Equatorial Magnetosonic Waves Observed by Cluster Satellites: The Chirikov Resonance Overlap Criterion
Equatorial Magnetosonic Waves Observed by Cluster Satellites: The Chirikov Resonance Overlap Criterion
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DOI：
10.1029/2019ja026680
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发表时间：
2019-04
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影响因子：
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通讯作者：
Homayon Aryan;S. Walker;M. Balikhin;K. Yearby
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作者：
Homayon Aryan;S. Walker;M. Balikhin;K. Yearby
磁声波在相对论辐射带电子的整体动力学中起着重要的作用。模拟辐射带演化的数值代码通常会考虑磁声波的波粒相互作用。在这些代码中的扩散系数纳入这些波的发生和振幅的统计调查的结果的基础上，一般估计。这些统计模型假设磁声波的频谱在频率空间上是连续的。只有当波的离散性质满足奇里科夫重叠准则时，这个假设才有效。否则，连续频谱的假设可能会在波动模型中产生错误的结果，从而导致对内磁层数值模型中使用的电子扩散系数的估计。最近，它被证明，通过一个案例研究中进行的一个单一的短（10秒）周期快照在一个较长的波事件，赤道磁声波的离散性质满足奇里科夫重叠标准，因此连续频谱的假设是有效的扩散系数的计算。本文将这一研究扩展到一个更广泛的时间范围内，许多磁声波事件，以确定波的离散性质是否总是满足奇里科夫重叠准则。结果表明，大多数，但不是全部，离散磁声发射满足奇里科夫重叠准则。因此，在拟线性理论中使用连续谱可能并不总是合理的。
Magnetosonic waves play an important role on the overall dynamics of relativistic radiation belt electrons. Numerical codes modeling the evolution of the radiation belts often account for wave‐particle interaction with magnetosonic waves. The diffusion coefficients incorporated in these codes are generally estimated based on the results of statistical surveys of the occurrence and amplitude of these waves. These statistical models assume that the spectrum of the magnetosonic waves can be considered as continuous in frequency space. This assumption can only be valid if the discrete nature of the waves satisfy the Chirikov overlap criterion. Otherwise, the assumption of a continuous frequency spectrum could produce erroneous results in wave models and hence estimates of the electron diffusion coefficients used in numerical models of the inner magnetosphere. Recently, it was demonstrated, through a case study conducted on a single short (10 s) period snapshot within a longer wave event, that the discrete nature of the equatorial magnetosonic waves do satisfy the Chirikov overlap criterion and so the assumption of a continuous frequency spectrum is valid for the calculation of diffusion coefficients. This paper expands this study to a broader range of time with many magnetosonic wave events to determine whether the discrete nature of the waves always satisfy the Chirikov overlap criterion. The results show that most, but not all, discrete magnetosonic emissions satisfy the Chirikov overlap criterion. Therefore, the use of the continuous spectrum, employed in quasi‐linear theory, may not always be justified.