Global modeling of the quiet and disturbed upper atmosphere

Abstract

The behaviour of the sub-auroral and auroral ionosphere over Scandinavia in November 1995 has been numerically simulated. The results of the simulation have been compared with the data mapping the ionospheric F-region by means of satellite tomography and of the empirical reference ionospheric model. A good similarity has been achieved comparing the theoretical model calculation and the ionospheric tomography and empirical model data, after correcting the total intensity of the solar EUV flux.To test various hypotheses about positive ionospheric storm development, a numerical simulation case study for the magnetic storm of 24–27 January 1974 has been performed to obtain the global pattern of the thermospheric and ionospheric effects of this magnetic storm. During the storm maximum the ratio [O]/[N2] is decreased by more than a factor 10 in comparison with the quiet time level at high latitudes, whereas at low latitudes this ratio is not changed, though the absolute density of all neutral constituents is enhanced. Meanwhile, the ionospheric storm is positive at low latitudes. We conclude that the positive phase of ionospheric storm is mainly due to upwelling of ionospheric F2-region plasma at mid-latitudes and that moving of this plasma equatorwards at low latitudes is caused by the disturbed thermospheric winds.