Solar eclipse-induced E-region plasma irregularities observed by the Gadanki radar

Abstract

We investigate the generation of low latitude E-region plasma density irregularities that were triggered during a solar eclipse on 11 August 1999. The observations were made using the Gadanki radar. The present study shows that a solar eclipse can provide night-like ionospheric conditions which allow the excitation of plasma instabilities and the generation of irregularities in the E-region at multiple height regions, as happens routinely during post-sunset hours. We surmise that the echo layers were associated with long-lived metallic ion layers that were made manifest when the more abundant ordinary molecular ions disappeared through recombination in the absence of photoionization. We propose that the layers turned unstable via the gradient-drift instability mechanism. This is the first time that a solar eclipse has been conclusively shown to generate E-region plasma irregularities.