Statistical study of the effect of solar wind dynamic pressure fronts on the dayside and nightside ionospheric convection

摘要

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 spaceborne instruments. For a previous case study of an abrupt increase in solar wind dynamic pressure, Super Dual Auroral Radar Network (SuperDARN) measurements of plasma convection within the dayside polar ionosphere revealed an immediate enhancement of plasma convection. The convection enhancement variation closely follows the variation in solar wind pressure. The dayside enhancement was followed by a nightside convection increase about 40 min later, which has similar variation characteristics as seen on the dayside. We now use SuperDARN flow measurements during a large number of solar wind pressure enhancements to conduct a superposed epoch analysis of the effects of solar wind pressure fronts on the dayside and nightside ionospheric convection. The results for the dayside show an increase of convection for nearly all interplanetary magnetic field (IMF) B_z values. The response is more pronounced and immediate (within minutes) for southward IMF, with a duration of 20–30 min. The response time scales increase to 5–10 min for northward IMF, and the enhanced flows last for 30–50 min. We also find a significant enhancement of nightside convection, particularly for small values of IMF B_y, that follows about 10–15 min after the dayside response and can last for 40–50 min.