Abstract
Observations of F-region plasma densities and temperatures made with the pulsed incoherent scatter radar at Malvern (52.1°N, 2.3°W) during six equinox and winter nights between October 1968 and October 1970 are presented. Two separate periods of apparent influx of plasma can be distinguished, one before and one after magnetic conjugate point (MCP) sunrise. The first influx period was seen on five nights and the second on two nights. In all except one case, hydrostatic equilibrium appears to have been preserved within the errors of measurement. By comparing the observed heat input to the electron gas with that expected if the apparent flux is due to in situ ionisation by precipitating 200 eV electrons, it is found that for some periods part of the flux could be due to precipitation, but in other cases an influx of thermal plasma must be occurring. The equivalent vertical drift velocities required at great heights to produce the observed fluxes by diffusion from the exosphere seem anomalously large, especially for the post-MCP flux. It is suggested that when a plasma flux occurs, north-south horizontal transport caused by an east-west electric field is at least as probable a source as vertical transport by diffusion.
Published Version
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