Ionospheric F0 F2 data and its response to solar activity cycles 21, 22, and 23

Some results may be noted as follows:

Отклик состояния ионосферы , характеризуемого foF2, на солнечную активность в 21, 22 и 23 циклах

• •    f 0 F2 shows double maximum during cycles 22 and 23 as solar activity indices show.

• •    The hysteresis between f 0 F2 and SF (10.7 cm) is much higher in the southern hemisphere than the northern one.

• •    An asymmetry exists between solar activity indices and f 0 F2 during the maximum of cycle 22.

• •    Solar activity indices generally show a decrease on the amplitude values during cycle 23, but f 0 F2 does not show this decrease.

• •    f 0 F2 follows the solar activity cycles, however A p index does not show the same shape. It reaches maximum values during the beginning and the end of the activity cycles.

B.U. Kandilli Observatory and Earthquake Research Institute Astronomy Laboratory, Istanbul, Turkey