including hot plasma pressure anisotropy

摘要

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 ～20 R_J and outward of ～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 ～1.2 and ～2.7° 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 β_(h‖e) ?β_(h⊥e) ?1?2, for K_h =2.0?2.5 × 10~7 Pa m T~(?1). For larger values of K_h, β_(h‖e)?β_(h⊥e) exceeds 2 near ～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.