多频段EMIC波共振散射辐射带相对论电子的损失时间尺度研究

Study on the scattering loss timescales induced by multi-band EMIC waves on radiation belts relativistic electrons

作为地球磁层中一种分布广泛的电磁波,电磁离子回旋波(Electromagnetic ion cyclotron waves,简称EMIC波)是地球辐射带相对论电子的重要损失机制.EMIC波通常呈现H+、He+和O+三种不同频段,不同频段对相对论电子的散射效应和损失时间尺度大不相同.准线性理论是定量分析不同频段EMIC波对地球辐射带相对论电子散射效应的重要工具,我们利用基于准线性理论开发的Full Diffusion Code(FDC),分别计算了H^(+)、He^(+)、O^(+)三种频段EMIC波在不同空间范围、背景等离子体条件以及不同传播角模型下对辐射带相对论电子的弹跳平均投掷角散射系数,建立了L=1.5~7,背景等离子体参数α*(=f_(pe)/f_(ce))=6~30范围内的多频段EMIC波电子散射系数矩阵库.进而,我们计算了辐射带相对论电子在不同频段EMIC波散射作用下的损失时间尺度,获得了在不同磁层条件下EMIC波损失沉降相对论电子的定量信息.这些结果对于提升地球辐射带动力学过程建模水平、开展辐射带空间天气预报具有重要价值.

As a widely distributed electromagnetic wave in the Earth's magnetosphere,electromagnetic ion cyclotron(EMIC)waves play an important role in the loss of relativistic electrons in the Earth's radiation belts.EMIC waves usually occur in three distinct emission bands(H+,He+and O+),which have different scattering effects and result in different loss timescales for relativistic electrons.Quasi-linear theory is an important tool for quantitative analysis of relativistic electron scattering effects of different emission bands EMIC waves on the radiation belt relativistic electrons.We use the Full Diffusion Code(FDC)based on the quasi-linear theory to calculate the bounce-averaged pitch angle scattering coefficients of H^(+),He^(+)and O^(+)band EMIC waves.Based on the calculation results of scattering coefficients in different spatial ranges,background plasma conditions and wave normal angle distributions,we establish the scattering coefficient matrix library with L=1.5~7,background plasma parametersα*(=f_(pe)/f_(ce))=6 to 30 for multi-band EMIC waves.Furthermore,we calculate the loss timescales of relativistic electrons induced by different emission band EMIC waves,which can obtain the quantitative information of relativistic electrons loss and precipitate in different magnetospheric conditions.These results are very helpful to improve the kinetic modeling and space weather forecast of the Earth's radiation belts.