Meteor-generated infrasound.

An analysis of the generation and propagation characteristics of infrasonic pressure waves excited during meteor entry into the earth's atmosphere is presented. Possible line source sound producing regions are determined for an assumed range of meteor entry parameters, gross fragmentation phenomena being neglected. A pressure wave model of a line source cylindrical blast wave produced by a high-velocity meteoroid in a continuum gas is then formulated by using similarity theory. It is found that the strong shock behavior of the blast wave is confined to a cylindrical region whose radius R0 is proportional to the product of the meteor's Mach number and its diameter. By using the numerical blast wave solutions of Plooster as initial conditions a description of the wave form far from the source is obtained. Both refraction and attenuation of the airwaves are then calculated separately in an approximate manner. For meteors with an associated R0 ≲ 10 m for source altitude regions determined earlier, predicted attenuation is very severe. Dominant wave periods predicted for arrivals at the ground are 0.4–2.5 s for sources with 10 ≤ R0 ≤ 100 m. Finally, infrasonic data from Goerke, from Shoemaker, and from Johnson and Wilson for four recent events are analyzed. Kinetic energy estimates which are obtained range from 1017 to 1022 ergs, each with an uncertainty of about 2 orders of magnitude.

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