Abstract
Abstract. A new method to reconstruct the instantaneous convection pattern in the Earth's polar ionosphere is suggested. Plasma convection in the polar cap ionosphere is described as a hydrodynamic incompressible flow. This description is valid in the region where the electric currents are field aligned (and hence, the Lorentz body force vanishes). The problem becomes two-dimensional, and may be described by means of stream function. The flow pattern may be found as a solution of the boundary value problem for stream function. Boundary conditions should be provided by measurements of the electric field or plasma velocity vectors along the satellite orbits. It is shown that the convection pattern may be reconstructed with a reasonable accuracy by means of this method, by using only the minimum number of satellite crossings of the polar cap. The method enables us to obtain a reasonable estimate of the convection pattern without knowledge of the ionospheric conductivity.Key words. Ionosphere (modelling and forecasting; plasma convection; polar ionosphere)
Highlights
The pattern of ionospheric convection at high latitudes can be considered as a snapshot of the whole magnetosphere since it results directly from the magnetosphere-ionosphere coupling and reects the electric ®eld, electric current and plasmaow throughout the magnetospheric volume
It is believed that the antiSunward convection in the polar cap corresponds to the Sunward convection in the magnetosphere, and that the Sunward convection at low latitude parts of the cells is a projection of the antiSunwardows in the magnetospheric boundary layer
We propose to describe the convection in the polar cap ionosphere as a hydrodynamic incompressibleow
Summary
The pattern of ionospheric convection at high latitudes can be considered as a snapshot of the whole magnetosphere since it results directly from the magnetosphere-ionosphere coupling and reects the electric ®eld, electric current and plasmaow throughout the magnetospheric volume. Burke et al, 1979; Potemra et al, 1984; Rei and Burch, 1985) or by strong distortion of the common two-cell pattern (Heppner and Maynard, 1987) In any case, it reects important changes in the outer magnetosphere resulting from interaction with the solar wind, since the polar ionosphere is electrically coupled with the magnetospheric regions of interest via magnetic ®eld lines. In order to plot a convection pattern in the polar cap, it is sucient to know the electric ®eld (or the plasma velocity) vector along trajectories which cross all (or almost all) the stream lines This geometry can be barely reached by only one satellite crossing, but, as will be shown, two crossings give quite satisfactory results
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