SOLAR-TERRESTRIAL DISTURBANCES OF JUNE-SEPTEMBER CORRESPONDING IV. IONOSPHERIC DISTURBANCES; 1. SOLAR X-RAY FLARES AND THEIR CORREPSONDING SUDDEN IONOSPHERIC DISTURBANCES.

As for the solar X-ray flare, some events which occurred in June, July, and September 1982 are comparable to the events which occurred in August 1972 but none of them exceed any event in August 1972. The maximum radiation flux 0. 1 approximately 0. 8nm) of the largest event on July 9 was 0. 98 multiplied by 10** minus **3 Wm** minus **2. Enhanced fluxes of giant solar X-ray flares and their corresponding sudden phase anomalies (S. P. A. s) of VLF radio waves on long-distance circuits received at Inubo conform to the theoretical relation between both quantities obtained in the past. Physical quantities on the maximum S. P. A. are estimated from the relation. For example, the maximum lowering of the reflecting altitude attained 13. 3 km at solar zenith angle of 62. 5 degree in the July 12 event. Height distributions of enhanced electron density due to photoionization and of a total one are obtained through the steady solution.