PENGUIn multi-instrument observations of dayside high-latitude injections during the 23 March 2007 substorm

This paper presents ground-based observations from Antarctic stations during a substorm observed on 23 March 2007. Using fluxgate magnetometer data, supported by numerical modeling, the locations of the stations are shown to straddle the open-closed magnetic field boundary. Near these locations (on closed field lines), VLF and riometer signatures are observed to show effects of energetic particle precipitation in the morning sector (extending to the postdawn region), confirmed by observations at geosynchronous orbit. In the VLF data, both the initial injection as well as echoes are observed. The mechanism responsible for such high-latitude injections is thought to be a combination of dynamics of the injection process and drift-shell splitting. Further work will address whether similar observations can be used to infer the dynamics and/or location of the injection region.