Nightside flow enhancement associated with solar wind dynamic pressure driven reconnection

[1] Over the past few years the prominent role of solar wind dynamic pressure in enhancing dayside and nightside reconnection and driving enhanced ionospheric convection has been documented by both ground and spaceborn instruments. Super Dual Auroral Radar Network (SuperDARN) observations show that solar wind pressure fronts induce significantly enhanced ionospheric convection in the dayside ionosphere. In parallel, Defense Meteorological Satellite Program (DMSP) precipitating particle measurements and POLAR Ultra-Violet Imager (UVI) images have demonstrated that sudden solar wind pressure increases also significantly reduce the size of the polar cap, especially on the nightside, suggesting an enhancement of magnetotail reconnection. MHD models of the interaction of the magnetosphere with solar wind pressure fronts have reproduced the enhancement of dayside reconnection but have failed so far to account for the observed closing of the polar cap on the nightside and the suggested magnetotail reconnection increase. We use SuperDARN measurements of ionospheric convection within the nightside polar ionosphere, including near the magnetic separatrix, to evaluate the strength of the observed nightside reconnection enhancement after an abrupt increase in solar wind dynamic pressure on 6 November 2000 and compare it with similar observations on the dayside. We show that an enhancement of nightside convection occurs after a sudden increase in solar wind pressure, delayed by about 40 min compared with the observed dayside convection enhancement. The nightside enhanced flows are observed crossing the open-closed boundary determined by POLAR UVI data, indicating an enhancement of tail reconnection that is possibly due to the pressure increase and is, in addition to the tail reconnection, associated with the more immediate closing of the polar cap.