STRUCTURE OF THE POLEWARD WALL OF THE TROUGH AND THE INCLINATION OF THE GEOMAGNETIC-FIELD ABOVE THE EISCAT RADAR

A special high-resolution routine of the EISCAT radar has been used to investigate the structure and development of the poleward wall of a d eep trough in electron density. The feature was tracked by the radar d uring a 7-hour period under very quiet geomagnetic conditions. The fie ld-aligned nature of the structure enabled an estimate to be made of t he inclination of the geomagnetic field above EISCAT that was in good agreement with the current model. Observations of narrow field-aligned enhancements in electron temperature demonstrated that the wall of th is trough is a dynamic feature, reforming regularly as the electron de nsity responds on a time scale of tens of minutes to energy input from soft-particle precipitation.