Short Term Ionospheric Variability in the Northern Hemisphere for Two Consecutive Solar Cycles

Abstract

Hourly values of the total electron content (TEC-Faraday content) collected at five stations in the northern hemisphere extending from the low to high latitudes lying in the narrow longitude zone of (270 ± 20) °E during the solar maximum years 1981 and 1989 respectively of the last 21 and 22nd solar cycles and also during the common solar minimum year 1985 are used to study the latitudinal variations of the day to day TEC variability. The effect of solar phase change in the variability is found to be the least for the midlatitude station of Boulder and most during the nighttime for the high latitude station of Goose bay. The magnetic disturbance generally enhances the TEC variability for the five stations during the three seasons of both solar phases and this effect seems to be somewhat higher for the mid and high latitudes during the equinox season of the solar maximum years. A spectral investigation of the TEC variability reveals narrowing of the spectrum from low to high latitudes during the solar minimum phase while the reverse seems to be the case during the solar maximum. While the low latitude TEC variability spectrum is not correlated to either the variability spectrum of S10.7 solar flux or to the mean equatorial Dst variations, the mid latitude TEC variations show a good positive correlation with the variability of Ap and the higher latitude TEC variations are negatively correlated with the variability spectrum of the daily mean Auroral electrojet (AE) indices.