Generation of anisotropic electron distributions in the Earth's magnetosphere
學年 104
學期 2
發表日期 2016-06-27
作品名稱 Generation of anisotropic electron distributions in the Earth's magnetosphere
作品名稱（其他語言）
著者 Tohru Hada; Wang, Kaiti
作品所屬單位
出版者
會議名稱 18th International Congress on Plasma Physics
會議地點 Kaohsiung, Taiwan
摘要 Anisotropic electron distributions are often found in the earth’s magnetotail, in the energy range from about 10eV to 10keV [1-3]. Theoretical models are proposed to account for these distributions, based on parallel (Fermi) and perpendicular (betatron) electron heating due to deformation of the magnetic field lines [1]. Recently, Wang et al. (2014) made a statistical analysis of the variation of the electron pitch-angle anisotropies during geomagnetic dipolarization events using THEMIS data [3]. They found that, after the dipolarization, pancake type (perp temperature > parallel) anisotropy increases when the electron energy E < ~1keV, while cigar type (perp < parallel) anisotropy dominates for E>~1keV. When typical parameters are used for the magnetic field and the electron energy, the first adiabatic invariant is always conserved while the second invariant (action associated with the mirroring motion) can be violated depending on the electron energy. When both the first and the second invariants are conserved, types of anisotropy produced by compression of the field depend only on the shape of the magnetic field configuration. If the field remains dipolar, pancake type will be produced. If the magnetic field lines are stretched like those in the magnetotail, cigar-type anisotropy will be produced, since compression (earthward motion) of the field reduces the field line length without much changing the field strength. In this presentation we show our results of test particle simulations to discuss what types of pitch-angle anisotropies would emerge for various field line configurations. In particular, we show that the observed dependence of the types of anisotropies on the electron energy can roughly be explained in the present model.
關鍵字
語言 en
收錄於
會議性質 國際
校內研討會地點 無
研討會時間 20160627~20160701
通訊作者 Tohru Hada
國別 TWN
公開徵稿
出版型式
出處 Book of Abstracts, ICPP 2016, pp.C1P1-5
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機構典藏連結 ( http://tkuir.lib.tku.edu.tw:8080/dspace/handle/987654321/107556 )

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