COSMIC NOISE AND IONOSPHERIC ABSORPTION OBSERVATIONS IN ANTARCTICA

Two 30 MHz riometers with Yagi-Uda antenna type, pointing one to the zenith and the other to the south at 400 zenith angle, were installed and operated from Dec. 27, 1987 to Mar. 8, 1988 and since Dec. 24, 1988 when a thirth riometer directed to the west was also installed at the Brazilian station Comandante Ferraz (520 S mag. latitude, L= 2.19) in Antarctica. The measured diurnal variation of the cosmic noise, during geomagnetically quiet periods, were compared to a theoretically obtained performing an integration on the sky within the antenna solid angle. The result are fairly coincident for the case of the vertical direction but somewhat different for the case of the southern direction. Some distinct absorption events of few hours duration typical of energetic electron precipitation and others due to solar X-ray bursts were observed.