等离子体层嘶声散射辐射带电子的损失时间尺度建模研究

等离子体层嘶声(Plasmaspheric hiss)是地球辐射带中的一种常见哨声模波动，主要存在于等离子体层中.嘶声波可以通过回旋共振散射辐射带电子，在辐射带槽区的形成过程和反转能谱的演化过程中具有重要作用.因此，在辐射带动态建模中需要考虑嘶声波的作用，常用的方法是在辐射带电子扩散方程中加入嘶声波导致的损失项，用损失时间尺度(loss timescale)代表电子损失的快慢.本文基于等离子体层嘶声对辐射带电子的投掷角散射系数模型计算了嘶声波导致辐射带电子损失的时间尺度.建立了包含L(范围为3~6)、冷等离子体参数α^*(范围为3~30)以及电子能量(范围为1 keV~10 MeV)的电子损失时间尺度参数化模型.基于该模型，可以快速计算电子在嘶声波散射效应下的损失时间尺度.通过与卫星实际观测的电子损失时间尺度对比，验证了本文建立的嘶声波损失时间尺度模型的合理性，可为实现辐射带的快速建模提供有利支持.

Simulations of radiation belt electron loss timescales due to scattering by plasmaspheric hiss

Plasmaspheric hiss is a common whistle wave mode in the Earth's radiation belts, predominantly present in the plasmasphere. Hiss waves can scatter radiation belt electrons in terms of the process of cyclotron resonance, and play an important role in the formation of the radiation belt slot region and in the evolution of the reversed electron energy spectrum. Therefore, the contributions of hiss waves need to be considered in detail when modeling the radiation belt electron dynamical evolution. A common approach is to incorporate the hiss-induced electron scattering effect as an empirical loss term in numerical simulations. The loss timescale is used to represent the rapidity of electron loss. In this paper, the loss timescales of radiation belt electrons due to scattering by hiss waves are calculated based on a reasonable matrix of hiss-driven electron pitch angle diffusion coefficients, which covers a broad parametric space, i.e., L=3~6, the cold plasma parameter α* of 3~30, and the electron energy of 1 keV~10 MeV. We further develop a prameterized model of hiss-induced electron loss timescale as a function of L-shell, α* and electron energy. Based on this model, the electron loss timescale caused by hiss wave scattering can be quickly evaluated under various conditions. By comparing quantatively the modelled electron loss timescales with those observed by the Van Allen Probes in the plasmasphere, we find good consistency between the model and the observations. Therefore, the reliability of the established parameterization model of electron loss timescales is well verified, which can provide valuable support for efficient simulations of radiation belt electron variations.