Total electron content observations at Calcutta with geostationary satellite INTELSAT 2F2

Observations from a geostationary satellite over the Indian subcontinent have been carried out at Haringhata Field Station of the University of Calcutta (geogr. lat., 22 deg 58 min N, long., 88 deg 30 min E; magnetic dip, 32 deg N) with the help of INTELSAT 2F2 transmitting at 136.44 MHz. The Faraday fading data obtained during winter 1972-73 have been analyzed to determine electron content, slab thickness and effect of magnetic activity on nighttime content at a location with subionospheric latitude of 20 deg N and longitude 90 deg E. The diurnal curves of electron content during the winter months indicate a range of about 1:12. A considerable day-to-day variability in the midday values as well as a variability in the time of onset for the afternoon decay is observed. The rate of increase in electron content after sunrise is substantially constant at 10 to the fifteenth power el. per sq m per min upto about 0930 hrs IST and shows an abrupt increase thereafter by nearly a factor of 3 when ionization from the equatorial region diffuses into the local ionosphere. The period under study was marked by several weak-to-moderate magnetic storms, which induced high values of midnight content as large as 100% above the mean value.