Mary W. Sowers and Margo PoKempner

Abstract: Data from 21 ionospheric sounding stations in the northern and southern hemispheres were used to characterize the day to day variation in the critical frequency of the F2 layer of the ionosphere. Variability in the critical frequencies are analyzed monthly and diurnally for quiet magnetic conditions during both low and high solar periods. In addition, variations in the F2 layer critical frequency are presented for active magnetic conditions during equinox periods. Tables of variabilities for each ten degree increment in magnetic latitude are also provided in this report. The dependence of variations in the critical frequency with the solar cycle index IG12 is also discussed.

Keywords: variability; critical frequency; F2 layer; magnetic latitude

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