGDOM
  • Counterpart Institution: Imperial College London/University College London
• [Int'l Joint Research]
  • # of Other Countries: 3
• [Journal Article] Reconstruction of the Electron Diffusion Region of Magnetotail Reconnection Seen by the MMS Spacecraft on 11 July 2017 (2019)
  • Author(s): Hasegawa H.、Denton R. E.、Nakamura R.、Genestreti K. J.、Nakamura T. K. M.、Hwang K.-J.、Phan T. D.、Torbert R. B.、Burch J. L.、Giles B. L.、Gershman D. J.、Russell C. T.、Strangeway R. J.、Lindqvist P.-A.、Khotyaintsev Y. V.、Ergun R. E.、Kitamura N.、Saito Y.
  • Journal Title: Journal of Geophysical Research: Space Physics Volume: 124 Pages: 122～138
  • DOI: https://doi.org/10.1029/2018JA026051
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Structure of the Current Sheet in the 11 July 2017 Electron Diffusion Region Event (2019)
  • Author(s): Nakamura Rumi、Genestreti Kevin J.、Nakamura Takuma、Baumjohann Wolfgang、Varsani Ali、Nagai Tsugunobu、Bessho Naoki、Burch James L.、Denton Richard E.、Eastwood Jonathan P.、Ergun Robert E.、Gershman Daniel J.、Giles Barbara L.、Hasegawa Hiroshi、et al.
  • Journal Title: Journal of Geophysical Research: Space Physics Volume: 124 Pages: 1173～1186
  • DOI: https://doi.org/10.1029/2018JA026028
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Crescent-shaped electron distributions at the non-reconnecting magnetopause: Magnetospheric Multiscale observations (2019)
  • Author(s): Tang B. -B.、Li W. Y.、Graham D. B.、Rager A. C.、Wang C.、Khotyaintsev Yu. V.、Lavraud B.、Hasegawa H.、Zhang Y. -C.、Dai L.、Giles B. L.、Dorelli J. C.、Russell C. T.、Lindqvist P. -A.、Ergun R. E.、Burch J. L.
  • Journal Title: Geophysical Research Letters Volume: 46 Pages: 3024～3032
  • DOI: https://doi.org/10.1029/2019GL082231
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Seasonal and Solar Wind Control of the Reconnection Line Location on the Earth's Dayside Magnetopause (2018)
  • Author(s): Hoshi Y.、Hasegawa H.、Kitamura N.、Saito Y.、Angelopoulos V.
  • Journal Title: Journal of Geophysical Research: Space Physics Volume: 123 Pages: 7498～7512
  • DOI: https://doi.org/10.1029/2018JA025305
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Measurement of the Magnetic Reconnection Rate in the Earth's Magnetotail (2018)
  • Author(s): Nakamura T. K. M.、Genestreti K. J.、Liu Y.‐H.、Nakamura R.、Teh W.‐L.、Hasegawa H.、Daughton W.、Hesse M.、Torbert R. B.、Burch J. L.、Giles B. L.
  • Journal Title: Journal of Geophysical Research: Space Physics Volume: 123 Pages: 9150～9168
  • DOI: https://doi.org/10.1029/2018JA025713
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Identifying 3-D Vortex Structures At/Around the Magnetopause Using a Tetrahedral Satellite Configuration (2018)
  • Author(s): Cai D.、Lembege B.、Hasegawa H.、Nishikawa K.-I.
  • Journal Title: Journal of Geophysical Research: Space Physics Volume: 123 Pages: 10,158～10,176
  • DOI: https://doi.org/10.1029/2018JA025547
  • Peer Reviewed / Int'l Joint Research
• [Presentation] Mass and energy transfer across the Earth’s magnetopause caused by the vortex-induced reconnection during northward IMF (2019)
  • Author(s): Nakamura, T. K. M., S. Eriksson, H. Hasegawa, K. Genestreti, R. Nakamura, W. Daughton, and W. Li
  • Organizer: MMS Community Science Workshop #4
  • Int'l Joint Research / Invited
• [Presentation] Test of polynomial reconstruction of the magnetic field (2019)
  • Author(s): Denton, R. E., R. B. Torbert, Y.-H. Liu, I. Dors, H. Hasegawa, B. U. O. Sonnerup, C. T. Russell, R. J. Strangeway, B. L. Giles, and J. L. Burch
  • Organizer: MMS Community Science Workshop #4
  • Int'l Joint Research
• [Presentation] Generation of turbulence in Kelvin-Helmholtz vortices at Earth’s magnetopause: MMS observations (2019)
  • Author(s): Hasegawa, H., T. K. M. Nakamura, D. J. Gershman, N. Kitamura, Y. Hoshi, Y. Saito, A. F.-Vinas, B. L. Giles, C. T. Russell, B. Lavraud, Y. V. Khotyaintsev, and R. E. Ergun
  • Organizer: ISEE symposium “Recent progress in heliospheric physics by direct measurements of unexplored space plasmas”
  • Int'l Joint Research
• [Presentation] Reconstruction of space plasma structures from in-situ measurements (2019)
  • Author(s): Hasegawa, H.
