Global Simulations of Protoplanetary Disk Outflows with Coupled Non-ideal Magnetohydrodynamics and Consistent Thermochemistry

Abstract

Magnetized winds may be important in dispersing protoplanetary disks and influencing planet formation. We carry out global full magnetohydrodynamic simulations in axisymmetry, coupled with ray-tracing radiative transfer, consistent thermochemistry, and non-ideal MHD diffusivities. Magnetized models lacking EUV photons (hν > 13.6 eV) feature warm molecular outflows that have typical poloidal speeds 4 km s −1 . When the magnetization is sufficient to drive accretion rates ∼ 10 −8 M yr −1 , the wind mass-loss rate is comparable. Such outflows are driven not centrifugally but by the pressure of toroidal magnetic fields produced by bending the poloidal field. Both the accretion and outflow rates increase with the poloidal field energy density, the former almost linearly. The mass-loss rate is also strongly affected by ionization due to UV and X-ray radiation near the wind base. Adding EUV irradiation to the system heats, ionizes, and accelerates the part of the outflow nearest the symmetry axis, but reduces the overall mass-loss rate by exerting pressure on the wind base. Most of our models are non-turbulent, but some with reduced dust abundance and therefore higher ionization fractions exhibit magnetorotational instabilities near the base of the wind.

Dispersal of protoplanetary discs by the combination of magnetically driven and photoevaporative winds

“…Recently Wang et al (2019) have performed the global radiation magnetohydrodynamic simulations for the first time.…”

Global axisymmetric simulations of photoevaporation and magnetically driven protoplanetary disk winds

“…They reported that by applying an increasingly strong magnetic field on a purely thermal disk wind, a transition from magnetic pressure driven to magneto-centrifugally driven winds is to be expected. Very recently, Wang et al (2019) introduced a consistent thermochemical model to the framework of Bai (2017). In contrast to the simulations performed here, no wide plasma parameter sweep was conducted.…”

Global Simulations of the Vertical Shear Instability with Nonideal Magnetohydrodynamic Effects

“…As mentioned earlier, we aim to conduct relatively clean numerical experiments, hence our disk model is 1 The VSI primarily occurs in the disk where gas is molecular with γ = 7/5. By a transition above the disk surface, the gas is mainly atomic in the wind zone where γ = 5/3 (e.g., Wang et al 2019). The exact value of γ affects the critical thermal relaxation timescale to trigger the VSI (Lin & Youdin 2015).…”

“…Global non-ideal MHD simualtions coupled with thermochemistry performed on disk winds indicate a τ ∼ 5 in the atmosphere(Wang et al 2019). More realistic thermodynamic prescription can be applied to the wind zone in the future work.…”