Mapping of the polar electrojet current down to ionospheric D region altitudes

The High-Power Auroral Stimulation (HIPAS) heating facility has been used to modulate D region ionospheric currents at high latitudes, producing extremely low frequency (ELF) radio wave emissions. The behavior of these ionospheric currents can be deduced from a comprehensive study of the ELF signals received at a local field site. This paper examines the mapping of the polar electrojet current from the E region down through the D region, where it can then be modulated by the heater beam. Results have been obtained using a simple Cowling model of the electrojet. These results indicate that for an electrojet flowing at an altitude of 110 km with a scale size in excess of 100 km, the mapping of the horizontal components of the current can be completely characterized in terms of the Pedersen and Hall conductivities. This is attributed to the fact that the mapping becomes independent of scale sizes which exceed 100 km. Several ionospheric heating experiments are proposed, including beam steering for localized ELF generation in the mapped region below electrojets. 27 refs