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W.N. Edwards (University of Western Ontario, Dept. of Earth Sciences), P.G. Brown (University of Western Ontario, Dept. of Physics and Astronomy), D.O. ReVelle (Los Alamos National Laboratory)
Investigation of a series of large and well-observed bolide events (> 0.05 kton) have allowed for the first time an empirical determination of the amplitude-energy relationship for bolide infrasound. Observed infrasonic signal properties such as maximum amplitude, estimated signal power and signal to noise ratio, as recorded by microbarometers over ranges of 250 to ~ 11,000 km, have been calibrated against optical yield estimates from previously published measurements by U.S. Department of Defense and Department of Energy Earth-observing satellites. Comparison between various bolide energies has required a scaled range to be defined that varies as R/W1/3 where R is the receiver range and W is the bolide energy or yield. This definition is derived from scaling laws discovered during investigations of free-air nuclear and high explosive tests during the 1950's and 60's. In addition, examination of stratospheric wind effects on the measured signal properties show that the observed scatter may be reduced and the relationships improved, though this may be considered a secondary effect when compared to other source characteristics. The new empirical bolide amplitude relationship is steeper and falls below similar curves for strictly point source, ground-level nuclear and high-explosive data. This downward shift has been interpreted to be due to increased weak non-linearity of the wave propagating from higher source altitudes. This is a likely explanation as a mean altitude of 20 - 30 km is found for the region of maximum source energy deposition, consistent with the terminal heights for fireballs of this size population.
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Bulletin of the American Astronomical Society, 36 #4
© 2004. The American Astronomical Soceity.