Satellite Observations and Modeling of the Polar Ionosphere Under Conditions of the Dominant Azimuthal () IMF Component

The processes that occur in the polar cap region and depending on the IMF sign are considered. The paper describes the results of a comparative analysis of the distribution of field-aligned currents, auroral precipitation, ionospheric plasma convection, and electron density under conditions of northward IMF and the IMF component of opposite signs. The field-aligned currents and precipitating particles are obtained from the AMPERE and DMSP satellite data. The convection patterns are obtained from the SuperDARN and numerical models; the electron density is calculated using the empirical IRI and regional numerical models. It is shown that the disturbances in the northern hemisphere are concentrated near the pole and differ significantly at opposite signs. At +, the precipitation intensity at the center of the polar cap is much higher than at -. Moreover, only at By+ does the evening convective cell prevail over the morning one, providing a circumpolar flow of ionospheric plasma in a broader range of latitudes. The model electron density distribution in the polar cap shows the formation of a polar peak at + and a depletion at -, which corresponds to the direction of field-aligned currents and the structure of precipitation. If +, a ‘cyclone’-type structure is formed in the northern polar ionosphere, where the energy and momentum of the solar wind are effectively transferred to the ionosphere during several hours of the northward IMF.