Ionospheric Electron Concentration Enhancement during a Solar Flare

DURING solar flares, sudden increases of extreme ultraviolet (EUV) and X-ray flux produce abrupt increases of electron concentration ( N e ) in the sunlit part of the ionosphere. Because of their relatively short duration and the accompanying blackout in h.f. propagation, these enhancements of N e have hitherto been difficult to investigate, especially in the E region. We report here some results of applying a new technique, incoherent scatter radar, to this problem. The observations were made at Malvern (52.1° N, 2.3° W) during a solar flare on February 20, 1970.