Global axisymmetric simulations of photoevaporation and magnetically driven protoplanetary disk winds

TL;DR

This study uses 2D axisymmetric MHD simulations to explore how photoevaporation and magnetic winds interact in protoplanetary disks, revealing the transition conditions and wind morphologies depending on magnetic field strength.

Contribution

It provides the first detailed quantification of the transition between photoevaporative and magnetically driven disk winds in a 2D non-ideal MHD framework.

Findings

Transition between wind types occurs at plasma beta ≥ 10^7.

Magnetically driven winds dominate at stronger magnetic fields.

Outflows become irregular and asymmetric with stronger magnetic fields.

Abstract

Photoevaporation and magnetically driven winds are two independent mechanisms to remove mass from protoplanetary disks. In addition to accretion, the effect of these two principles acting concurrently could be significant and the transition between those two has not been extensively studied and quantified in the literature yet. In order to contribute to the understanding of disk winds, we present the phenomena emerging in the framework of two-dimensional axisymmetric, non-ideal magnetohydrodynamic simulations including EUV-/ X-ray driven photoevaporation. Of particular interest are the examination of the transition region between photoevaporation and magnetically driven wind, the possibility of emerging magneto-centrifugal wind effects, as well as the morphology of the wind itself depending on the strength of the magnetic field. We use the PLUTO code in a 2.5D axisymmetric configuration with additional treatment of EUV-/ X-ray heating and dynamic ohmic diffusion based on a semi-analytical chemical model. We identify the transition between both outflow types to occur for values of the initial plasma beta $\beta \geq 10^7$, while magnetically driven winds generally outperform photoevaporation for stronger fields. In our simulations we observe irregular and asymmetric outflows for stronger magnetic fields. In the weak field regime the photoevaporation rates are slightly lowered by perturbations of the gas density in the inner regions of the disk. Overall, our results predict a wind with a lever arm smaller than 1.5, consistent with a hot magneto-thermal wind. Stronger accretion flows are present for values of $\beta < 10^7$.