Seasonal changes in daily variations of ELF-VLF atmospherics detected at auroral latitudes

Daily variations in the intensities of atmospherics at 600 Hz and 6 kHz detected at the Lovozero observatory from June to December 2012 were studied. Under quiet geomagnetic conditions, daily variations of atmospherics are shown to be determined by both the waveguide parameters of the Earth’s ionosphere and the activity of storm centers. In summer, a broad daytime maximum of atmospherics flow Nhr (the number of atmospherics per hour) is detected most likely due to the lightning activity in mid-latitude regions that are nearer to the observatory than the global storm centers. The daily variations in atmospherics mean amplitudes per hour Ahr differ appreciably from the daily variations Nhr, reflecting largely the changes in lighting conditions along signal propagation paths. The distribution function of the levels of atmospherics can be approximated by the following formula taken from publications: P(X) = [1 + (X/X50)k]−1, where k is a parameter that changes from 2.2 to 3.2 at f = 600 Hz and from 1.5 to 2 at f = 6 kHz under quiet geomagnetic conditions.