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The seasonal effects in the thermosphere and\udionosphere responses to the precipitating electron flux and field-aligned\udcurrent variations, of the order of an hour in duration, in the summer and\udwinter cusp regions have been investigated using the global numerical model of\udthe Earth's upper atmosphere. Two variants of the calculations have been\udperformed both for the IMF By < 0. In the first variant,\udthe model input data for the summer and winter precipitating fluxes and\udfield-aligned currents have been taken as geomagnetically symmetric and equal to\udthose used earlier in the calculations for the equinoctial conditions. It has\udbeen found that both ionospheric and thermospheric disturbances are more\udintensive in the winter cusp region due to the lower conductivity of the winter\udpolar cap ionosphere and correspondingly larger electric field variations\udleading to the larger Joule heating effects in the ion and neutral gas\udtemperature, ion drag effects in the thermospheric winds and ion drift effects\udin the F2-region electron concentration. In the second variant, the calculations\udhave been performed for the events of 28–29 January, 1992 when precipitations\udwere weaker but the magnetospheric convection was stronger than in the first\udvariant. Geomagnetically asymmetric input data for the summer and winter\udprecipitating fluxes and field-aligned currents have been taken from the\udpatterns derived by combining data obtained from the satellite, radar and ground\udmagnetometer observations for these events. Calculated patterns of the\udionospheric convection and thermospheric circulation have been compared with\udobservations and it has been established that calculated patterns of the\udionospheric convection for both winter and summer hemispheres are in a good\udagreement with the observations. Calculated patterns of the thermospheric\udcirculation are in a good agreement with the average circulation for the\udSouthern (summer) Hemisphere obtained from DE-2 data for IMF By\ud\ud< 0 but for the Northern (winter) Hemisphere there is a disagreement at high\udlatitudes in the afternoon sector of the cusp region. At the same time, the\udmodel results for this sector agree with other DE-2 data and with the\udground-based FPI data. All ionospheric and thermospheric disturbances in the\udsecond variant of the calculations are more intensive in the winter cusp region\udin comparison with the summer one and this seasonal difference is larger than in\udthe first variant of the calculations, especially in the electron density and\udall temperature variations. The means that the seasonal effects in the cusp\udregion are stronger in the thermospheric and ionospheric responses to the FAC\udvariations than to the precipitation disturbances. Key words. Ionosphere (ionosphere · atmosphere\udinteractions; ionosphere · magnetosphere interactions; ionospheric\uddisturbances)

Seasonal effects in the ionosphere-thermosphere response to the precipitation and field-aligned current variations in the cusp region