Phase space holes, double layers and other solitary electric field structures, referred to as time domain structures (TDSs), often occur around dipolarization fronts in the Earth's inner magnetosphere. They are considered to be important because of their role in the dissipation of the injection energy and their potential for significant particle scattering and acceleration. Kinetic Alfvén waves are observed to be excited during energetic particle injections, and are typically present in conjunction with TDS observations. Despite the availability of a large number of spacecraft observations, the origin of TDSs and their relation to kinetic Alfvén waves remains poorly understood to date. Part of the difficulty arises from the vast scale separations between kinetic Alfvén waves and TDSs. Here, we demonstrate that TDSs can be excited by electrons in nonlinear Landau resonance with kinetic Alfvén waves. These electrons get trapped by the parallel electric field of kinetic Alfvén waves, form localized beam distributions, and subsequently generate TDSs through beam instabilities. A big picture emerges as follows: macroscale dipolarization fronts first transfer the ion flow (kinetic) energy to kinetic Alfvén waves at intermediate scale, which further channel the energy to TDSs at the microscale and eventually deposit the energy to the thermal electrons in the form of heating. In this way, the ion flow energy associated with dipolarization fronts is effectively dissipated in a cascade from large to small scales in the inner magnetosphere.

中文翻译：

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动力学Alfvén波与热电子之间的非线性Landau共振相互作用：时域结构的激发

相空间空穴，双层和其他孤立电场结构（称为时域结构（TDS））通常出现在地球内部磁层的双极化前沿附近。它们被认为是重要的，因为它们在耗散注入能量中具有重要作用，并且具有显着的粒子散射和加速的潜力。动力学Alfvén波被观察到在高能粒子注入过程中被激发，并且通常与TDS观测一起出现。尽管有大量航天器观测资料可供使用，但迄今为止，对TDS的起源及其与动力学Alfvén波的关系仍然知之甚少。部分困难来自动力学Alfvén波与TDS之间的大规模分离。这里，我们证明了TDSs可以被非线性Landau共振的Alfvén动力学波中的电子激发。这些电子被动态Alfvén波的平行电场捕获，形成局部电子束分布，然后通过电子束不稳定性产生TDS。出现如下图所示：宏观双极化前沿首先将离子流（动能）传递给中尺度的动能Alfvén波，这进一步将能量以微尺度传递给TDS，并最终以电子形式将能量沉积到热电子中。加热。以此方式，与双极化前沿相关的离子流能量在内部磁层中从大到小依次级联有效地耗散。这些电子被动态Alfvén波的平行电场捕获，形成局部电子束分布，然后通过电子束不稳定性产生TDS。出现如下图所示：宏观双极化前沿首先将离子流（动能）传递给中尺度的动能Alfvén波，这进一步将能量以微尺度传递给TDS，并最终以电子形式将能量沉积到热电子中。加热。以此方式，与双极化前沿相关的离子流能量在内部磁层中从大到小依次级联有效地耗散。这些电子被动态Alfvén波的平行电场捕获，形成局部电子束分布，然后通过电子束不稳定性产生TDS。出现如下图所示：宏观双极化前沿首先将离子流（动能）传递给中尺度的动能Alfvén波，这进一步将能量以微尺度传递给TDS，并最终以电子形式将能量沉积到热电子中。加热。以此方式，与双极化前沿相关的离子流能量在内部磁层中从大到小依次级联有效地耗散。宏观上的双极化前沿首先将离子流（动能）能量转移到中等规模的动能Alfvén波上，这进一步将能量引导至微尺度上的TDS，并最终以加热的形式将能量沉积到热电子上。以此方式，与双极化前沿相关的离子流能量在内部磁层中从大到小依次级联有效地耗散。宏观上的双极化前沿首先将离子流（动能）能量转移到中等规模的动能Alfvén波上，这进一步将能量引导至微尺度上的TDS，并最终以加热的形式将能量沉积到热电子上。以此方式，与双极化前沿相关的离子流能量在内部磁层中从大到小依次级联有效地耗散。