THE INTENSE IONOSPHERIC ABSORPTIONS ASSOCIAfED WITH R9O77

Using the ground observation data at Zhongshan Station of Antarctica during July 13 to 17, 2000, the intense absorption events associated with the activities of the solar active region R9077 are analyzed. It was shown that an intense polar cap absorption event lasted more than 3 days, which was caused by the solar proton event accompanying the X5/3B major flare at 1024UT on 13 July The polar cap event started at about 1040 UT on July 14, and lased to bo 1940UT on July 17, with a typical day-night variation. At the same time, the intense solar activities extremely disturbed the magnetosphere, therefore aurora substorms occurred frequently. The energetic particle precipitation from the magnetotail caused several absorption spikes superimposing on the background of polar cap absorption. The distinct event is an absorption enhancement that started at about 0300 UT on 15th, reached its peak of 26dB around 0645 UT and recovered at about 1110 UT on the same day, which was the strongest absorption event observed at Zhongshan Station since the imaging riometer installed in February, 1997. Another outstanding absorption spike with pulsation occurred at around 1753 UT on 14th, its peak reached 6 dB.