Ionospheric-Magnetospheric-Heliospheric Coupling: Storm-Time Thermal Plasma Redistribution

Abstract

Large-scale thermal plasma redistribution phenomena have been observed from the ground and space during the major geomagnetic storms of the recent solar cycle. Plasma redistribution is a multistep, systemwide process involving the equatorial, low, mid, auroral, and polar latitude regions. Penetration electric fields enhance the equatorial ionization anomaly peaks, whereas polarization electric field effects at the dusk terminator redistribute the low-latitude total electron content (TEC) in both longitude and latitude. Magnetic field geometry creates a preferred longitude for the enhancement of low- and mid-latitude TEC in the American sector at sunset. This TEC enhancement forms a localized source for the intense storm enhanced density (SED) erosion plumes that are observed over the Americas during major storms. A second set of storm-time processes leads to the erosion of the plasmasphere boundary layer, transporting the SED plumes to the noontime cusp in the ionosphere and to the dayside magnetopause at high altitudes. Ring current enhancements generate strong poleward-directed subauroral polarization stream (SAPS) electric fields in the evening sector as field-aligned currents close through the low-conductivity ionosphere. The SAPS electric field overlaps the outer plasmasphere, drawing out the SED/plasmasphere erosion plumes. These greatly enhanced fluxes of cold plasma traverse the cusp and enter the polar cap forming the polar tongue of ionization and providing a rich source of heavy ions for the magnetospheric injection and acceleration mechanisms that operate in these regions.