Source processes in the high-latitude ionosphere

Abstract

This chapter deals with the sources of magnetospheric plasma within the high latitude ionosphere. This source of plasma for the magnetosphere was perhaps first discussed by Dessler and Hanson (1961), who recognised that the terrestrial ionosphere is a large potential source of plasma, especially light ions at high latitudes outside the plasmasphere. There the flux tubes do not fill up to diffusive equilibrium, suggesting a sink of outflowing plasma into the downstream solar wind. Dessler and Michel (1966) extended this theme, exploring the formation of a steady polar ionospheric outflow into the magnetosphere. They adopted an approach similar to that used by Chamberlain to describe the solar wind, and suggested a subsonic evaporative process. Banks and Holzer (1969a) adopted an approach more like the one that Parker (1958) had taken to the solar wind, and the competition of these ideas recapitulated much of the earlier debate concerning the nature of the solar wind.