Magnetic Field Annihilation in a Magnetotail Electron Diffusion Region With Electron-Scale Magnetic Island.

Autor: Hasegawa H; Institute of Space and Astronautical Science Japan Aerospace Exploration Agency Sagamihara Japan., Denton RE; Department of Physics and Astronomy Dartmouth College Hanover NH USA., Nakamura TKM; Space Research Institute Austrian Academy of Sciences Graz Austria.; Institute of Physics University of Graz Graz Austria., Genestreti KJ; Southwest Research Institute Durham NH USA., Phan TD; Space Sciences Laboratory University of California Berkeley CA USA., Nakamura R; Space Research Institute Austrian Academy of Sciences Graz Austria., Hwang KJ; Southwest Research Institute San Antonio TX USA., Ahmadi N; Laboratory for Atmospheric and Space Physics University of Colorado Boulder CO USA., Shi QQ; Shandong Provincial Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment Institute of Space Sciences Shandong University Weihai China., Hesse M; NASA Ames Research Center Moffett Field CA USA., Burch JL; Southwest Research Institute San Antonio TX USA., Webster JM; Southwest Research Institute San Antonio TX USA., Torbert RB; Institute of Physics University of Graz Graz Austria.; Physics Department University of New Hampshire Durham NH USA., Giles BL; NASA Goddard Space Flight Center Greenbelt MD USA., Gershman DJ; NASA Goddard Space Flight Center Greenbelt MD USA., Russell CT; Department of Earth, Planetary, and Space Sciences University of California Los Angeles CA USA., Strangeway RJ; Department of Earth, Planetary, and Space Sciences University of California Los Angeles CA USA., Wei HY; Department of Earth, Planetary, and Space Sciences University of California Los Angeles CA USA., Lindqvist PA; Royal Institute of Technology Stockholm Sweden., Khotyaintsev YV; Swedish Institute of Space Physics Uppsala Sweden., Ergun RE; Department of Astrophysical and Planetary Sciences University of Colorado Boulder CO USA., Saito Y; Institute of Space and Astronautical Science Japan Aerospace Exploration Agency Sagamihara Japan.
Jazyk: angličtina
Zdroj: Journal of geophysical research. Space physics [J Geophys Res Space Phys] 2022 Jul; Vol. 127 (7), pp. e2022JA030408. Date of Electronic Publication: 2022 Jul 07.
DOI: 10.1029/2022JA030408
Abstrakt: We present observations in Earth's magnetotail by the Magnetospheric Multiscale spacecraft that are consistent with magnetic field annihilation, rather than magnetic topology change, causing fast magnetic-to-electron energy conversion in an electron-scale current sheet. Multi-spacecraft analysis for the magnetic field reconstruction shows that an electron-scale magnetic island was embedded in the observed electron diffusion region (EDR), suggesting an elongated shape of the EDR. Evidence for the annihilation was revealed in the form of the island growing at a rate much lower than expected for the standard X-type geometry of the EDR, which indicates that magnetic flux injected into the EDR was not ejected from the X-point or accumulated in the island, but was dissipated in the EDR. This energy conversion process is in contrast to that in the standard EDR of a reconnecting current sheet where the energy of antiparallel magnetic fields is mostly converted to electron bulk-flow energy. Fully kinetic simulation also demonstrates that an elongated EDR is subject to the formation of electron-scale magnetic islands in which fast but transient annihilation can occur. Consistent with the observations and simulation, theoretical analysis shows that fast magnetic diffusion can occur in an elongated EDR in the presence of nongyrotropic electron effects. We suggest that the annihilation in elongated EDRs may contribute to the dissipation of magnetic energy in a turbulent collisionless plasma.
(© 2022. The Authors.)
Databáze: MEDLINE
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