Dynamics of high‐energy electrons interacting with whistler mode chorus emissions in the magnetosphere
Dynamics of high‐energy electrons interacting with whistler mode chorus emissions in the magnetosphere
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DOI：
10.1029/2006ja011600
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发表时间：
2006-09
影响因子：
--
通讯作者：
Y. Omura;D. Summers
中科院分区：
文献类型：
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作者：
Y. Omura;D. Summers
[1] 对口哨模式合唱发射的仔细检查表明，合唱发射是一种相干单色波，通常具有快速上升的音调。发射频率随着波幅的增大而迅速增加。我们首先考虑口哨模式合唱发射的产生机制。频率变化的本质机制与赤道地区地磁场的不均匀性密切相关。只有当相干波远离赤道传播并与足够通量的逆流谐振电子相互作用时，才有可能出现升调发射。波相空间中共振俘获电子的耗尽导致电磁电子空穴的形成，从而产生横向共振电流，导致波生长和频率增加。上升音调的波增长可以拉长非线性捕获区，它作为有效的波列，引导一部分谐振电子向赤道移动。我们进行测试粒子模拟，求解相干哨声模式波的电磁场和假设的偶极地磁场作用下高能电子的相对论运动方程。我们发现一小部分弱相对论性电子被相干波捕获，并且被捕获的电子被具有上升音调的合唱波有效地加速。
[1] Close examination of whistler mode chorus emissions reveals that a chorus emission is a coherent monochromatic wave typically with a fast rising tone. The frequency of the emission increases rapidly along with growth of the wave amplitude. We first consider the generation mechanism of whistler mode chorus emissions. The essential mechanism of the frequency change is critically related to the inhomogeneity of the geomagnetic field in the equatorial region. The rising tone emission is only possible when the coherent wave propagates away from the equator interacting with a sufficient flux of counterstreaming resonant electrons. Depletion of the resonant trapped electrons from the wave phase space results in formation of an electromagnetic electron hole, which gives rise to a transverse resonant current causing both wave growth and frequency increase. The wave growth of a rising tone can elongate the nonlinear trapping zone, which works as an effective wave train that guides a fraction of the resonant electrons moving toward the equator. We perform test particle simulations where we solve the relativistic equations of motion for high-energy electrons under the action of the electromagnetic field of a coherent whistler mode wave and the assumed dipole geomagnetic field. We find that a fraction of weakly relativistic electrons are trapped by a coherent wave and that the trapped electrons are effectively accelerated by the chorus wave with a rising tone.