A model of force balance in Jupiter's magnetodisc including hot plasma pressure anisotropy

We present an iterative vector potential model of force balance in Jupiter's magnetodisc that includes the effects of hot plasma pressure anisotropy. The fiducial model produces results that are consistent with Galileo magnetic field and plasma data over the whole radial range of the model. The hot plasma pressure gradient and centrifugal forces dominate in the regions inward of similar to 20 R-J and outward of similar to 50 R-J, respectively, while for realistic values of the pressure anisotropy, the anisotropy current is either the dominant component or at least comparable with the hot plasma pressure gradient current in the region in between. With the inclusion of hot plasma pressure anisotropy, the similar to 1.2 and similar to 2.7 degrees shifts in the latitudes of the main oval and Ganymede footprint, respectively, associated with variations over the observed range of the hot plasma parameter K-h, which is the product of hot pressure and unit flux tube volume, are comparable to the shifts observed in auroral images. However, the middle magnetosphere is susceptible to the firehose instability, with peak equatorial values of beta(h parallel to e) - beta(h perpendicular to e) similar or equal to 1-2, for K-h = 2.0-2.5 x 10(7) Pa m T-1. For larger values of K-h, beta(h parallel to e)-beta(h perpendicular to e) exceeds 2 near similar to 25 R-J and the model does not converge. This suggests that small-scale plasmoid release or drizzle of iogenic plasma may often occur in the middle magnetosphere, thus forming a significant mode of plasma mass loss, alongside plasmoids, at Jupiter.