Investigation of the relation between solar activity indices and foF2

In this study, for the 21th solar cycle, the variation of the monthly-noon median values of foF2 on Slough and Rome is investigated by using different solar indices, such as solar brightness, Sun Spot Number and solar flux at 2800 MHz. In order to observe the seasonal relation between solar activity indices, all months in each solar cycle are orderedas equinox periods (March-April, September-October), summer periods (May-June, July- August) and winter periods (November-December, January-February). The importance and the variability of the relation are investigated by using basic regression analysis method. It is observed that there is a qualitative relation between the solar indices and the ionospheric foF2 and the relation changes with respect to the seasons. It is also observed that the relations between the solar indices and the foF2 in equinox and winter periods are stronger than those in summer periods. The size of the relation changes from an index to an index, a cycle to a cycle and a location to a location.