Strong Acoustic Gravity Waves from Impacts of Large Cosmic Objects

摘要

Numerical methods are employed to study the internal waves induced by a thermal-energy release of 1.25 x 10~(22) to 5 x 10~(22) J in the lower atmosphere in a region with a characteristic radius of about 1000 km.According to estimations,such a warming of the atmosphere can occur when shattered and molten rocks are ejected from the crater formed during the impact of an asteroid with a diameter of 15 km and a velocity of 15 km/s on the Earth.It seems likely that such an asteroid created the Chicxulub crater.According to the well-known hypothesis,this crater is associated with the global catastrophe that occurred at the Cretaceous/Tertiary boundary.Numerical solutions of the gas-dynamics equations are obtained using a second-order accurate scheme in spherical coordinates.During the propagation of a packet of internal waves in the lower atmosphere,maximum velocities of air near the Earth's surface are greater than 25 m/s everywhere,and greater than 30 m/s in the hemisphere where the energy release has occurred.This could lead to a general breaking of branches and to a partial felling of trees.The resulting large amount of dry wood appeared to serve as a cause of the spread of global fires.