“…For example, Kalinin et al (2010), Veli chko (2010), and Deminov et al (2011aDeminov et al ( , 2011b understand modeling of the distribution analytical form for the F 2 layer critical frequencies as the selec tion of any functional dependence that satisfactorily describes the experimental distribution of parameters affecting foF2 in the specified time interval and varia tion range. The Gaussian distribution ( ) Venttsel, 1969) is mostly selected as an initial foF2 dis tribution approximation:…”