Conditional Climatology of Ap: The Relationship between Solar Flares and Geomagnetic Storms
AIR FORCE ENVIRONMENTAL TECHNICAL APPLICATIONS CENTER SCOTT AFB IL
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This report documents a study of USAFETACs optical solar flare database and its relationship to Gottingens planetary geomagnetic index Ap. The study was based on solar flare data with an 11-year period of record 1975 to 1986--Solar Cycle 21. After solar flares and Ap indices were studied separately, more than 27,000 flare reports were merged with 3-hour Ap values for 7 days after each flare. The resultant dataset was analyzed with respect to certain flare characteristics such as importance, brightness, duration, solar location, and phase of the solar cycle to find the best predictor of geomagnetic storming. The results were summarized in contingency tables provided in Appendix B for use as solar forecasting aids. Some flares were found to have more of an influence on the Earths geomagnetic field than others. Of all the features studied, a flares importance and location on the disk seemed to be best predictors of geomagnetic storming. Keywords Climatology, Solar flares, Solar disturbances, Sunsports, Solar activity, Solar atmosphere, Solar forecasting, Geomagnetic storm.