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 network following the explosions of Mount Pinatubo on 15 June 1991, are presented. 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 from these data give a northward horizontal velocity of 290 m/s. The surface pressure fluctuations due to the passage of atmospheric waves were confirmed by the microbarograph chain data in Japan. There existed three kinds of northward traveling pressure fluctuations: short-period (2-5 min) fluctuations with a horizontal velocity of 290 m/s, long-period (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 waves were caused by the eruption of Mount Pinatubo.