TIME-DEPENDENT CONVECTION AT HIGH-LATITUDES

A fully time-dependent ionospheric convection model, in which electric potentials are derived by an analytic solution of Laplace's equation, is described. This model has been developed to replace the empiricall y derived average convection patterns currently used routinely in the Sheffield/SEL/UCL coupled thermosphere/ionosphere/plasmasphere model ( CTIP) for modelling disturbed periods. Illustrative studies of such pe riods indicate that, for the electric field pulsation periods imposed, longterm averages of parameters such as Joule heating and plasma dens ity have significantly different values in a time-dependent model comp ared to those derived under the same mean conditions in a steady-state model. These differences are indicative of the highly non-linear natu re of the processes involved.