Ionospheric variability during quiet and disturb geomagnetic conditions for low and high solar activity year

Present Paper describes analysis of GPS-data recorded at low latitude station Hyderabad (Geographic latitude 17∘, 25′ N, longitude 78∘, 33′ E), India to study the effect of magnetic activity on ionospheric TEC. The total electron content (TEC) data were considered for the ionosphere during five most quiet and most disturbed days for each month of the solar minimum year 2009 and the high solar activity year 2013. The results show that GPS-TEC is found to be more during disturbed days than that during quiet days with a maximum difference during the equinox season. In addition, the difference in TEC during quiet and disturbed days is found to be higher for solar maximum than that for solar minimum year. Moreover the GPS-TEC variations depend on the season with the maximum in equinox season and minimum in summer and winter season. Generally daytime TEC is found to be larger than that in the nighttime which is maximized around the local noontime hour but the peak formation delayed for the solar minimum year. The EIA development process during the solar minimum is quite slow and occurs in late afternoon as compared to that during the high solar activity year. In addition, this delay is larger for summer and winter season than that for equinox months. The formation of post sunset anomaly in the post-sunset sector (1900-2300 LT) is prominent during high solar activity year 2013 whereas same is insignificant for solar minimum year 2009. The post-sunset anomaly could be attributed to pre-reversal enhancement (PRE) of zonal electric field. (author)