Dependence of plasma sheet energy fluxes and currents on solar wind-magnetosphere coupling

Abstract

The epsilon solar wind-magnetosphere coupling function was used to estimate the rate at which energy from the solar wind was being dissipated in the inner magnetosphere and ionosphere. The Geotail CPI ion and electron data sets showed that the average percentage of this energy that was carried earthward by energetic particles at |z| < 2.5 RE in the central plasma sheet increased from approximately zero at x = -28 RE to 25% at x = -10 RE when epsilon was high. Much of this increase was attributed to the adiabatic energization of particles as flux tubes collapsed following reconnection events. The Geotail magnetometer and CPI ion data sets also were used to estimate the average electric fields and currents. These parameters provided an alternative viewpoint from which to examine particle energization. The parallel volume current density exhibited a stronger dependence on epsilon than did the perpendicular sheet current density. During disturbed times, a maximum of the parallel current density at a fixed x, y location existed at a distance of ∼3 RE from the neutral sheet. A strong dawn-dusk asymmetry was seen in the long-term averaged region 1 field-aligned currents. The ratio of upgoing dusk side to downgoing dawn side currents at the same x was ∼1.7 throughout the portion of the plasma sheet that could be studied, and was seen during both quiet and disturbed conditions. Previous papers showed that most of this excess upgoing dusk side parallel current was closed through connections to a dusk side downgoing region 0 current system. © 2012. American Geophysical Union. All Rights Reserved.