One of the great challenges in the study of planetary interiors is to understand the generation of magnetic fields in the interiors of the giant gas planets. Wieland Dietrich and Chris Jones from the University of Leeds have been addressing this problem through high resolution magnetohydrodynamic models, with the novel feature of incorporating realistic radially-dependent profiles for the electrical conductivity (Icarus 305 (2018) 15-32). This allows the study of a range of models in which the conductivity ranges from Jupiter-like, with only a thin outer non-conducting shell to Saturn-like, with a thick non-conducting shell. They find Jupiter-like steady dipolar fields, quadrupolar dynamos for profiles between those of Jupiter and Saturn, and dipolar fields again for Saturn-like profiles. The non-axisymmetric components of the Saturn model are, though, more pronounced than in Saturn itself, prompting the suggestion that a stably stratified region – postulated to exist in Saturn, but not yet incorporated in the model – may be of significance.
Figure 3: The figure shows (from left to right) time-averaged meridional sections of the azimuthal flow, meridional stream function, kinetic helicity, radial and azimuthal magnetic fields; the right hand plots are typical snapshots of the radial field and azimuthal flow at the surface. The top row is for the case of uniform electrical conductivity; the bottom row is for a Jupiter-like profile, in which the electrical conductivity drops off sharply at 90% of the planetary radius.
