Satellite observations of electric fields in the inner magnetosphere and their effects in the mid-to-low latitude ionosphere

During geomagnetic disturbances, momentum and energy are transferred in significant quantities from interplanetary space to the magnetosphere-ionosphere system through the mediation of charged particles and electric fields. The most dramatic manifestations occur in the plasma sheet and the conjugate auroral ionosphere. However, electric fields observed during magnetic storms also penetrate the inner magnetosphere that maps to subauroral latitudes in the ionosphere. For example, a sudden commencement shock wave initiating the March 1991 magnetic storm created a new radiation belt within minutes. Particle and field measurements by Combined Release and Radiation Effects Satellite (CRRES) near the equatorial plane of the magnetosphere and by Defense Meteorological Satellite Program (DMSP) satellites in the topside ionosphere during the magnetic storm of June 1991 indicate that penetration electric fields energized the stormtime ring current and rapidly transported plasma within subauroral ion drift (SAID) structures at midlatitudes and in upward drafting plasma bubbles at low latitudes. Through enhanced transport or chemical reactions, the SAIDs dug deep plasma troughs at topside altitudes. Equatorial plasma bubbles developed while the ring current was unable to shield the electric field from the innermost magnetosphere.