GNGTS 2019 - Atti del 38° Convegno Nazionale

GNGTS 2019 S essione 2.1 295 AIR IONS ASSOCIATED TO THE ELECTRIC OSCILLATIONS RECORDED BY CIEN C. Fidani Central Italy Electromagnetic Network, Fermo, Italy “A. Bina” Seismic Observatory, Perugia, Italy For more than 13 years, since the Central Italy Electromagnetic Network (CIEN) started to continuously monitor electric fields in the atmosphere, a certain number of electrical phenomena have been repeatedly recorded. Specifically, electric oscillations in the Extremely Low Frequency band with amplitudes of several μV/m were diffusely recorded, with major intensities during strong seismic and meteorological activities.Amodel of charged clouds agreed with the electric and magnetic observations satisfying the laws of electrodynamics. This theory and observational measurements contribute to sustain the discovery of a new electrodynamics phenomena that commonly occurs in the atmosphere (Fidani and Marcelli, 2017). After that a significant probability of occurrence of strong earthquakes was assessed by Cinti et al. (2004), three major seismic sequences have occurred throughout three different regions of Central Italy over the last decade, by confirming the forecast. CIEN started to work following such forecast and was active in occasion of the April 6 L’Aquila earthquake in 2009, the May 20 Modena earthquake in 2012 and the Amatrice – Norcia – Capitignano sequence which occurred August 24, October 30 in 2016 and January 18 in 2017, respectively. Oscillations in electric amplitudes were recorded by CIEN during all these three periods with amplitudes greater than those normally measured. Electric oscillation intensities started to increase weeks or months before the main shocks reached a maximum in correspondence of the main shocks, maintained this level for days or weeks, and then started to decrease returning to normal values in few weeks (Fidani, 2018). Measurements by CIEN suggested localised floating sources in the atmosphere of limited dimensions able to generate local horizontal electric fields. One of the charge distributions able to guarantee cloud stability has spherical symmetry with a positive charge confined in a central spherical volume. It is divided from a negative charge density surrounding it, where the pressure difference between the center and a point far outside of the charged cloud oppose the electric force (Tennakone, 2011). To verify such a physical hypotheses an air ion counter was designed for measuring the concentration air ions during electric oscillation recordings (Fidani, 2018). However, the air ion detector revealed to be very sensible to humidity and beyond 90% in humidity the ion counter had many problems to detect air ions and seldom failed to record long series of data. Thus, a series of ceramic resistor were introduced inside the detector, see Fig. 1, to heat the instrument. Positive air ion charge always overcame the negative air ion charge. However, when a CIEN station detect electric oscillations an inversion of air ion charge can be expected as there is a discrete probability that electrodes of the stations and station itself are immersed in the negative charge of the cloud. Being so, a confirmation of the presence of charged clouds is the measure of such charge concentration inversion. Charge concentrations inversions also occurs during Fig. 1 - The DLY-6A2 air ion counter modified to allow it to work at high humidity levels, the ion number must be corrected as the detector efficiency vary with temperature.