Rossby wave instability in weakly ionized protoplanetary disks. II. radial B-fields

TL;DR

This study explores how radial magnetic fields and non-ideal MHD effects influence Rossby wave instability in protoplanetary disks, revealing that magnetic fields can significantly alter instability growth rates.

Contribution

It extends previous work by analyzing the impact of radial magnetic fields and non-ideal effects on RWI modes using global linear analysis and spectral methods.

Findings

Radial fields behave similarly to vertical fields in affecting RWI.

Weak radial fields (β ~ 10^3-10^4) significantly reduce growth rates.

Strong non-ideal effects make growth rates resemble hydrodynamic models.

Abstract

Building on our first paper in this series, we investigate the impact of radial magnetic fields and non-ideal magnetohydrodynamic (MHD) effects - specifically, Ohmic resistivity, Hall drift, and ambipolar diffusion - on RWI unstable modes. The presence of a radial field is linked to the disk's vertical shear and vertical magnetic field. We perform radially global linear analyses and utilize the spectral code \textsc{Dedalus} to solve the matrix eigenvalue problems. Our findings reveal that radial fields exhibit behavior similar to vertical fields. In the ideal MHD limit, radial fields enhance the effect of vertical fields in reducing growth rates, with significant reductions starting at relatively weak field strengths, around $\beta \sim 10^3 - 10^4$, which are relevant to protoplanetary disks. In the non-ideal MHD limit, all three non-ideal effects, when sufficiently strong, cause the growth rates to closely resemble those observed in hydrodynamic models.