Ionospheric effects of solar flares. IV. Electron density profiles deduced from measurements of SCNA's and VLF phase and amplitude

Abstract

A method is presented by which electron density profiles in the D-region of the ionosphere may be derived during solar flares from: 1. (1) SCNA measurements at two frequencies; 2. (2) simultaneous measurements of SCNA's and SPA's at VLF. A parabolic profile is assumed. At lower levels, the profile is estimated from the measurements of phase and amplitude changes at VLF. Profiles are obtained for a number of flare events, and are compared with those derived recently by cross-modulation, partial reflection and rocket techniques. It is observed that the enhanced electron density at 60 km is of the order of 100 cm^-3 during an average flare effect, about 900 cm^-3 around 70 km, but increases steeply with height to about 10⁴ cm^-3 around 85 km.