Steady-State Solutions for a Geometrically Thin Accretion Disk with Magnetically-Driven Winds

TL;DR

This paper develops steady-state models of geometrically thin accretion disks with magnetically-driven winds, revealing how winds alter spectral properties and proposing observational tests for wind detection.

Contribution

It introduces a comprehensive magnetohydrodynamic model of thin accretion disks with winds, analyzing spectral signatures and providing a method to observationally identify wind presence.

Findings

Spectral slope changes indicate wind presence.

Mass accretion rate decreases inward, mass loss increases with radius.

Wind makes the spectrum deviate from the standard /3 power-law.

Abstract

We present steady-state solutions for a one-dimensional, magnetically-driven accretion disk wind model based on magnetohydrodynamic equations. We assume a geometrically thin, gas-pressure-dominated accretion disk, incorporating both magnetic braking and turbulent viscosity introduced by an extended alpha-viscosity prescription. Additionally, the vertical stress parameter is assumed to scale with the disk aspect ratio. We confirm that the derived solutions result in standard disk solutions when the wind is absent. We find that the mass accretion rate decreases as the disk mass falls inward, while the mass loss rate increases with radius. The disk spectrum emitted from the magnetically-driven disk wind can be observed without interference from the wind medium because the wind is significantly optically thin. The spectral luminosity is proportional to $\nu^{1/3}$ in the intermediate, multicolor-blackbody wavebands, in the absence of wind, as predicted by standard disk theory. However, in the presence of wind, it follows a different power-law dependence on frequency over the same range. A deviation from the spectral slope of $1/3$, particularly a negative spectral slope, is a clear indicator of the presence of a magnetically driven wind. We also discuss an observational strategy to test our model with multi-wavelength observations.