Simultaneous F-region conjugate point dawn effects at two mid-latitude stations

Abstract

Observations of F-region electron temperature ( T e ) and concentration ( N e ) made simultaneously by incoherent scatter radars at St. Santin (44·6°N, 2·2°E) and Malvern (52·1°N, 2·3°W) during a period covering conjugate point and local dawns on 29 January 1969 are presented. The rate of rise and the maximum value of T e are greater at Malvern than at St. Santin, and a series of changes in N e and h m F2, the same for both stations, is clearly initiated by the onset of conjugate point heating. It is shown that the initial effects are due to a heat flux from the exosphere, approximately the same at both stations. A simple model is developed, following the arguments of a previous paper (Bauer et al., 1970), that shows that the temperature differences are due to differences in local N e . A discussion of the changes in N e and h m F2 shows that an enhanced diffusion rate and a plasma flux from the exosphere are both dominant at times, but that enhancement of the electron loss rate is probably not important.