Solar-terrestrial relations and short-term ionospheric forecasting

Since the ionosphere is produced by the quiet Sun and disturbed by the active Sun, short-term ionospheric forecasting is discussed in three stages: (1) forecasting the solar activity; (2) the relations between the solar activity and geophysical disturbances, particularly magnetic storms, daylight fadeouts and polar cap absorption; (3) the effects of these geophysical disturbances on the ionosphere and on ionospheric radio communications. A short history of the subject is given, the international arrangements for collecting and rapidly exchanging the required solar and geophysical data are outlined, and short-term forecasting services at present operating are described briefly.