On the structure of the plasma disk in the Jovian magnetosphere

Abstract

We have determined the structure of the lowenergy plasma disk in the middle Jovian magnetosphere. First, the shape of the dense plasma structures have been described analytically. We have investigated a distribution of the background plasma along the arbitrary magnetic flux tube in the frame of diffuse equilibrium taking into account the action of centrifugal aad gravitational forces. Using the results of this investigation we have shown that background plasma density reaches the maximum on the surface, consisting of the warped disk between the magnetic and centrifugal equators outside lo's orbit and two mirror symmetrical “petals” in the region of the polar cusps. Second, the radial profile of plasma density in the disk has been studied. We have considered the magnetohydrodyoamic stability of the low-latitude dense plasma disk formed under the action of centrifugal force. The equilibrium radial distribution of the plasma was found for the plasma disk at the threshold of the instability with respect to small-scale MHD perturbations. The effect of the inite ion Larmor radius at the threshold of plasma instability was taken into account. We have estimated the iniuence of the inhomogeneity of the plasma perturbations along the magnetic field on the radial density profile bearing in mind the finite conductivity of the Jovian ionosphere. A relationship between the thickness of the plasma disk and the radial plasma distribution has been pointed out. The results obtained were compared with the known experimental data for the Jovian plasma sheet.