Response of the ionosphere to the Alma-Ata earthquake on 4 March 1991

Experimental data on the response of the ionosphere to the Alma-Ata earthquake of 4 March 1991 are presented. It is shown that the ionosphere reacted to a sound wave that rose to a height of 200 km in 540 sec. Two successive responses to the earthquake were observed directly above the epicenter, one of which was evoked by the propagation of the sound wave. The 'fast' response of the ionosphere was determined by the sound-wave propagation up to 100 km and the penetration to greater heights of an electric field generated by the sound wave in the dynamo region.