Laboratory and numerical simulations of the impulsive penetration mechanism

Plasma interaction at the interface between the magnetosheath and magnetosphere has been extensively studied during recent years. As a consequence various theoretical models have emerged. The impulsive penetration mechanism initially proposed by Lemaire and Roth as an alternative approach to the steady state reconnection, is a non-stationary model describing the processes which take place when a 3-D solar wind plasma irregularity interacts with the outer regions of the Earth's magnetosphere. In this paper we are reviewing the main features of the impulsive penetration mechanism and the role of the electric field in driving impulsive events. An alternative point of view and the controversy it has raised are discussed. We also review the numerical codes developed to simulate the impulsive transport of plasma across the magnetopause. They have illustrated the relationship between the magnetic field distribution and the convection of solar-wind plasma inside the magnetosphere and brought into perspective non-stationary phenomena (like instabilities and waves) which were not explicitly integrated in the early models of impulsive penetration. Numerical simulations devoted to these processes cover a broad range of approximations, from ideal MHD to hybrid and kinetic codes. The results show the limitation of these theories in describing the full range of phenomena observed at the magnetopause and magnetospheric boundary layers.