The solar wind influences plasmasphere electron content

Abstract

Magnetospheric plasma convection has been reviewed in detail by Axford. A viscous-like interaction between plasma and magnetic field and magnetic-field-line merging have been suggested as mechanisms producing magnetospheric convection. In either model, convection is sustained by a dawn-dusk electric field (E_conv) which has been shownto depend on solar-wind speed V_sw. Vasyliunas suggested a linear dependence, but Mendillo and Papagiannis estimated that the convection electric field varies nearly quadratically with solar wind speed-this conclusion was supported by Kivelson. The convection field E_conv and hence solar wind speed have important roles in determining the location of plasmaspause. Model calculations assuming enhancement of the solar wind showed the plasmapause everywhere to be located at smaller L coordinates(L is the Mcllwain magnetic shell number). The location of the duskside bulge of the plasmapause has been shown to be inversely related to the solar wind speed. The total plasmasphere electron content (N_P) is supposed to increase with increase in L, the rate of increase being dependent on the density distribution assumed and the L values under consideration. Thus one expects an increase in N_P to be associated with a decrease in V_sw and vice versa. In this letter we give an experimental verification of this for two magnetic storms associated with large changes in V_sw, and for which N_P and Vsw data are available. The results will prove useful in interpreting the disturbed time behaviour of N_P.