磁暴期间环电流离子成分变化的来源研究

The ion composition in the ring current will change remarkably during the magnetic storm. The oxygen ions contribution to the ring current relative to the protons will increase during magnetic storms. Studies have shown that the several mechanisms such as the non-adiabatic acceleration, the wave-particle interaction, and the ionospheric ion outflow can account for the ion composition variation in the ring current during the magnetic storm. However, which mechanism is more important, the exact region where the variation is happened is still under debate.. In this project, joint observations from Van Allen Probes in the inner magnetosphere, MMS and Cluster in the near-Earth plasma sheet will be used to study the how the ion composition variation happen. By comparing the difference of the acceleration processes in the inner magnetosphere and the near-Earth plasma sheet, we try to investigate the contribution of different acceleration mechanism to the increase of the O+/H+ energy density ratio. This project will help us to understand the injection processes of different ions and the role of the oxygen ions in the ring current formation and also provide the important information for the storm-substorm relationship.

环电流离子组成成分在磁暴期间会发生显著变化，主要表现为氧离子对环电流的贡献相对于氢离子显著增强。已有的研究表明：两种离子在非绝热加速，波粒相互作用，电离层离子上行等物理过程中的差异均能够使离子成分发生变化，然而，变化发生的区域（环电流局地发生还是磁尾等离子体片区域形成然后注入至环电流区域）目前存在较大争议，何种机制占主要贡献仍然有待进一步研究。. 本项目拟利用Van Allen Probes卫星在内磁层和Cluster，MMS卫星在近磁尾等离子体片的联合观测，通过个例、统计及理论分析，深入研究磁暴期间环电流离子成分变化的根本成因，重点研究磁暴演化过程中两种离子在磁尾等离子体片及内磁层区域加速过程的异同，以及对环电流离子成分变化的贡献大小。项目的实施将有利于进一步理解磁尾等离子体片中不同离子向内磁层的注入机制以及氧离子在环电流形成过程中的作用，为揭示磁暴与亚暴的关系提供重要的参考信息。