Propagation characteristics of plasma sheet oscillations during a small storm

Abstract

On 24 March 2007, the THEMIS spacecraft were in a string‐of‐pearls configuration through the dusk plasma sheet at the recovery phase of a small storm. Large undulations of the plasma sheet were observed that brought the five probes from one lobe to another. Each neutral sheet crossing was accompanied by bursty bulk flows and Pi2 oscillations. In this paper we focus on the low frequency (∼10 min) large scale plasma sheet undulations and determine their propagation characteristics, origin, and properties in the presence of storm‐time substorms. As the first case of “flapping waves” observed and analyzed during storm‐time, it is interesting to find their characteristics coincide with those described by previous quiet‐time observations. These characteristics include flankward propagation of the undulations with velocities generally between ∼40–130 km/s.