Passing the Alfven Layer by Means of Chorus Acceleration
Passing the Alfven Layer by Means of Chorus Acceleration
复制标题
通过合唱加速通过阿尔芬层
DOI：
10.1002/essoar.10510991.1
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发表时间：
2022
期刊：
影响因子：
--
通讯作者：
Allison H
中科院分区：
文献类型：
--
作者：
Allison H
持续向南的行星际磁场会导致强烈的磁层对流，在此期间，分离向太阳对流和封闭漂移路径区域的阿尔文层向地球迁移。等离子体层电子可以直接进入内磁层，在穿过磁层顶之前穿过黎明区，并为辐射带提供潜在的种子种群。在这里，我们首次研究了高能电子在漂移过程中是否可以通过与哨子模式合唱波的共振相互作用获得足够的能量，从而在离开系统之前通过阿尔芬层。我们利用磁层对流的自然坐标系，（U，B，K）空间，在其中我们计算了漂移轨迹，开放漂移路径上的电子能量和漂移时间。首先采用通用电子辐射带模型（VERB）作为二维扩散方程，然后采用四维对流扩散模式计算共振共振-波粒子相互作用的加速时间。将漂移时间与加速时间尺度进行比较，我们发现与合唱波的相互作用确实会导致开放漂移路径上的一部分电子通过Alfven能量。然而，这种加速是否发生得足够快取决于电子居群的能量分布。
Sustained periods of southward interplanetary magnetic field can result in strong magnetospheric convection, during which, the Alfven layer, separating regions of sunward convection and closed drift paths, migrates earthwards. Plasmasheet electrons then have direct access to the inner magnetosphere, traversing the dawn sector before crossing the magnetopause, and present a potential seed population for the radiation belts. Here we examine, for the first time, whether energetic electrons can be sufficiently energised during their drift, via resonant interactions with whistler-mode chorus waves, so as to pass the Alfven layer prior to leaving the system. We utilise a natural coordinate system for magnetosphere convection, (U,B,K) space, in which we calculate the drift trajectories, electron energies on open drift paths, and drift times. The acceleration time from resonant chorus-wave particle interactions is calculated using the Versatile Electron Radiation Belt model (VERB) first as a 2-D diffusion equation and then in 4-D convection-diffusion mode. Comparing the drift times to the acceleration timescales we find that interactions with chorus waves do result in a portion of the electrons on open drift paths passing the Alfven energy. However, whether this acceleration occurs sufficiently quickly depends on the energy distribution of the electron population.