The influence of convection on the structure of the high-latitude ionosphere

Fundamental to the understanding of high-latitude ionospheric behaviour is an appreciation of the convection electric field and its consequences. This electric field drives a number of processes which directly influence the plasma, including vertical ion drifts, Joule heating and enhanced neutral air velocities. Particle precipitation regions are closely connected with convection boundaries. Universal time variations can, in many cases, be directly related to the diurnal variation of the convection electric field in the geographical frame. Convection also has a profound influence on the interpretation of observations, because understanding why plasma densities have their observed characteristics requires knowledge of the past history of the observed plasma. This past history is determined by the convection electric field, as it transports plasma between regions of differing dominant plasma processes. Where reasonable estimates of the convection electric field exist, numerical models of the ionosphere seem capable of reproducing the characteristics of observed plasma behaviour. This is demonstrated by using the European incoherent-scatter facility's observations for days for which such estimates are available. (author)