Abstract
Abstract. Using observations of Van Allen Probes, we present a statistical study of plasmaspheric plumes in the inner magnetosphere. Plasmaspheric plumes tend to occur during the recovery phase of geomagnetic storms. Furthermore, the results imply that the occurrence rate of observed plasmaspheric plume in the inner magnetosphere is larger during stronger geomagnetic activity. This statistical result is different from the observations of the Cluster satellite with much higher L shells in most orbital periods, which suggests that the plasmaspheric plume near the magnetopause tends to be observed during moderate geomagnetic activity (Lee et al., 2016). In the following, the dynamic evolutions of plasmaspheric plumes during a moderate geomagnetic storm in February 2013 and a strong geomagnetic storm in May 2013 are simulated through group test particle simulation. 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.
Highlights
The southward interplanetary magnetic field (IMF) at the magnetopause brings about dayside magnetopause reconnection, resulting in an increase in dawn–dusk convection electric fields in the inner magnetosphere (Dungey, 1961)
The results imply that the occurrence rate of plasmaspheric plumes in the inner magnetosphere is largest during strongest geomagnetic activity, which is different from the statistical result near the magnetopause provided by Lee et al (2016)
To explain the disparity in the occurrence rates of the observed plasmaspheric plume associated with geomagnetic activity levels in different L shells (L ≤ 6.2 in the inner magnetosphere observed by Van Allen Probe A satellite and L ≥ 6.2 during most of the Cluster orbital period), we run group test particle simulations to analyze the evolution of plasmaspheric plumes during different levels of geomagnetic storms
Summary
The innermost magnetosphere is occupied by a torus of cold dense plasma known as the plasmasphere (Lemaire et al, 1998). Under the effect of a dawn–dusk convection electric field, plasmaspheric particles move sunward through the E × B drift and may transfer into the magnetospheric boundary layers This dynamic mechanism leads to the erosion of the plasmasphere and the formation of a plasmaspheric plume near the dusk side (Goldstein et al, 2004; Darrouzet et al, 2008; Walsh et al, 2013). After the time interval of the geomagnetic disturbance, low-energy ionospheric particles are drawn upward from low altitudes along magnetic field lines and contribute to the refilling of the eroded plasmasphere It may take more than 10 d to recover to the normal level of the plasmasphere (Chu et al, 2017; Lointier et al, 2013). The results imply that the occurrence rate of plasmaspheric plumes in the inner magnetosphere is largest during strongest geomagnetic activity, which is different from the statistical result near the magnetopause provided by Lee et al (2016). To explain the different occurrence rates of observed plasmaspheric plumes as a function of the levels of geomagnetic activity, group test particle simulations are used to exhibit the evolution of plasmaspheric plumes during both moderate and strong geomagnetic activity
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
