Response of Earth's Ionosphere to Interplanetary Shocks

Abstract

AbstractThis paper presents three‐dimensional, global numerical simulations of the dynamic response of the Earth's ionosphere to interplanetary shocks. The background interplanetary magnetic field is spiral with a vanishing south‐north component, the initial ionosphere is dominated by the region I field‐aligned current (FAC) and the corresponding dawn‐dusk electric field, and the interplanetary shock collides with the Earth along the Sun‐Earth line. It is shown that with the impact of interplanetary shocks, the region I current moves towards the midnight sector, accompanied by a successive occurrence of two FAC structures: an anomalous FAC pair of opposite direction to the region I current and a new region I current of the same direction. The anomalous FAC pair creates a transient dusk‐dawn electric field over the polar cap, tailing behind the original region I current and drifting towards the night side until it falls into oblivion. In the meantime, the new region I current keeps increasing and expanding towards the night and equator side, and it eventually replaces the original region I current, so the polar cap returns to a state similar to the original with a dawn‐dusk electric field. Such a response depends on the strength of the interplanetary shock. For a stronger shock, the new region I current gets stronger, extends for a longer distance towards the equator, and reaches a lower latitude. These results agree with the observations associated with traveling convection vortices and midday sub‐auroral patches.