IONOSPHERIC AND ATMOSPHERIC DISTURBANCES AROUND JAPAN CAUSED BY THE ERUPTION OF MOUNT-PINATUBO ON 15 JUNE 1991

The disturbances observed by the Japanese ionospheric observation netw ork following the explosions of Mount Pinatubo on 15 June 1991, are pr esented. Remarkable ionospheric fluctuations with periods of about 20 min appeared in the records of HF Doppler and total electron content ( TEC) data. Traveling wave fronts of ionospheric disturbances scaled fr om these data give a northward horizontal velocity of 290 m/s. The sur face pressure fluctuations due to the passage of atmospheric waves wer e confirmed by the microbarograph chain data in Japan. There existed t hree kinds of northward traveling pressure fluctuations: short-period (2-5 min) fluctuations with a horizontal velocity of 290 m/s, long-per iod (8-10 min) fluctuations with 300 m/s, and 17-min fluctuations with 281 m/s. It is concluded that the ionospheric and surface pressure wa ves were caused by the eruption of Mount Pinatubo.