Abstract
Lightning flashes result in an instantaneous emission of electromagnetic
(EM) waves that encompass a broad spectrum of frequencies in the domain of radio
waves. The signature of these impulses in the region of the very low frequency (VLF)
of radio waves and bellow are called spherics. These impulsive signals traverse great
distances in the waveguide between the Earth’s ionosphere and its surface. Due to
the abundance of lightnings the lower end of the EM spectrum is dominated by the
waveforms of these emission. It is called atmospheric radio noise because of its origin.
This article outlines a straightforward approach for capturing spherics activity within
the VLF radio wave range. Employing data processing techniques, we pinpoint the
timestamps of spherics within time series data. The distribution of inter-spheric times is
analyzed across various detection threshold levels. Utilizing recordings spanning two
distinct years and seasons, we replicate the established form of the inter-spheric time
distribution described in the literature. Notably, we demonstrate that by rescaling the
time intervals between spherics with the mean time for a specific recording and given
detection threshold, the distributions collapse to a master curve. This universal pattern
is accurately characterized by a single-parameter mean-scaled Gamma distribution.
Additionally, we note the similarities in the distribution of inter-spheric times with
patterns found in earthquake recurrence times.