The Jovian magnetodisk

Magnetic field measurements made by the vector helium magnetometers on board Pioneers-10 and 11 reveal the existance of a current sheet (thickness approximately 2Rsub(J)) carrying an eastward current. Self-consistent studies of the current sheet show that the magnitude of the current is of the order of 10-2 Am-1 and that the current is carried by a hot (T>1 keV) plasma, the density of which varies between 1 cm-3 at 30Rsub(J) to 10-2 cm-3 at 80 Rsub(J). The current sheet is warped azimuthally and parallel to the magnetic dipole equator. The existence of an azimuthal field component indicates a poloidal plasma flow transporting some 1029 ions per second from Jupiter into the outer magnetosphere. It is shown that, if the outer magnetosphere is in a steady state, this plasma must be transported outward within the current sheet by a diffusion process which is faster than the one responsible for particle transport in the inner magnetosphere but slower than Bohm diffusion. It is suggested that the diffusion is due to the observed MHD turbulence in the current sheet. Such a model requires the existence of open field lines along which particles can escape freely into interplanetary space. (Auth.)