Physics of auroral phenomena : proceedings of the 33rd Annual seminar, Apatity, 02 - 05 March, 2010 / [ed.: A.G. Yahnin, A. A. Mochalov]. - Апатиты : Издательство Кольского научного центра РАН, 2011. - 206 с. : ил.

M.A. Knyazeva at al. The most evident differences between all model calculations of foF2 diurnal variations take place for the night-time sector results. The main role in the night-time peak F2-layer behaviour plays the meridional wind. April N X CN LL e 10 8 6 4 2 400 E <N300 E -C 200 100 <л E 0 | -100 -200 5 CM z cf О 'с 1 day 2 day IRI-2001 -UAM-MSIS Q . F2 UAM-MSIS-HWM 3 day UAM-TT Figure 1. The calculated F2-layer critical frequency (foF2), height o f the F2-layer peak (hmF2), northward neutral wind velocity at the altitude of 300 km (K„) and ratio of the О and N2 concentrations at the altitude of 300 km (; n(0)/n(Nz)) diurnal variations over Slough ( top-down ) for April 16, 1988. The IRI-2001 data are pictured by solid line, the Q-F2 data - by solid line with black bubbles, the UAM-MSIS values - by dotted line, the UAM-MSIS-HWM values - by dotted line with circles, the UAM-TT values - by solid line with squares. The ionospheric plasma transfers along the geomagnetic field lines by the equatorward neutral wind to the higher altitudes thus decreasing the ion loss rate. As a result the hmF2 and f,F 2 increase. The meridional wind velocity calculated by all UAM versions is equatorward in summer solstice and spring equinox. The UAM-MSIS version gives larger values than the UAM-TT. It explains the differences between hmF2 and foF2 values calculated by these UAM versions. The UAM-TT version underestimates the day-time foF2 values at the end of the third twenty-four hours integration period in all seasons. The day-time n(0)/n(N:) values do not change practically in winter and summer conditions, but in spring equinox the ratio values decrease. The poleward wind velocity increases and that causes decreasing of the hmF2 and f„F2 in winter and summer solstices. In spring condition the Vnx values calculated by the UAM-TT version do not change. 1 2 2