Effect of solar flares on ionospheric TEC at Varanasi, near EIA crest, during solar minimum period

Abstract

A solar flare is a sudden release of energy usually near a complex group of sunspots. The interaction of solar flare radiations with constituents of ionosphere produces immediate increase in the electron density in the ionosphere. The present paper describes the effect of solar flare on ionospheric total electron contents (TEC) using global positioning system (GPS) data recorded at Varanasi, a station situated near equatorial ionization anomaly (EIA) crest region during solar minimum period. In this study, total four flares have been selected to study the effect of solar flares on ionosphere during the year 2008, which is a solar minimum period. The enhancements on ionospheric TEC have been observed during the period of solar flares. The maximum enhancement of TEC during solar flare compared to quiet mean TEC up to 24 TEC units have been observed. A significant enhancement in TEC is observed at regions around the EIA crest region during the flare in association with: (a) the flare related EUV flux enhancement and consequent increased production of ionization, and (b) changes in the equatorial electrodynamics. The magnitude of enhancement in ionospheric TEC appears to be dependent on the class of the solar flare.