ON STATISTICAL CHARACTERISTICS OF ELECTRIC FIELDS OF THE THUNDERSTORM CLOUDS IN THE ATMOSPHERE

摘要

A series of features of the spectral characteristics of thunderstorm-cloud field perturbations is specified on the basis of long-term ground-based measurements of the electric field at remote locations. A significant increase in the spectral density of the electric-field variations during the thunderstorm has been observed. Maximum increase due to the pulsed field component, which is related to the lightning discharges, is observed in the fluctuation-period range from tens of seconds to several minutes. A significant increase is also observed in the range 0.5–1.5 mHz (10–30-min periods) in which the spectral density is increased by more than a factor of 10~4, whereas the increase factor at the lower frequencies is equal to 100 (about 10 times for the field). Quasimonochromatic components (with 10–20-min periods) in the frequency fluctuation spectra of an electric field of the powerful thunderstorm clouds, which drift by frequency at the cloud initiation, maturity, and dissipation stages are found. It is shown that presentation of the sequence of the pulsed field perturbations related to the discharges in the form of a pulse flow with independent intervals (Poisson flow) agrees with the form of the fluctuation spectrum of the observed field and leads to an estimate of 10 s for the average relaxation (regeneration) time of the field in the thunderstorm-cloud vicinity after the discharge.