Plasmasphere electron temperature structures

Inspection of electron temperature (T _e ) profiles obtained by the thermal electron detector instrument along 5676 individual orbits of the Akebono satellite reveal the existence of localized structures with a latitude extent of 1-3θ. The analysis was constrained to the range 2 < L < 3.2 in the northern hemisphere within the period 1991-1997. Eighty-seven well-defined structures were selected, containing a marked increase of T _e at least 20% above the background level. The electron density (N _e ) and the wave intensity at the upper hybrid resonance frequency, recorded by the plasma wave and sounder instrument on the same satellite, were also used in the analysis. It was found that N _e troughs and an increase of the electrostatic electron cyclotron harmonic waves perfectly co-located with the T _e structures. The structures were observed at altitudes above 3000 km, as 70% of them are found between 03 and 08 h magnetic local time. While the plasma inside the structures is always warmer, the plasma pressure can be either higher or lower than outside.