Statistical properties of variability of the quiet ionosphere F2-layer maximum parameters over Irkutsk under low solar activity

The statistical analysis of the quiet ionosphere F2-layer maximum parameters variability (deviations of NmF2 and hmF2 from the quiet medians, delta n and Delta h) under solar minimum at day (10-16 LT) and night (22-04 LT) hours based on data of Irkutsk station for 2007-2010 is presented. It is found that the experimental distribution (histogram) of delta n can be approximated by a mixture of two normal distributions. The first and second components of the mixture characterize, mainly, relatively weak and strong fluctuations of delta n which are presumably associated with the ionospheric effects of the atmospheric gravity waves and of the planetary waves and tides correspondingly. Deviation of the delta n histogram from a single normal distribution is most considerable at night hours in winter and equinoxes. For these conditions the weak fluctuations of delta n are mainly negative and the strong ones are mainly positive. The Delta h histogram is a normal distribution except day hours in winter and equinoxes when a weak deviation of the histogram from the normal distribution occurs. (C) 2012 COSPAR. Published by Elsevier Ltd. All rights reserved.