Full particle simulation of whistler-mode rising chorus emissions in the magnetosphere
Full particle simulation of whistler-mode rising chorus emissions in the magnetosphere
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DOI：
10.1029/2008ja013625
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发表时间：
2009-01-13
影响因子：
2.8
通讯作者：
Nagano, I.
中科院分区：
文献类型：
--
作者：
Hikishima, M.;Yagitani, S.;Nagano, I.
利用电磁全粒子模拟方法研究了磁层赤道区VLF哨声模式合唱辐射的产生机制。静态磁场的抛物线变化被假定为赤道附近偶极磁场的模型。我们有冷的热电子和相对低的各向异性热电子作为等离子体粒子。在初始阶段，非相干哨声波的振幅增长由线性增长率决定。当波的振幅达到一定水平时，它开始更快地增长，在磁赤道附近出现一系列由相干相位结构组成的上升音发射，并且它们的波包传播离开磁赤道。被激发的升调元素的频率扫描速率逐渐减小。我们发现这样一个非线性波增长产生的上升合唱类元素的一个明显的阈值。在模拟中发现的波的振幅和频率扫描率之间的关系，每个元素完全支持合唱发射的非线性波增长理论。
We perform an electromagnetic full particle simulation to study the generation mechanism of VLF whistler-mode chorus emissions in the equatorial region of the magnetosphere. Parabolic variation of the static magnetic field is assumed as a model for the dipole magnetic field in the vicinity of the equator. We have cold thermal electrons and relatively low anisotropic hot electrons as plasma particles. In the initial phase, the amplitude growth of the incoherent whistler-mode waves is determined by the linear growth rate. When the wave amplitude reaches a certain level, it begins to grow more rapidly with a series of rising tone emissions consisting of coherent phase structures in the vicinity of the magnetic equator, and their wave packets propagate away form the magnetic equator. The frequency sweep rates of the excited rising tone elements decrease gradually. We find a distinct threshold for such a nonlinear wave growth generating the rising chorus-like elements. The relation between the wave amplitude and the frequency sweep rate of each element found in the simulation fully supports the nonlinear wave growth theory of chorus emissions.