The possibility of deducing ionospheric and field-aligned currents from ground magnetic perturbations

The possibility of separating the effects of ionospheric currents from those of field-aligned currents in high-latitude magnetic perturbation records obtained at the earth\u27s surface is discussed. We note that the ionospheric current consists of two basic elements : toroidal and poloidal components, where the divergence of the toroidal part and the curl of the poloidal part are both zero. Thus, if one can derive from the ground magnetic records the equivalent ionospheric current function which is directly related to the toroidal part of the ionospheric current flowing in a thin spherical shell, the curl of the ionospheric current that is given by the conductivity and electric field, is expressed by the scalar current function. It is shown that the combination of the ground magnetic data from a world network and a simple model of the ionospheric conductivity makes it possible to estimate both the ionospheric fields and currents. By taking the divergence, the field-aligned currents are also calculated