  • Organizer: Toyama International Symposium on “Physics at the Cosmic Frontier”
  • Int'l Joint Research / Invited
• [Presentation] On the generation of turbulence observed in the flank of Earth's magnetosphere (2018)
  • Author(s): H. Hasegawa, T. K. M. Nakamura, D. J. Gershman, N. Kitamura, Y. Hoshi, Y. Saito, A. F.-Vinas, B. L. Giles, C. T. Russell, B. Lavraud, Y. V. Khotyaintsev, and R. E. Ergun
  • Organizer: JpGU 2018 Meeting
  • Int'l Joint Research
• [Presentation] Mass and energy transfer across the Earth's magnetopause caused by vortex-induced reconnection (2018)
  • Author(s): Nakamura, T. K. M., H. Hasegawa, S. Eriksson, W. Daughton, W. Y. Li, S. Zenitani, K. Genestreti, and R. Nakamura
  • Organizer: COSPAR 2018 42nd Assembly
  • Int'l Joint Research / Invited
• [Presentation] Reconstruction of the magnetotail reconnection region seen by MMS on 11 July 2017 (2018)
  • Author(s): Hasegawa, H., R. E. Denton, R. Nakamura, K. J. Genestreti, T. K. M. Nakamura, T. D. Phan, R. B. Torbert, J. L. Burch, B. L. Giles, D. J. Gershman, C. T. Russell, R. J. Strangeway, P.-A. Lindqvist, Y. V. Khotyaintsev, R. E. Ergun, N. Kitamura, and Y. Saito
  • Organizer: MMS Science Community Workshop #3
  • Int'l Joint Research
• [Presentation] Determining the velocity of a magnetic structure, with application to the 11 July 2017 magnetotail reconnection event (2018)
  • Author(s): R. E. Denton, R. Manuzzo, K. J. Genestreti, B. U. O. Sonnerup, G. Belmont, L. Rezeau, H. Hasegawa, C. T. Russell, R. J. Strangeway, R. B. Torbert, and J. L. Burch
  • Organizer: MMS Science Community Workshop #3
  • Int'l Joint Research
• [Presentation] Reconstruction of the electron diffusion region of magnetotail reconnection seen by the MMS spacecraft on 11 July 2017 (2018)
  • Author(s): Hasegawa, H., R. E. Denton, R. Nakamura, K. J. Genestreti, T. K. M. Nakamura, K.-J. Hwang, T. D. Phan, R. B. Torbert, J. L. Burch, B. L. Giles, D. J. Gershmain, C. T. Russell, R. J. Strangeway, P.-A. Lindqvist, Y. V. Khotyaintsev, R. E. Ergun, N. Kitamura, and Y. Saito
  • Organizer: Magnetic Reconnection in Space, Solar, Astrophysical, and Laboratory Plasmas (MR2018)
  • Int'l Joint Research / Invited
• [Presentation] The structure and geometry of magnetic reconnection regions (2018)
  • Author(s): Genestreti, K. J., J. L. Burch, R. B. Torbert, R. Nakamura, T. K. M. Nakamura, A. Varsani, C. Mouikis, M. R. Argall, S. A. Fuselier, P. A. Cassak, R. E. Ergun, H. Hasegawa, J. M. Webster, S. Wang, T.-D. Phan, M. Hesse, C. Norgren, P. Tenfjord, J. Eastwood, J. Stawarz, and S. Toledo-Redondo
  • Organizer: Magnetic Reconnection in Space, Solar, Astrophysical, and Laboratory Plasmas (MR2018)
  • Int'l Joint Research / Invited
• [Presentation] MMS衛星がみた地球磁気圏尾部リコネクション領域の構造 (2018)
  • Author(s): 長谷川 洋
  • Organizer: 宇治リコネクションワークショップ2018