Plasmaspheric Depletion and Refilling after Geomagnetic Storms in the Dynamic Model of the Plasmasphere

Abstract:

The three-dimensional physical dynamic kinetic model of the plasmasphere is a physics-based model partially constrained by empirical observations and available for running on the space weather portal. The position of the plasmapause is determined by the interchange instability mechanism. The level of geomagnetic activity driven by the Kp index determines the convection electric field which dominates at large radial distances. During storm and substorm events, the convection rate increases, especially in the postmidnight MLT sector. This leads to an inward motion of the plasmapause in this MLT sector during the storms and a depletion of the outer flux tubes. The combination with the corotation electric field leads later to the formation of a plume in the afternoon sector which then rotates with the Earth. After geomagnetic storms, progressive refilling process takes several days to increase the density in the depleted flux tubes located in regions between the vestigial plasmapause and the new plasmapause situated at larger radial distance. The model is coupled with an empirical model of the ionosphere which determines the boundary conditions at low altitudes. Like in other kinetic models of planetary and stellar atmospheres, the density, flux, velocity and temperatures of the particles are obtained by solving the kinetic evolution equation to determine the velocity distribution function of the particles. Additional new results are related to the consideration of the plasmaspheric wind appearing during low activity periods. Comparisons with IMAGE and CLUSTER observations show good agreement with the results of the model, including during periods when a plume is visible during several successive days.