Spatial inhomogeneity of variations in the F 2 layer critical frequencies under the conditions of winter 1995

Abstract

It is necessary to study properties of largescale ionospheric inhomogeneities in the F 2 layer in order to construct theoretical models of this phenomenon. An analysis of statistical properties of the sets of relative variations in the {δfoF2} critical frequency is one of the methods of such study. In this case it is of special importance to establish the measure of deviations from the standard distribution for the probability den� sity function of the δfoF2 value. Such deviations indi� cate that structural formations, corresponding to largescale inhomogeneities in this case, are present in the {δfoF2} set. The third and fourth statistical invari� ants (asymmetry A and excess E) are the measures of such deviations (Handbook, …, 1965). In reality, the sample volume is always finite. Therefore, studying the statistical properties of the sets of critical frequency relative variations {δfoF2} has a number of specific methodological features. The main feature consists in a deficit of information, owing to which a standard distribution is mostly used to model the ionospheric statistics. However, it is possible to overcome the limi� tations of the model of δfoF2 statistical variations in the form of a standard distribution, specifically, by using selective asymmetry A and excess E of a set, which are more complex nonlinear operators of the δfoF2 set scalarization and are the parameters of the new mathematical model of the probability density function. The aim of this work is to consider the spatial variability of asymmetry and excess of the relative vari� ations in the critical frequency of the ionospheric F2 layer at middle and high latitudes, using the set of data on the critical frequency variations in the highlatitude F 2 layer in January 1995.