Statistical study and corresponding evolution of plasmaspheric plumes under different levels of geomagnetic storms

[摘要] Using observations of Van Allen Probes, we present a statisticalstudy of plasmaspheric plumes in the inner magnetosphere. Plasmasphericplumes tend to occur during the recovery phase of geomagnetic storms.Furthermore, the results imply that the occurrence rate of observedplasmaspheric plume in the inner magnetosphere is larger during strongergeomagnetic activity. This statistical result is different from theobservations of the Cluster satellite with much higher L  shells in mostorbital periods, which suggests that the plasmaspheric plume near themagnetopause tends to be observed during moderate geomagnetic activity (Leeet al., 2016). In the following, the dynamic evolutions of plasmasphericplumes during a moderate geomagnetic storm in February 2013 and a stronggeomagnetic storm in May 2013 are simulated through group test particlesimulation. It is obvious that the plasmaspheric particles drift out on open convection paths due to sunward convection during both geomagnetic storms. It seems that the outer plasmaspheric particles exhaust the energy available to them sooner, and the plasmasphere shrinks faster during strong geomagnetic storms. As a result, the longitudinal width of the plume is narrower, and the plume is limited to lower L  shells during the recovery phase of strong geomagnetic storm. The simulated evolutions may provide a possible interpretation for the occurrence rates: Van Allen Probes tend to observe plumes during stronger geomagnetic storms, and the Cluster satellite with higher L  shells tends to observe plumes during moderate geomagnetic storms.

[学科分类] 化学工程（综合）