Gasdynamical model of the Tunguska fall

The following are reliably established consequences of the Tunguska fall: a forest fall with an area of about 2000 km2 and the absence of a meteoric crater. Thus far, no substances have been found which are believed to belong to the Tunguska object. It is shown that the question about the source of the Tunguska explosion can be eliminated by modelling the events as a rapid evaporation of the meteor with subsequent movement, deformation and braking of a gas volume which consists of the products of evaporation in a mixture with air. Using parameters of the Tunguska space body from the work of Korobeinikov et al. (Astron. Bull. 25, 327–343, 1991) an ablation parameter of 25.5 is determined. Using the asymptotic form of the solution for trajectories at large ablation parameters, it is found that the evaporation of a snow-ice sphere occurs at an altitude between 20 and 37 km. The gas products continue moving, being mixed with air and rapidly decelerating. The last phase of the Tunguska phenomenon—the fall on Earth of a shock wave and the gas driven after it—explains the forest fall and burning of trees and the absence of an impact crater.