Equatorial ionospheric electrodynamics associated with high‐speed solar wind streams during January–April 2007

Abstract

High‐speed solar wind streams cause recurrent geomagnetic activity and ionospheric disturbances. In this study, we analyze the equatorial ionospheric ion drift measured by the Defense Meteorological Satellite Program (DMSP) satellites near dusk when high‐speed solar wind streams with a period of 13.5 days occurred during January–April 2007. A well‐defined quantitative correlation between the solar wind velocity and the equatorial ionospheric ion drift is identified for the first time. The plasma drift in the dusk equatorial ionosphere induced by high‐speed solar wind streams is eastward in the zonal direction and downward in the vertical direction at the altitude of DMSP orbit (∼840 km) during this low solar activity period (January–April 2007). The zonal component of the equatorial ionospheric ion drift is inversely correlated with the vertical component. The ionospheric ion zonal drift varies, on average, from −40 to 40 m s−1 when the solar wind velocity varies from 300 to 700 km s−1 over a 13.5 day period, and the ion vertical drift varies from 10 to −10 m s−1. The quantitative correlations between the solar wind velocity and ionospheric ion drift and between the vertical and zonal components of the ion drift velocity are important for understanding the equatorial ionospheric electrodynamics associated with high‐speed solar wind streams and for space weather prediction.