Coupling of electrons and inertial Alfven waves in the topside ionosphere
Coupling of electrons and inertial Alfven waves in the topside ionosphere
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DOI：
10.1002/jgra.50355
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发表时间：
2013-06
期刊：
影响因子：
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通讯作者：
R. Shi;Huixin Liu;A. Yoshikawa;Beichen Zhang;B. Ni
中科院分区：
文献类型：
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作者：
R. Shi;Huixin Liu;A. Yoshikawa;Beichen Zhang;B. Ni
建立了一个一维动力学模型来模拟惯性阿尔芬波对电子的加速。电子分为冷电子和热电子，并分别处理。冷分量由流体方程描述，热分量由弗拉索夫方程描述，两者都携带场向电流。阿尔芬速度的剧烈变化已被引入冷电子。模型结果表明，等离子体密度的指数下降是导致Alfven速度和电子惯性长度均出现急剧梯度的关键因素。当阿尔芬波在较低的高度遇到这种急剧的梯度时，被波加速的电子变得超阿尔芬，爆发结构的宽度变得比电子惯性长度宽得多。因此，由于等离子体振荡，背景电子携带相反的场对准电流。结果表明，超过波前的电子所携带的电流被背景电子所携带的反向电流所平衡。这种机制可以用来合理地解释伴随着小净场向电流的电子爆发的观察。此外，我们的模拟表明另一种类型的阿尔芬波反射由于镜力和波粒相互作用。
A one‐dimensional kinetic model is constructed to simulate the electron acceleration by inertial Alfven waves. The electrons are divided into cold and hot electrons and treated separately. Cold components are described by the fluid equation and hot ones by the Vlasov equation, both carrying field‐aligned currents. Intense variation of Alfven speed has been introduced by inclusion of cold electrons. The model results show that the exponential decrease of the plasma density plays a key role, which leads to the sharp gradient of both Alfven velocity and electron inertial length. When Alfven waves encounter this sharp gradient at lower altitudes, the electrons accelerated by the waves become super‐Alfvenic, and the width of burst structures becomes much wider than the electron inertial length. Consequently, the background electrons carry the oppositely field‐aligned current due to plasma oscillation. It is demonstrated that the current carried by the electrons exceeding the wavefront is balanced by the reverse current carried by background electrons. This mechanism can be used to reasonably explain observations of the electron bursts accompanied by little net field‐aligned current. Furthermore, our simulation indicates another type of Alfven wave reflection due to mirror force and wave‐particle interaction.