Theory of Shock-Wave Ionization upon High-Velocity Impact of Micrometeorites

Abstract

The relevant processes in shock wave ionization of a solid Fe micrometeorite impinging on a W target are analyzed. The internal energy behind the shock wave in shown to depend on impact velocity w, target and meteorite density in a simple analytical form. For low impact velocities (w<7 km sec-1) the ions generated by the shock are mostly due to surface ionization. For high impact velocities [w>20 km sec-1) the number of ions can satisfactorily be explained by isentropic expansion of the shocked material to a particle density of n ≈ 1020 cm-3 whereupon the rate processes in the expanding ion cloudlet govern the residual ionization. In velocity regions where laboratory measurements can be carried out, the agreement between theory and experiment confirms the assumptions made.