Physics of auroral phenomena : proceedings of the 37th Annual seminar, Apatity, 25 - 28 February, 2014 / [ed. board: A. G. Yahnin, N. V. Semenova]. - Апатиты : Изд-во Кольского научного центра РАН, 2014. - 125 с. : ил., табл.

consisted of several varying frequency bands as it was demonstrated at the left panel of Fig. 3. The central frequency of Pci waves and the spectral width significantly increased. Geomagnetic P ci pulsations in the solar activity minimum Figure 3. The spectral structure of Pci pulsations under magnetically disturbed period (left panel) and under very quiet condition (right panel). The geomagnetic latitude of stations is shown behind the station cod. Discussion According to [.Feygin and Yakimenko, 1971; Gendrin at al., 1971], the frequency band of a Pci wave packet could be determined by the expression: x ______, where n - the number of the equator wave crossing, a ,/2( a 2+ /?2) ' V n - ^ a | a =L L I are the terms of the expansion of the frequency ( CO ) and grow rate ( Y ) by the wave dk2 dk2 *” number ( к ); V n = 1. . . The growth rate ( у ) depends on the very important magnetospheric parameter * dk 0 ( V J U X where VA- the Alfven speed in the top of the magnetic field line, and is the average field-along speed of the anisotropic protons. The numeric calculations showed that under small values of the (VAI U ^ , the frequency Pci band could be small as well as the width of the wave spectra. However, under large values of this parameter, the frequency Pci band could become large. The result of this calculation is shown in Fig. 4 Figure 4. The wave spectral width dependence on the parameter (VA / ROV(63) 65