Outer zone relativistic electron acceleration associated with substorm‐enhanced whistler mode chorus
Outer zone relativistic electron acceleration associated with substorm‐enhanced whistler mode chorus
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DOI：
10.1029/2001ja900146
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发表时间：
2002-07
影响因子：
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通讯作者：
N. Meredith;R. Horne;R. Iles;R. Thorne;D. Heynderickx;R. R. Anderson-R.
中科院分区：
文献类型：
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作者：
N. Meredith;R. Horne;R. Iles;R. Thorne;D. Heynderickx;R. R. Anderson-R.
[1]我们给出了来自CRRES卫星的等离子体波和粒子数据，在三个案例研究中，我们研究了局域随机电子加速机制对由哨声模式合唱的共振相互作用驱动的相对论能量的可行性。我们首先考虑一个强地磁风暴，它在其3天的恢复期内包含了长时间的亚暴活动。恢复阶段的特征是以亚相对论能量注入电子，哨声模合唱幅度增强，整个外区相对论电子(E>；1 MeV)的通量逐渐增加，在3.5<；L和4.5区，通量比风暴前水平高一个数量级。接下来，我们考虑一次强地磁风暴，它在3天的恢复期内只有很少的亚暴活动。在这里，恢复阶段的特征是在亚相对论能量下缺乏持续的电子注入，低水平的和声振幅，以及外层相对论电子通量的净减少。最后，我们研究了在没有显著风暴信号的情况下，由DST测量的一段延长的亚风暴活动期。这一时期的特点是亚相对论能量下的电子注入，和声振幅的增强，以及4<；L和6.5区相对论电子通量的逐渐增加。这些结果表明，只有在地磁风暴的主要阶段之后有较长的亚暴活动期时，才能有效地将电子逐渐加速到在天数时间尺度上可见的相对论能量。此外，在没有DST所显示的显著风暴信号的情况下，在长时间的亚暴活动期间，电子可以逐渐加速到相对论能量。个例研究表明，加速机制仅限于等离子体顶以外的区域，并在增强的合唱波存在的情况下发生。这些结果表明，一种局域加速机制，包括通过哨声模式合唱的波-粒子相互作用，将能量在几百keV量级的电子种子粒子群激发到相对论能量，有助于亚暴活动后相对论外区粒子群的改造。
[1] We present plasma wave and particle data from the CRRES satellite during three case studies to investigate the viability of a local stochastic electron acceleration mechanism to relativistic energies driven by resonant interactions with whistler mode chorus. We first consider a strong geomagnetic storm that contains prolonged substorm activity during its 3-day recovery phase. The recovery phase is characterized by electron injections at subrelativistic energies, enhanced whistler mode chorus amplitudes, and a gradual increase in the flux of relativistic electrons (E > 1 MeV) over the entire outer zone, with fluxes exceeding the prestorm level by an order of magnitude in the region 3.5 < L < 4.5. We next consider a strong geomagnetic storm that contains very little substorm activity during its 3-day recovery phase. Here the recovery phase is characterized by a lack of sustained electron injections at subrelativistic energies, a low level of chorus amplitudes, and a net reduction in the flux of relativistic electrons in the outer zone. Finally, we examine a period of prolonged substorm activity in the absence of a significant storm signature, as measured by Dst. This period is characterized by electron injections at subrelativistic energies, enhanced chorus amplitudes, and a gradual increase in the flux of relativistic electrons in the region 4 < L < 6.5. These results suggest that the gradual acceleration of electrons to relativistic energies seen on a timescale of days during geomagnetic storms can be effective only when there are periods of prolonged substorm activity following the main phase of the geomagnetic storm. Furthermore, gradual electron acceleration to relativistic energies can be obtained during periods of prolonged substorm activity in the absence of a significant storm signature as indicated by Dst. The case studies show that the acceleration mechanism is confined to the region outside of the plasmapause and occurs in the presence of enhanced chorus waves. These results suggest that a local acceleration mechanism involving the energization of a seed population of electrons with energies of the order of a few hundred keV to relativistic energies by wave-particle interactions involving whistler mode chorus contributes to the reformation of the relativistic outer zone population following prolonged substorm activity.