Evidence against an independent solar wind density driver of the terrestrial ring current

Abstract

The interplanetary electromagnetic fields are generally considered the drivers of the storm‐time terrestrial ring current. Recently, the solar wind density has been advocated as an additional driver. Solar wind density partially determines the density in the plasma sheet, which, in turn, is the likely source for the ring current. Therefore, the solar wind density may drive the ring current by enhancing the ring current source plasma. Some studies, using a few years of data, have found a strong statistical signal for a solar wind density driver with a few hours lag prior to the maximum ring current intensity, as measured by a minimum in Dst. However, we show, using a much larger database of storms, that no consistent role for density alone is evident on time scales of a few hours. The previously reported statistical signal seems to be isolated to a particular interval from November 1994 through September 1995.