Ionospheric altitude profiles in the main ionospheric trough as observed by field-aligned EISCAT incoherent scatter radar observations

摘要

EISCAT field-aligned observations for winter and equinoctial seasons under quiet geomagnetic conditions were used to study electron concentration Ne(h) distribution in the evening sector of the main ionospheric trough. Both morphological results and physical interpretation are considered. A typical variation of the F2-layer maximum height is hmF2 increase in the trough minimum followed by hmF2 sharp decrease in the polar wall of the trough and in the auroral oval. The effective scale height H_(eff) of plasma distribution in the topside F2-region increases in the trough minimum. Specific Ne(h) profiles with H_(eff) decreasing with height observed in the trough minimum are due to upward flow of plasma from the F2-region. Such Ne(h) distributions are associated with narrow deep troughs, but only if the trough is formed in non-sunlit conditions.