meteoroid kinetic energy, acoustic efficiency, mean wind speed, acoustic signal duration and time delay, moving shock parameters, oscillation period, Astronomy, QB1-991

Purpose: The parameters (period, time delay, celerity, duration, and the rate of attenuation) of the acoustic signal which was generated during the Chelyabinsk meteoroid passage and explosion on February 15, 2013 are investigated along with atmospheric parameters. Design/methodology/approach: With the temporal variations in the level of the acoustic signals acquired at an array of acoustic stations, the principal signal parameters are determined and their comparison made with the model results. Findings: The time delay of the infrasound signal has been shown to increase approximately linearly with the distance between the acoustic source and an observation station. The mean celerity of the infrasound wave is approximately 270 m/s. The signal spectrum exhibits components with periods of 10÷100 s, and the harmonic with an approximately 30-s period prevails. The duration of the infrasound signal is established by its source length (50÷90 km) and the infrasound signal spreading due to dispersion in the atmosphere that depends on the distance the wave has traveled. The overall duration of the signal is equal to 6÷30 min for the range of 540÷ 5780 km. The regression relations between the time delays and the acoustic signal spreading have been determined as a function of path length. The characteristic scale length of infrasound attenuation depends on a specific path and varies within 1000÷3000 km. The effect of the moving shock created by the explosion is shown to be much greater than the effect of the ballistic wave almost at all altitudes. Conclusions: The estimates substantially agree with the observations.