FAST observations in the downward auroral current region: Energetic upgoing electron beams, parallel potential drops, and ion heating
FAST observations in the downward auroral current region: Energetic upgoing electron beams, parallel potential drops, and ion heating
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DOI：
10.1029/98gl00851
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发表时间：
1998-06
影响因子：
5.2
通讯作者：
C. Carlson;J. Mcfadden;R. Ergun;M. Temerin;W. Peria;F. Mozer;D. Klumpar;E. Shelley;W.K. (Bill) Peterson;E. Moebius;R. Elphic;R. Strangeway;C. Cattell;R. Pfaff
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文献类型：
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作者：
C. Carlson;J. Mcfadden;R. Ergun;M. Temerin;W. Peria;F. Mozer;D. Klumpar;E. Shelley;W.K. (Bill) Peterson;E. Moebius;R. Elphic;R. Strangeway;C. Cattell;R. Pfaff
FAST卫星对等离子体粒子和电场的观测发现，有证据表明，准静态平行电场加速了强烈的上行电子束。束流特性包括能量谱宽，峰值能量在100 eV到5 keV之间，垂直温度小于1 eV，束流密度大于109/cm2·s。与束流相关的发散静电冲击具有与束流能量相匹配的积分势。这些束流位于向下的伯克兰流区域，当它们存在时，它们就构成了总场向电流。极光区最高能量的离子二次曲线被发现与这些光束重合，这与“囚禁”二次曲线的模型一致。电子束和相关离子二次曲线的测量粒子密度大致相等，通常范围从1到10厘米−3，没有证据表明存在额外的冷密度。这些光束经常出现在冬季极光区海拔2000至4000公里的地方。它们的出现概率与季节和海拔高度有很强的相关性，与邻近上升流区的上行离子束的出现概率相似。这种相似性表明，电离层离子的密度和尺度高度在这两种束流的形成中起着重要作用。
Observations of plasma particles and fields by the FAST satellite find evidence of acceleration of intense upgoing electron beams by quasi‐static parallel electric fields. The beam characteristics include a broad energy spectrum with peak energies between 100 eV and 5 keV, perpendicular temperatures less than 1 eV, and fluxes greater than 109/cm²sec. Diverging electrostatic shocks associated with the beams have integrated potentials that match the beam energy. These beams are found in regions of downward Birkeland current and account for the total field‐aligned current when they are present. The most energetic ion conics in the auroral zone are found coincident with these beams, in agreement with the model for “trapped” conics. The measured particle densities of the electron beams and associated ion conics are approximately equal and typically range from 1 to 10 cm−3, with no evidence for additional cold density. The beams are seen frequently at altitudes between 2000 and 4000 km in the winter auroral zone. Their probability of occurrence has a strong dependence on season and altitude and is similar to that for upgoing ion beams in the adjacent upward current regions. This similarity suggests that the density and scale height of ionospheric ions play an important role in the formation of both types of beams.