GNGTS 2024 - Atti del 42° Convegno Nazionale

Session 3.2 GNGTS 2024 Mefte lake. It appears as a well defned red-coloured band that develops irregularly in the central part of the recording between 50 and 200 Hz. It is a local oscillaton of the electric feld because it does not appear at both electrodes, and it was demonstrated to have a source not longer than some tenths of m large (Fidani and Martnelli, 2015). This is the phenomenon that we are searching to observe in connecton with the fuid escaping from the ground to study some kind of link between them. From the theoretcal approach (Fidani and Martnelli, 2015; Fidani et al., 2020), this signal should be generated by charged oscillatng clouds whose dimensions would be from tenths of cm to a few meters dimension. The charged cloud is a stable structure as the pressure force is supposed to balance the electric force. It was mathematcally demonstrated that such a physical system is able to oscillate, and the charge magnitude balancing slight pressure holes was estmated to depend on the oscillaton frequency. Charges from 10 -4 to 10 -5 Coulombs were associated with the measured frequencies. Being pressure variatons hypothesized for this kind of electrical sources, a comparison was made between the most intense electric oscillaton and acoustc recordings. searching for possible mechanical efects of oscillatng cloud transducton in pressure waves or thinking of fuid emission changes possibly related to electric oscillaton triggers. The comparison was made between respectve spectrograms. Being the acoustc signal initally sampled at 27 kHz, the spectral overlap with the electric ELF (up to 2 kHz) spectra was problematc, also due to the logarithm scale for ELF with respect to the linear for audio. The acoustc recording is reported in Figure 1 botom, for the same tme interval on December 12, 2022. No connectons appeared between intensites nor in shapes. Higher audio frequency recordings seem to be related to wind, whereas the corresponding frequencies of the electrical oscillaton were restricted in the violet band of Figure 1 botom. A reducton of audio sampled frequency was frst decided to reduce the wind infuence, and a plot in the logarithm scale was realized for a beter comparison with the electric recording. Fig. 1 – Spectrograms recorded on December 22, 2022, from 19:52 to 22:19 LT; the tme is marked every 5 minutes by the vertcal doted lines. Frequency was reported in the logarithm scale on the y-axis and power of signals in dB by a colour legend. Two bands are related to the electrode E-W on the top, and to the microphone recording below. Labels on the lef and in the middle referred to the power spectra intensites and tmes of the spectrograms.