Physics of auroral phenomena : proceedings of the 38th annual seminar, Apatity, 2-6 march, 2015 / [ed. board: A. G. Yahnin, N. V. Semenova]. - Апатиты : Издательство Кольского научного центра РАН, 2015. - 189 с. : ил., табл.

J. Manninen et al. The daytime peculiar discrete high-frequency VLF signals. These emissions were discovered only after an applying of the specific high frequency filtering of the impulsive signals like atmospherics. Fig. 4 shows the result of this filtration: left plot presents an ordinary 1-hour spectrogram without the filtration. The very strong atmospherics are seen. The right plot demonstrates the same spectrogram after the applying of the atmospheric filtration. One can see some peculiar discrete high frequency signals which were hidden earlier by atmospherics. Figure 4. 1-hour spectrograms in the frequency range of 1-16 kHz: the left plot - without filtering, the right one - after high frequency filtering.The strong horizontal lines - power line signals. Thus, the application of high frequency filtration allowed us to establish the new, previously unknown high- frequency VLF emissions. Some of them were observed in the daytime under quiet geomagnetic conditions. The investigations of these emissions are just in beginning. One typical event is presented in Fig. 5. We cut off the high frequency of spectrograms up to 11 kHz to avoid the 12 kHz (and higher) navigation transmitter signals. The analysis showed that the considered high-frequency signals were right-hand polarized (right panel in Fig.5), that supports that the ionosphere exit point of these signals is located in the vicinity of the receiver. The dynamic spectra of separated short bursts demonstrated the complicated noise-like rising structures in the frequency range of -6-9 kHz. The generation mechanisms of these waves are still unknown. в1-** - « j r r р я ж а т я * at?-»t 4 -иййЙ -if Figure 5. The left panels 1-hour (upper plot) and 5 min (bottom plot) spectrograms in the frequency range of 1-1 1 kHz: the left plot - the spectrogram without filtering, the right one - the same spectrogram after high-frequency filtering. The right panels show the right-hand (R) and left-hand (L) polarized signal power. Ъ М ф ь** Jtft» i* *5 v Э М ви? CM*** » 7m *y ШШЯнжеЛ 62