The magnetospheric cleft-Ionospheric effects

Abstract

The fluxes of electrons that precipitate through the day side clefts of the magnetosphere are intense enough and deposit their energy at a high enough altitude to heat and ionize the F layer and top side ionosphere substantially. Relevant synoptic results from bottom side and top side sounder measurements are reviewed, and new data from the Isis satellites are presented. The effects of precipitation through the cleft can be seen in bottom side ionograms, but the diurnal variations that appear in routine monthly median plots are probably due primarily to other effects. As seen from above the F layer by the top side sounders on Alouette and Isis spacecraft, the most obvious effects are an expansion (increase in scale height) of the top side ionosphere due to heating and the presence of small-scale spatial fluctuations in density. The electron density at the F layer peak is often, but not always, increased. The increased electron density at satellite altitudes associated with top side expansion is often seen at a slightly higher latitude than the precipitation, and this displacement in latitude (of ∼1°) is interpreted in terms of an antisunward drift due to magnetospheric convection.