Physics of auroral phenomena : proceedings of the 39th annual seminar, Apatity, 29 February-4 March, 2016 / [ed. board: N. V. Semenova, A. G. Yahnin]. - Апатиты : Издательство Кольского научного центра РАН, 2016. - 167 с. : ил., табл.

SC-associated VLF-emissions at two closely spaced auroral stations We suppose that there were stored a lot of resonant trapped electrons due to previous geomagnetic activity with Kp=5 in the Earth radiation belt. It is the necessary condition for the development of the electron cyclotron instabil­ ity caused by the SC impulse. That was shown by Kleimenova and Osepian [1982] who studied the SC effects in VLF emissions at subauroral latitudes. It was found that the SC associated VLF bursts occurred only if previous geomagnetic disturbances Kp >2. The VLF gap (-11.20-11.30 UT) between the VLFsc burst and the following VLF hiss onset corresponds to the strong pressure depletion observed by ThD satellite (Fig. 7) and energetic particle decreasing (both, electrons and ions) measured by ThE and ThD satellites. The ground-based VLF data showed [e.g., Klemenova et al., 1968, Smirnova et al., 1976] that the strongest day­ time hiss was observed near the location of the plasmapause. Thus, the plasmapause can be a main wave channel guiding the plasmaspheric hiss from the magnetosphere into the ionosphere [/нал and Bell, 1977]. Then the VLF waves propagate through the ionosphere and due to travelling in the Earlh-ionosphere wave-guide, the waves could arrive at ground receiver, located far away from the wave exit point. The sense of the polarization vector rotation provides the information how far is the VLF wave receiver location from ionosphere exit point. We suppose that in the beginning of our event (the first minutes after SC), the VLF receiver at LOZ was located far away (strongly left-hand polarized waves at frequency of -2-4 kHz, Fig. 5) from the wave ionospheric exit point, which roughly coincides with the plasmapause projection to the ionosphere. So, the source of the VLFsc burst was very localized in longitude. However, the polarization of the succeeding long-lasting VLF hiss was right- handed both at LOZ and KAN supporting a broad ionospheric wave exit area. 4. Conclusion 1. The SC led to the excitation of a short VLF burst with the strong left-hand polarization at LOZ and both (left- and right- hand) polarization at KAN. The 2-4 kHz waves arrived to KAN along the N-S meridian, but at LOZ they arrived from West. This may be due to the location of KAN, which was closer to the ionospheric wave exit point than LOZ and support the small longitudinal dimension of the wave exit area. 2. We suppose that the 2-4 kHz VLF burst was induced by the solar wind dynamic pressure impulse, which gener­ ated the electron cyclotron instability in the Earth radiation belt near the plasmapause. Required number of trapped resonant energetic electrons was provided by previous geomagnetic activity (Kp=5) 3. 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