Physics of auroral phenomena : proceedings of the 40th annual seminar, Apatity, 13-17 March, 2017 / [ed. board: N. V. Semenova, A. G. Yahnin]. - Апатиты : Издательство Кольского научного центра РАН, 2017. - 143 с. : ил., табл.

J. Manninen et al. KAN & 24 Dec 2011 19-20 UT m M ■,i4 *8 ч* W Ur Figure 6. The change of QP dynamic spectral structure during the development of polar substorm (upper panel), the middle panel - the arriving wave direction, the bottom one - the substorm at HOR station. 24 Dec 2011 b Figure 7. The vectors o f the magnetic field (a) and Pi3 pulsations (b) at the substorm onset. A possible influence o f the considered polar substorm on the VLF wave propagation was observed as amplitude changes of the navigation (f~20-25 kHz) transmitter signals (Fig. 8b) that crossed the polar cap and which were monitored at KAN. In Fig. 8a the shadow represents the night-side region o f the Earth at 19:30 ITT. The transmitter locations and the VLF the propagation paths between the transmitters and the receiver are shown in Fig. 8a. The scheme of a polar substorm influence on the VLF propagation path is presented in Fig. 8c. Discussion We suppose that the frequency o f 2.5 kHz, which separated the “candles” and “front foots”, roughly coincided with one half o f the equatorial electron gyrofrequency (fee) value at L-value of the most plausible location of the plasmapause under Kp ~ 1 (L ~ 5.1 - 5.2). Then, we could expect that the high frequency (2.5-5.5 kHz) VLF “candles” are generated inside the plasmasphere, and the low frequency (1.7-2.5 kHz) “front foots” - outside. The lowest part 52