Day-to-day variability of ionospheric electron content over Waltair

Abstract

Polarization rotation data (l36 MHz)recorded from the geostationary satellites ETS-Il and SIRIO at a low latitude station, Waltair (17.7°N,83.3°E)during high (1978-79)and low(1984-85)sunspot number years have been used to study the day-to-day variability of the ionospheric electron content (lEC). The ratio of the standard deviation of daily IEC values to the mean IEC values has been used as a measure of the variability. The daytime ratios are reasonably constant and independent of season during both the sunspot number years. The nighttime ratios are higher (20-80%) during high solar activitv period compared to those (15-30%) of low solar activity period. A correlative study is made on the day-to-day variability in IEC_maxwith possible causative factors, such as solar 10.7cm flux, electrojet strength (Δ <i>H</i>) and magnetic index (<i>A</i>_p) during the low solar activity period. The IEC at Waltair shows a linearly increasing trend with 10.7 cm flux during three different seasons and with the electrojet strength only in summer, while it does not seem to depend on the magnetic index. However, the percentage variations in the diurnal lEC, when considered separately for magnetically quiet and disturbed days during three different seasons of low solar activity period, show a clear ‘mirror-image’ behavior only during summer.