Conditions of excitation of magnetospheric convection by the electric current generated in the bow shock

Abstract

This paper analyzes the consequences of electric current generation at the front of the Bow Shock (BS) and the dependence of the direction of this current on the IMF. The conditions of this current closure through the body of the magnetosphere are discussed. It is shown that the process of penetration of the external current into magnetized plasma has a two-stage character. Initially, a change in current on the boundary gives rise to a region of surface charge, the field of which polarizes the near-wall layer with the thickness on the order of one gyroradius of protons. The polarization process involves the formation of the displacement current which produces the Ampere force accelerating the plasma inside the double layer. When the plasma velocity reaches the electric drift velocity (within a time on the order of the inverse gyrofrequency of protons), the electric field in this plasma disappears, whereas in a fixed frame of reference, on the contrary, it reaches equilibrium values. The front of variation of the electric field penetrates the plasma with the velocity of a fast magnetosonic wave. A change in the convection velocity field causes a redistribution of plasma pressure. The appearance of corresponding gradients signifies the penetration of current into plasma. The gradients are changing until a new steady state is reached, to which the new convection velocity field and the new plasma pressure field correspond. This new state is reached in a time which is estimated.