The application of solar and geomagnetic data to short‐term forecasts of ionospheric conditions

Abstract

The program for the systematic collection of current solar and geomagnetic data coordinated at the Department of Terrestrial Magnetism of the Carnegie Institution of Washington (DTM CIW), particularly for application to short‐term forecasting of magnetic and ionospheric disturbances, has been in progress since July, 1942. The ways in which recurrence‐tendencies of geomagnetic activity, reports of solar activity, and various solar‐terrestrial relationships are used in preparing the forecasts are described in this report. The forecasts issued by the Interservice Radio Propagation Laboratory (IRPL) in collaboration with DTM CIW are compared with magnetic activity for a 15‐month period and show that the forecasts are satisfactory about 70 per cent of the time. The correlation‐analyses of coronagraphic and spectroheliographic data with magnetic activity show that over a period of two years there was a decided tendency for disturbances to occur when solar regions identified by these observations were east of the central meridian of the Sun. Reductions of solar and geomagnetic data indicate that a minimum in solar activity occurred early in 1944, but that the minimum epoch of geomagnetic activity cannot as yet be defined. Reference is made to the application of visually recording magnetographs developed at DTM CIW.