Bifurcation of the tail current sheet in Jovian magnetosphere

摘要

Multiple crossings of the magnetotail current sheet by a single spaceraft give possibility to distinguish between two types of electric current density distribution: single-peaked (Harris type current layer) and double-peaked (bifurcated current sheet). Magnetic field measurements in Jovian magnetic tail by Voyager-2 and Galileo reveal the bifurcation of tail current sheet. Electric current density possesses minimum at the point of B_x-component reversal and two maxima at the distance where the magnetic field strength reaches 50% of its value in the tail lobe. Solution for self-consistent magnetic field in the geomagnetic tail is obtained in a simple model. We arrive at the conclusion that the bifurcated current sheet with two maxima of the electric current density is an equilibrium state of the geomagnetic tail when ion pressure is anisotropic in the plane perpendicular to the magnetic field.