Local Time Variations of Ionospheric F Layer Radial Current in Response to Enhanced Solar Wind Input

Using Challenging Minisatellite Payload and the Republic of China Satellite-1 observations, the response of ionospheric radial current (IRC) in the F region to the enhancement of merging electric field (Em) at different magnetic local times (MLT) is investigated. Possible physical mechanisms are discussed in terms of neutral wind, conductivity, and prompt penetration electric field (PPEF). The disturbance IRC (Delta IRC) increases in the upward (downward) direction in the daytime (nighttime) within 3 hr after Em enhancement. However, disturbance zonal winds increase westward (eastward) at 12-18 MLT (00-06 MLT). The reduced F region electron density may help weaken IRC at 06-12 MLT and 18-24 MLT. This work indicates that the daytime eastward (nighttime westward) PPEF drives equatorward (poleward) Hall current (JH) at low latitudes, resulting in both upward (downward) Delta IRC and eastward (westward) plasma drift at the F region magnetic equator. The ionospheric radial current (IRC) flows vertically in the ionospheric F region near the magnetic equator, which plays an important role in the coupling process of E and F layers in the ionosphere. IRC is generally considered to be controlled by local neutral wind. The impact of solar wind electric field on IRC is still unknown. Previous studies have reported penetration of the high-latitude electric field to the equatorial ionosphere. For the first time, we show that a sudden increase in the solar wind merging electric field leads to drastic changes in IRC in the F layer. The local time differences in the IRC changes could be explained by the penetration electric field effect rather than the neutral wind effect. During Em enhancement, F layer radial current increases upward (downward), and plasma accelerates eastward (westward) at day (night)Local time differences in both radial current and plasma zonal drift are due to penetration electric field rather than F layer neutral windThe weakening of F layer radial current at 06-12 magnetic local times (MLT) and 18-24 MLT could be partly induced by the decrease in F layer electron density