Radio Physics and Radio Astronomy (Mar 2018)
CHARACTERISTICS OF THE INFRASOUND SIGNAL GENERATED BY CHELYABINSK CELESTIAL BODY: GLOBAL STATISTICS
Abstract
Purpose: The investigation subject is the statistical characteristics of the infrasound signal generated during the passage and airburst of the Chelyabinsk celestial body on February 15, 2013. The parameters under study include the time delay, amplitude, duration, period, celerity and its dependence on the distance to the epicentre of the airburst from the observation site and on the back-azimuth angle of arrival. The study aims at constructing correlation diagrams for the signal celerity and the distance, the signal celerity and the sine of the back-azimuth angle of arrival, the signal duration and the distance, the signal amplitude and the distance, the period and the period for the periods determined by two techniques, and at fitting simple analytical relations to the diagrams obtained. Here, the distance refers to the distance between the infrasound source and the infrasound station where the infrasound is observed. Design/methodology/approach: The data retrieved from the US Department of Defence, the Comprehensive Nuclear-Test-Ban Treaty Organization’s International Monitoring System database are used to determine approximate relations for the basic characteristics of the infrasound signal generated by the passage and airburst of the Chelyabinsk celestial body on February 15, 2013. Findings: The correlation diagrams for the infrasound signal celerity and the distance between the source and an observation station have been shown to exhibit a significant scatter with a mean of (286.0 ± 21.5) m· s-1. The model fits of the infrasound signal celerity to the signal duration, to the back-azimuth angle of arrival, and to the distance between the source and an observation station, as well as the model fit of the signal amplitude to distance, are determined. The correlation diagrams for the main oscillation periods obtained by two different techniques are constructed. Conclusions: The infrasound signal time delay increases virtuallylinearly with the distance between the infrasound source and the station. The infrasound signal celerity averaged over all paths is equal to 291 m m·s-1. The celerity dependence on distance is fit with a constant due to a large data scatter. The celerity dependence on the sine of the back-azimuth angle of arrival, both calculated and estimated, is fit with a straight line that gives mean values of the celerity (287-288 m m·s-1) and tropospherestratosphere winds (12-14 m m· s-1) along all paths. The dependence of the infrasound signal duration on distance is fit with a straight line, and the signal duration near the source is found to be 10.7 min. The spectral components with a period within 17 to 85 s predominate in the infrasound signal spectrum, and the period mean values estimated by employing different techniques vary from 35 to 39 s.
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