Consequences of a saturated convection electric field on the ring current

[1] Results from kinetic simulations of hot ion transport in the inner magnetosphere are used to show that the ring current energy content must have a nonlinear (asymptotic) coupling relationship to extreme solar wind conditions due to saturation of the near-Earth convection electric field E-y,E-conv (defined as a function of cross polar cap potential DeltaPhi(PC)). This study examines the Bastille Day magnetic storm (July 14-17, 2000), where the z-component of the interplanetary magnetic field reached -58 nT and the solar wind speed exceeded 1100 km s(-1). A large discrepancy in the modeled DeltaPhi(PC) confirms a nonlinear response of the high-latitude potential during this event. It is found that this nonlinearity of E-y,E-conv is necessary to obtain reasonable agreement between the simulation results and the observed geoeffectiveness (Dst) of the storm.