Amplitude scintillation of 244 MHz and dynamics of ionospheric irregularity patches near the crest of the equatorial anomaly in the Indian sector

The results of observations on amplitude scintillations of a 244 MHz signal transmitted by the geostationary satellite FSC-2 obained at Calcutta (400 km subionospheric point: 21.1 deg N, 87.1 deg E), a location near the northern crest of the equatorial anomaly, during the declining but sufficiently high solar activity period of August '81-December '82 are presented. The seasonal variation of UHF amplitude scintillation shows prominent peaks i the equinoxes, considerable occurrence in the December solstice and a trough with practically no occurrence in the June solstice. The present UHF amplitude scintillation observations are compared with the 136 MHz amplitude scintillation observations obtained during the same period. Simultaneous amplitude scintillation observations over two beacon paths from the satellites FSC-2 and ETS-2 (400 km subionospheric point: 21 deg N, 92.7 deg E) at frequencies 244 MHz and 136 MHz, respectively, are utilized to obtain some information on the irregularity patch dynamics at the present location. Some statistics concerning occurrences of post-sunset irregularity paths over two ray paths in relation to subionospheric sunsets are presented.