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.

Contribution o fthe MHD wave modes to the global Pc5 pulsations TRO. 31 O ctober 2003, 11,00-12.00 UT. 2.8 -3.2 mHz. 31 O ctober 2003, 11.00-12.00 UT. 2.B -3.2 mHz. Y -com ponent Ey-com ponent Fig. 3. Hodographs of the magnetic field at TRO station (left) and the electric field obtained from EISCAT radar data (right) in the interval 11.00-12.00 UT at31 October 2003. From Faraday's equation it follows that the electric and magnetic components (normal to the geomagnetic field) of an electromagnetic wave are to be in quadrature to each other. Upon the penetration through the laterally homogeneous ionosphere, the Alfven mode undergoes the additional я/2 rotation, whereas the magnetosonic mode practically is not influenced by the ionosphere. The cause o f this fact is that a field-aligned current, carried by Alfven wave, does not penetrate into the atmosphere and on the ground one can see the magnetic response due to the Hall current. The magnetosonic wave does not carry a field-aligned current and propagates through the atmospheric gap freely. Therefore, for an incident Alfven mode the main axes of the polarization ellipses of ground В and ionospheric E are to be parallel to each other. An admixture of the magnetosonic mode into an incident wave will result in the deviations between the orientations of В and E ellipses. However, such deviation can be also caused by the lateral inhomogeneity of the ionospheric condactances. 31 October 2003 31 October 2003 Щ Щ # м 1 GOES-12, he \ 05.00 05.30 06.00 00.30 07.00 07.30 08.00 10.00 11.00 12.00 13.00 14.00 15.00 10.00 Fig. 4. Geomagnetic field variations at GOES-IO geostationary spacecraft and conjugate station MEA (left-hand panel), and at GOES-12 geostationary spacecraft and conjugate station PBQ (right-hand panel). 71