Fast Plasma Drifts in the High Latitude Ionosphere

Abstract

AbstractWe have identified over 200 fast plasma drift events (>5 km/s) in the high‐latitude ionosphere, as measured by the electric field double probe on the Dynamics Explorer‐2 satellite during its 18 months lifetime from August 1981 to February 1983. Although these drifts can appear at all local time sectors, they are most common on the dawnside and in the pre‐midnight sector. The fast plasma drifts generally occur between 64° and 82° inv.lat. although they sometimes appear below 55° inv.lat. in the pre‐midnight sector, in which case they appear associated with a phenomenon often referred to as sub‐auroral ion drifts. For increasing Auroral Electrojet index, their occurrence rate increases and their latitudinal locations move equatorward. The observed events last between 0.1 and 60 s, corresponding to (north‐south) widths of 1–500 km along the satellite trajectory. The observations show a seasonal dependence such that the faster drifts tend to occur over the dark (winter) hemisphere.