http://arxiv.org/abs/1402.7102
The gas dynamics of protoplanetary disks (PPDs) is largely controlled by non-ideal magnetohydrodynamic (MHD) effects including Ohmic resistivity, Hall effect and ambipolar diffusion, among which the role of Hall effect is the least explored and most poorly understood. In this series, we have included all three non-ideal MHD effects in a self-consistent manner to investigate the role of Hall effect on the PPD gas dynamics using local shearing-box simulations. In this first paper, we focus on the inner region of PPDs where previous studies without including the Hall effect have revealed that the inner disk up to ~10 AU is largely laminar with accretion driven by magnetocentrifugal wind. We confirm this basic picture and show that the Hall effect introduces modest modifications to the wind solutions, depending on the polarity of the large scale poloidal magnetic field B_0 threading the disk. When B_0.Omega>0, horizontal magnetic field is further amplified, leading to stronger disk wind (by ~50% or less in terms of wind-driven accretion rate). The enhanced horizontal field also leads to much stronger large-scale Maxwell stress that contributes to a considerable fraction of the wind-driven accretion rate. When B_0.Omega<0, horizontal magnetic field is reduced, leading to weaker disk wind (by ~20%). More importantly, we find that when B_0.Omega>0, the range of stability is enlarged, and one expects the laminar region to extend further to ~15 AU before the magneto-rotational instability sets in, while for B_0.Omega<0, the laminar region extends only to ~3 AU for typical PPD accretion rates. Scaling relations for the wind properties, especially wind-driven accretion rate are provided for aligned and anti-aligned field geometries. Implications for global disk evolution and planet formation are also briefly discussed.
X. Bai
Mon, 3 Mar 14
41/55