Ionospheric and magnetospheric disturbances caused by impacts of asteroids and comets

Disturbances in the Earth's ionosphere and magnetosphere caused by impacts of small asteroids and comets (with the size from 30-60 m up to 1-2 km) are studied. The 2D hydrodynamic numerical simulations of a cosmic body passage through the atmosphere with allowance for deceleration, deformation and disruption due to aerodynamic loading and formation of the wake behind the body are performed. A plume (a mixture of the air and the products of "explosion" after the impact onto the land or into the ocean) is formed. Rising plume reaches high altitudes, operating as a MHD generator. A part of the plume moves at higher than escape velocity and may pierce the ionosphere and magnetosphere. The MHD numerical simulation of the motion of the plume and its interaction with the geomagnetic field are performed. Excitation of MHD waves is demonstrated with amplitudes of 10(2)-10(3) nT. These disturbances are capable of triggering precipitation of particles from Van Allen radiation belts, increase ionization at lower altitudes, produce intense electromagnetic noise. Lower velocity parts of the plume increase the air density at large distances from the impact point. For an example, a 400-m stony body, with the initial velocity of 17 km/s impacting the ocean for the moments of 200-600 s increase the density in the cylinder with radius of 1600-1800 km and altitude to ~2000 km up to the density of 10(-14) g/cm3, which corresponds to the normal density at an altitude of ~350 km. That changes the recombination rates and increases the ionization due to the solar radiation and cosmic rays. This effect resembles rising the F2 layer of the ionosphere up to altitudes of 1000-2000 km. Radii of the density disturbances at higher altitudes are much larger - they reach 5000-7000 km at an altitude of 1200 km at the same moments of time. Low-velocity part of the plume falls back due to gravity and produced intense oscillations of the ionospheric conducting layers propagating to very large distances from the impact point. The disturbances may have global character.