ON THE STRUCTURE OF THE PLASMA DISK IN THE JOVIAN MAGNETOSPHERE

We have determined the structure of the low-energy plasma disk in the middle Jovian magnetosphere. First, the shape of the dense plasma stru ctures have been described analytically. We have investigated a distri bution of the background plasma along the arbitrary magnetic flux tube in the frame of diffuse equilibrium taking into account the action of centrifugal and gravitational forces. Using the results of this inves tigation we have shown that background plasma density reaches the maxi mum on the surface, consisting of the warped disk between the magnetic and centrifugal equators outside Io's orbit and two mirror symmetrica l ''petals'' in the region of the polar cusps. Second, the radial prof ile of plasma density in the disk has been studied. We have considered the magnetohydrodynamic stability of the low-latitude dense plasma di sk formed under the action of centrifugal force. The equilibrium radia l distribution of the plasma was found for the plasma disk at the thre shold of the instability with respect to small-scale MHD perturbations . The effect of the finite ion Larmor radius at the threshold of plasm a instability was taken into account. We have estimated the influence of the inhomogeneity of the plasma perturbations along the magnetic fi eld on the radial density profile bearing in mind the finite conductiv ity of the Jovian ionosphere. A relationship between the thickness of the plasma disk and the radial plasma distribution has been pointed ou t. The results obtained were compared with the known experimental data for the Jovian plasma sheet.