Estimates of meteoroid kinetic energies from observations of infrasonic airwaves

Signal properties of the acoustic waves produced from meteoroids impacting the Earth's atmosphere in the approximate size range of 0.1–10 m diameter have been analyzed at infrasonic frequencies. From these data, we have produced a series of empirical relations between the far-field acoustic signature of the bolide shocks and meteor source energies by correlating infrasonic observations of those fireballs which are also detected by earth-observing satellites. Adopting a similar approach as has been previously employed for man-made explosives, signal properties such as acoustic amplitude, signal energy/power and signal-to-noise ratio, are shown, after high-altitude wind corrections, to be useful tools in estimating the kinetic energy of a bolide. Comparison of bolide infrasound data to ground-based explosive tests show that the acoustic amplitudes from airwaves generated by small bolide events (7 kt) mimic man-made explosions in terms of range dependence, but offset in amplitude equivalent to ∼20 km source altitudes. This is consistent with instrumental observations of fireballs and the expectation that larger meteoroids (greater than a few meters in diameter), should penetrate deeper into the atmosphere on average. Applying these new relationships to historical events, we find that the August 3, 1963 bolide detected infrasonically near the Prince Edward Islands off the coast of South Africa, previously estimated to have an energy of 1100 kt, may have had a much smaller energy of 266±90 kt. This energy revision brings the infrasonically determined Near Earth Object (NEO) influx rate into much better agreement with that determined more recently using satellite and telescopic survey data.