Ionospheric effects of solar flares. VI. Changes in D-region ion chemistry during solar flares

Abstract

Evidence has been presented by Rows et al. (1970) and in some of the preceding papers of this series showing a drastic decrease of the effective recombination coefficient during solar flares. In this paper, the sixth in the series, we examine the nature and magnitude of the decrease as a function of flare flux, develop model recombination coefficient profiles for different flare conditions, and then offer a theory of how these decreases can occur. A new ion chemical scheme consisting of a six-ion (four positive and two negative) model is presented. It is shown that this decrease is due to different relative increases in the electron density and the negative ion density, or to a change in the dominant positive ion from a complex hydrated ion with a large recombination coefficient to a simple ion with a smaller recombination coefficient. At 70 km the former effect seems to be operating, while at 80 km the latter effect operates.