Trapping and acceleration of upflowing ionospheric electrons in the magnetosphere by electrostatic electron cyclotron harmonic waves
Trapping and acceleration of upflowing ionospheric electrons in the magnetosphere by electrostatic electron cyclotron harmonic waves
复制标题
DOI：
10.1002/2014gl062406
复制
发表时间：
2015-02
影响因子：
5.2
通讯作者：
R. Horne
中科院分区：
文献类型：
--
作者：
R. Horne
在地磁活动条件下，已经观察到能量高达100 eV的逆流场对准电子，它们构成了Birkland电流系统的一部分。如果第一个绝热不变量是守恒的，这些电子将到达共轭电离层而不会被困在磁层中。本文利用准线性扩散理论证明，静电电子回旋谐波（ECH）波可以通过多普勒频移回旋共振将这些低能电子沿俯角扩散并捕获在磁层中。我们发现能量扩散可以与俯仰角扩散相媲美，直到几个keV的能量。我们认为，ECH波在磁层中捕获电离层电子，并加速它们在能量高达几keV时产生蝴蝶俯仰角分布。我们认为，ECH波在磁层-电离层耦合中起作用，并有助于为辐射带提供源电子居数。
During geomagnetically active conditions upflowing field‐aligned electrons which form part of the Birkland current system have been observed at energies of up to 100 eV. If the first adiabatic invariant is conserved, these electrons would reach the conjugate ionosphere without trapping in the magnetosphere. Here we show, by using quasi‐linear diffusion theory, that electrostatic electron cyclotron harmonic (ECH) waves can diffuse these low‐energy electrons in pitch angle via Doppler‐shifted cyclotron resonance and trap them in the magnetosphere. We show that energy diffusion is comparable to pitch angle diffusion up to energies of a few keV. We suggest that ECH waves trap ionospheric electrons in the magnetosphere and accelerate them to produce butterfly pitch angle distributions at energies of up to a few keV. We suggest that ECH waves play a role in magnetosphere‐ionosphere coupling and help provide the source electron population for the radiation belts.