Chorus intensification in response to interplanetary shock
Chorus intensification in response to interplanetary shock
复制标题
DOI：
10.1029/2011ja016913
复制
发表时间：
2012
影响因子：
--
通讯作者：
H. Fu;J. Cao;F. Mozer;Haoyu Lu;B. Yang
中科院分区：
文献类型：
--
作者：
H. Fu;J. Cao;F. Mozer;Haoyu Lu;B. Yang
2009年9月3日，亚暴期间事件和大尺度相互作用的时间历史（THEMIS）卫星观测到，由于地球向阳面等离子体槽中的行星际激波，合唱显著增强。我们分析了波粒相互作用，并揭示了合唱团和高能电子之间的回旋共振可以引起合唱团的加强。当电子从共振点沿扩散曲线沿着向低密度区散射时，它们的一部分能量会损失，然后转移到放大合唱。在磁层压缩过程中，电子的温度各向异性增强。这使得电子扩散和合唱加强非常有效。冲击后的最大增长率比冲击前大50%左右。较低能量（15-25 keV）的电子有助于合唱团的增长，由于沿着扩散曲线的较大的密度梯度。< 10 keV的电子几乎是各向同性的，所以它们对合唱的放大贡献很小。我们调查的自由能的合唱加强，并发现它可以通过本地电子感应加速器加速和径向扩散过程中产生。局部电子感应加速器的加速是由冲击波引起的磁层压缩引起的。线性和非线性的增长率进行了比较。我们发现，线性扩散过程适用于目前的情况。
On 3 September 2009, the Time History of Events and Macroscale Interactions during Substorms (THEMIS) satellites observed a significant intensification of chorus in response to the interplanetary shock in the Earth's dayside plasma trough. We analyze the wave-particle interaction and reveal that the chorus intensification can be caused by the gyroresonance between the chorus and the energetic electrons. When the electrons are scattered from resonance points to low-density regions along the diffusion curves, a part of their energy can be lost and then transferred to amplify the chorus. During the compression of the magnetosphere, the temperature anisotropy of electrons is enhanced. This makes the electron diffusion and chorus intensification very effective. The maximum growth rate after the shock is about 50% greater than that before the shock. The lower-energy (15-25 keV) electrons contribute more to the growth of chorus due to the larger density gradient along the diffusion curve. The < 10 keV electrons are almost isotropic, so they contribute little to the amplification of chorus. We investigate the free energy for the chorus intensification and find that it can be generated through the local betatron acceleration and radial diffusion processes. The local betatron acceleration results from the shock-induced compression of the magnetosphere. The linear and nonlinear growth rates are also compared. We find that the linear diffusion process works well for the present case.