Variation of plasmapause location during magnetic storms

Abstract:

This paper investigates the dynamic evolutions of the plasmapause during magnetic storms based on in situ observations and empirical modeling results. Superposed epoch analysis is performed on the plasmapause location identified from THEMIS in situ measurements during the 61 magnetic storms from 2009 to 2013. The evolution of the plasmapause is generally consistent with the theory of erosion/refilling of the plasmapause. From multi-spacecraft in situ measurements, we are able to directly calculate the plasmapause radial velocity, V_pp. It is found that the radial velocity is on average earthward during main phase and turns outward during recovery phase. The empirical plasmapause model by Liu et al. [2015] is further utilized to reproduce the plasmapause location during these 61 storms to reveal the details of the evolution, such as the local time dependence. It is shown that the expansion of the plasmapause starts firstly on the midnight sector at t₀+1hr, and subsequently on the dawnside at t₀+4hr, dayside at t₀+8hr and duskside at t₀+11hr, where t₀ corresponds to the time of Dst minimum. The averaged V_pp is quantified based on modeling results as up to 0.17 R_E/hr earthward in the main phase and 0.08 R_E/hr outward in the recovery phase. The knowledge of the dynamic evolution of plasmapause provided in this paper is valuable to understand the dynamics of the inner magnetosphere during magnetic storms