Giant Planet Formation

As a young gas giant approaches the mass of Jupiter, its tides becomes strong enough to clear a gap around its orbit in the protoplanetary disk from which it formed. Its subsequent growth depends on the gas flow through the gap. If the gas is sufficiently ionized, it may couple to magnetic fields, which can drive that flow. In \citet{2018arXiv180404265K}, I performed Monte Carlo radiative transfer calculations of the X-rays emitted from a protostar and solved a simplified gas-grain recombination reaction network to determine the ionization state of the gas in planet-opened gaps. I then computed the magnetic diffusivities of the resultant plasma and found that while they were too high to support magneto-rotational turbulence, Hall-shear instability and potentially magneto-centrifugal winds could operate. Importantly, the high diffusivities indicate that the non-ideal terms in the induction equation dominate the evolution of the magnetic field. Three-dimensional magnetohydrodynamic simulations of disks with planet-opened gaps that include these non-ideal terms are necessary to evaluate the evolution of the gas in gaps and its effects on the growth of giant planets.

For more details, check out our paper X-Ray Ionization of Planet-Opened Gaps in Protostellar Disks.