内磁层中电磁离子回旋波的分布及其激发机制的研究

Electromagnetic Ion Cyclotron (EMIC) waves play an important role in the dynamic evolution of the inner magnetosphere. Through wave particle interactions, EMIC waves can precipitate ring current ions and relativistic electrons, even can heat cold electrons. Therefore, it is important to study the distribution characteristics and the generation mechanism of EMIC waves in the inner magnetosphere. Some previous studies also focus on the same topic, but the shortcoming of their researches is that the satellites whose data they utilized spent limit time in the inner magnetosphere and the frequency resolution of the magnetometer data were not high enough. The orbits of the Van Allen Probes keep in the inner magnetosphere and the data of their magnetometer has enough high frequency resolution. This project will utilize the data from Van Allen Probes to analyze EMIC waves in the inner magnetosphere, both about their distribution characteristics and their generation mechanisms. The distribution characteristics of the EMIC wave's polarization feachure, amplitude and their resonance energy with energetic particles will be researched. On the other hand, the relation between EMIC wave distribution characteristics and the solar wind dynamic pressure, the geomagneic condition, the density of the plasma will be checked.This project will also utilize the particle data from the Van Allen Probes to study the generation mechanism of EMIC waves which lead to the distribution characteristics of them. This research will be helpful to establish the model of inner magnetosphere and space weather focusting.

电磁离子回旋波在内磁层的动力学演变中扮演着非常重要的角色，通过波粒相互作用，它可以沉降环电流离子和辐射带电子，甚至可以加热冷电子。因此，研究电磁离子回旋波在内磁层中的分布和产生机制就显得尤为重要。对于电磁离子回旋波的统计，前人也有一定的工作基础，但是他们的研究受到了卫星在内磁层中运行时间较短或磁场仪器采样率不高的限制。范阿伦辐射带卫星的轨道一直保持在内磁层而且磁场数据具有足够高的采样率。本项目拟利用辐射带卫星远地点绕地球一周这段时间内的磁场数据，对电磁离子回旋波在地球内磁层中的分布做一个比较详尽的研究，得出不同波段的电磁离子回旋波的极化特性、波动幅度、与能量离子的共振能量等特征随着L值以及磁地方时的分布，以及这种分布与太阳风动压条件、地磁扰动情况、等离子体密度的关系；同时结合高能粒子的分布揭示电磁离子回旋波的产生机制。研究成果将为内磁层的理论建模及空间天气预报提供重要的依据。

本项目研究了电磁离子回旋波在内磁层中的分布特征，这种分布特征与地磁活动、太阳风动压、冷等离子体层的关系，以及对辐射带超相对论电子的影响，发现了电磁离子回旋波的L值覆盖范围可以比较宽，改变了以往对于电磁离子回旋波L范围覆盖比较窄的认识，揭示了来自于太阳风的二价氦离子在环电流中存在的可能性以及对电磁离子回旋波激发的影响。通过分析范阿伦探针卫星远地点环绕地球一周（接近两年）的数据，我们分析了电磁离子回旋波的分布随着地磁活动的变化，计算得到了电磁离子回旋波在不同地磁活动情况下的出现率，发现了电磁离子回旋波的分布随着地磁活动的变化与等离子体层随着地磁活动的变化相吻合，揭示了冷等离子体层在电磁离子回旋波激发中起的作用。