Physics of auroral phenomena : proceedings of the 34th Annual seminar, Apatity, 01 - 04 March, 2011 / [ed.: A. G. Yahnin, A. A. Mochalov]. - Апатиты : Издательство Кольского научного центра РАН, 2011. - 231 с. : ил.

Yu. V. Zubova et al. values up to 30 per cents. The UAM-T and UAM-MSIS-HWM versions produce the less evident WSA than in the UAM-MSIS results. foF2, MHz LT, hours LT, hours Fig-1. LT-latitudinal distributions of the foF2 values at the geodetic meridian of 285° calculated for December 23, 1985 by three UAM versions in comparison with the IRI-2001 data. The geomagnetic equator is marked by the horizontal solid black line. 23.12.1985 A=285° IRI-2001 O)a>•o a>■o UAM-TT UAM-MSIS-HWM O)ш T3 a>T33 го As it was shown in [Knyazeva and Namgaladze, 2008b] the main physical mechanism forming the middle- latitudinal enhanced electron density regions under quiet geomagnetic conditions is the ion drag induced by the thermospheric wind. In the night sector the equatorward neutral wind drives the F2-layer plasma to higher altitudes where the rate of ion losses in collisions with neutral molecules is lower. It results in electron density increasing. The vertical ion velocity induced by the meridional wind is proportionate to the coslsinl value, where I is the inclination of the magnetic field. When the geomagnetic and geodetic axes are not coincident, the coslsinl magnitude at the fixed geodetic latitude depends on the geodetic longitude value. Thus at the geodetic latitude of 45°N the cosl sinl value is maximal at the geodetic meridian of about 300° which crosses the Weddell Sea anomaly region. To check the leading role of the non-coincidence of the geodetic and geomagnetic axes we calculated the foF2 distribution by the UAM-T version with the coincided geodetic and geomagnetic axes. The results are shown in Fig.2 in comparison with the results of the UAM-T taking into account the non-coincidence of the axes. It is visible that the WSA disappears when the axes are coincided. foF2, MHz 23.12.1985 A=285° UAM-TT UAM-TT with the coincided geomagnetic and geodetic axes -g v f \^= = = = = = = 5 = = ^^^^rr'A A -30-< I, / / П n ' ' .....— __ Г о -60 ------ -— СГ—~ *60 - с 1 1 ' -... - л и й Я М » го Е W „ О ^ LT, hours LT, hours О Fig.2. LT-latitudinal distributions of the foF2 values at the geodetic meridian o f 285° calculated for December 23, 1985 by the UAM-T version with the non-coincident (left) and coincided (right) geomagnetic and geodetic axes! The geomagnetic equator is marked by the horizontal solid black line. 144