Ionospheric responses to transient magnetopause reconnection

Abstract

Using both 1-D and 2-D modellng we show that, for low-altitude satellites, a variation in reconnection rate can alter the form of cusp ion signature observed. This behaviour is shown to affect only equatorward-travelling satellites. Modelling of cusp ion dispersions shows the relative invariance of the ionospheric response to reconnection rate variations, provided that the total displacement from equilibrium is constant and that the variations take place on a shorter timescale than the inductive response time. Some applications of a self-consistent numerical implementation of the Cowley-Lockwood (CL) model of ionospheric How excitation are presented. For an example input reconnection rate, the modelled open-closed Geld line boundary motion was consistent with observations of boundary motions during magnetic flux transfer events. The model has been used to calculate ion temperature and to produce a simple CL type expanding flow pattern. We show that the methods used to determine the expansion velocity can be used to discriminate between the two main models for the convection response to a change in reconnection. The CL model is shown to predict both an expanding convection response and a quasi-global convection response. This may provide an explanation for the apparently conflicting observations in the literature.

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