GNGTS 2018 - 37° Convegno Nazionale

340 GNGTS 2018 S essione 2.1 these reasons the physical model of electrically charged clouds where electric forces are balanced by gas pressure forces, was taken into consideration (Tennakone, 2011). It can be associated with a well known mathematical problem for spherical symmetry which produces simple solutions describing stable oscillations of the cloud. One of the charge distributions, see Fig. 1, correspondent to the charged cloud stability can be calculated in ρ(r) = (2 ΔP ε o /r o 2 ) 0.5 (3 - r/r o ) exp(-r/r o ) , which indicates that a positive charge is confined in a spherical volume of radius 3r o , where ε o = 8.85 10 -12 F/m is the dielectric constant and ΔP is the pressure difference between the centre and a point far outside of the charged cloud. With ΔP/P = 0.5 the oscillation frequency of charged sphere can be linked to its radius f = 20.5/ r o and the charge inside the sphere to the frequency Q = 6.7/ f 2 , so that for oscillation frequency of 50 Hz a sphere of 2.46 m must be considered which contains 2.7 10 -3 C. With ΔP/P = 0.1 oscillation frequency of 50 Hz requires a sphere of 1.08 m which contains 2.3 10 -4 C and an oscillation frequency of 200 Hz requires a sphere of 27 cm which contains 1.4 10 -5 C. This model is attractive because it suggests that with high charge concentrations, corona discharges in the spaces between the separate charges can render the cloud luminous and this explains some recordings of earthquake lights such as the observed luminous spheres (Fidani, 2010). To understand how much near the charged clouds went to the CIEN stations an average induced potential on electrodes can be calculated where r , r o and L are defined in Fig. 1. For L = 10 m and r o as calculated above, the distance between the centre of the sphere and the tip of the electrode resulted of r = 11 – 14 m. Therefore, the charged clouds touched and surrounded electrodes only with the external negative density charge. The charged cloud model did not contradict any experimental measurement made by CIEN (Fidani and Marcelli, 2017). It could be linked to seismic activity by crustal fluid migration which transport charges escaping into the atmosphere, at different temperatures and pressures with respect to the atmospheric ones. Pressure and electric forces balanced between themselves in the atmosphere generating stable structures which must pass near the CIEN stations to be revealed. To further confirm this model other types of physical measurements are now necessary and will form the next CIEN stations. For example, an air ion detector could reveal increased ion numbers when electric oscillations are detected. Moreover, experimental proof is needed to demonstrate fluid electrification escaping from the ground. Finally, the influence of meteorological activity on charged cloud movements such as wind direction and velocity must be investigated. The model DLY-6A2 air ion counter, which was used up to now, is designed for measuring the concentration air ions of both positive and negative charge. The instrument specifications are: ion concentration range between 1 and 1.5 10 6 ions/cm 3 , accuracy ± 5%; resolution 1 ions/ Fig. 1 - The charge distribution of the spherical cloud model and the pressure curve along the section A-A, where P ∞ is the normal atmospheric pressure. An electrode of the CIEN station with length L is indicated in red and have the tip at a distance of r from the centre of the sphere.