What solar and geomagnetic activities does F2-layer critical frequency median correspond to in midlatitudes?

A correlation was found between indices of solar and geomagnetic activities for monthly foF2 median and average values of these indices on the basis of an analysis of data on the F2-layer critical frequency foF2 from Slough and Chilton stations for 1954-2013. It was found that there is no systematic difference between the index of solar activity for a median foF and the 81-day or yearly average index of this activity. Cases in which a foF2 median corresponds to high geomagnetic activity are about 3-4 times rarer than observed cases of this high activity. Therefore, the geomagnetic activity that corresponds to a foF2 median is lower than the monthly average index of this activity on average, and this difference increases as the geomagnetic activity grows. The behaviors of relations between solar and geomagnetic activity indices for a foF2 median and the average values of these indices almost coincide for periods of relatively high (1954-1995) and low (1996-2003) solar and geomagnetic activity. [ABSTRACT FROM AUTHOR]