Entropy mapping of the outer electron radiation belt between the magnetotail and geosynchronous orbit
Entropy mapping of the outer electron radiation belt between the magnetotail and geosynchronous orbit
复制标题
磁尾与地球同步轨道之间外电子辐射带的熵图
DOI：
10.1029/2011ja016470
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发表时间：
2011
影响因子：
--
通讯作者：
T. Cayton
中科院分区：
文献类型：
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作者：
J. Borovsky;T. Cayton
[1]研究了地球同步轨道外电子辐射带和地球磁尾高能电子布居的比熵（熵密度）S。外电子辐射带是用六颗地球同步卫星上的SOPA探测器测量的，磁尾的高能电子是用12颗全球定位卫星上的仪器测量的，该卫星带有一个磁场模型，用于将全球定位卫星轨道映射到磁尾。密度n和温度T值由相对论麦克斯韦拟合电子测量值确定，从而能够计算出比熵S。对于低温，非相对论性比熵为S = T/n ~ 2/3;对于相对论性麦克斯韦分布，导出并使用了S = S（T，n）的相对论性正确表达式。在地球同步轨道午夜的外层电子辐射带（n = 3 × 10−4 cm−3，T = 140 keV）和磁尾的高能电子布居（n = 1 × 10−4 cm−3，T = 50 keV）在统计上具有相同的比熵。因此，这两个种群可能是相同的。这意味着绝热传输（1）从磁尾到偶极子（其中磁尾电子是外部电子辐射带的源）或（2）从偶极子到磁尾（其中磁尾电子是辐射带的泄漏）。
[1] The specific entropy (entropy density) S is examined for the outer electron radiation belt at geosynchronous orbit and for the energetic electron population in the Earth's magnetotail. The outer electron radiation belt is measured with the SOPA detectors on board six geosynchronous satellites and the energetic electrons of the magnetotail are measured with instrumentation on board 12 Global Positioning Satellites (GPS) with a magnetic field model used to map the GPS orbit to the magnetotail. Density n and temperature T values are determined from relativistic Maxwellian fits to the electron measurements, enabling the specific entropy S to be calculated. For low temperatures the nonrelativstic specific entropy is S = T/n2/3; for a relativistic Maxwellian distribution a relativistically correct expression for S = S(T,n) is derived and used. The outer electron radiation belt at geosynchronous orbit local midnight (n ∼ 3 × 10−4 cm−3 and T ∼ 140 keV) and the energetic-electron population in the magnetotail (n ∼ 1 × 10−4 cm−3 and T ∼ 50 keV) statistically have the same specific entropy. Hence the two populations are probably the same. This implies adiabatic transport (1) from the magnetotail to the dipole (where the magnetotail electrons are the source of the outer electron radiation belt) or (2) from the dipole to the magnetotail (where the magnetotail electrons are leakage from the radiation belt).