Numerical modeling of Tunguska-like impacts

A two-dimensional numerical model with radiation and ablation is developed for the study of the impact of rather large (several meters or several tens of meters) meteoroids. This model is applied to consider the vertical impact of a 30 m in radius cometary projectile. Numerical simulations clearly demonstrate the two main stages in the meteoroid's evolution. During the first stage the falling body is deformed, flattened and finally transformed into a high velocity debris jet. At the second stage the elongated debris jet is decelerated, and the most of impact energy is released. After the full stop of the jet at an altitude of about 4 km the formation of rarefied entry column is completed. Hot air and vapor in the entry column accelerate upwards and form a ballistic plume. Deceleration of the plume by gravity, fall-back and deceleration of plume material near the 100 km level, lead to the formation of a disk-shaped area of compressed and heated gas. These perturbations, with a scale of about 1000 km , are believed to be responsible for the geomagnetic effect detected by Irkutsk observatory after the Tunguska event.