Global Properties of Fully Convective Accretion Disks from Local Simulations

TL;DR

This paper develops a method to derive global properties of fully convective accretion disks by combining local simulation solutions with analytical models, revealing how disk quantities scale with radius.

Contribution

It introduces a two-step approach to connect local simulation data with global disk properties, especially for fully convective disks, using symmetry and scaling relations.

Findings

Method for deriving global disk properties from local simulations.

Scaling relations for disk quantities with radius.

Application to fully convective accretion disks.

Abstract

We present an approach to deriving global properties of accretion disks from the knowledge of local solutions derived from numerical simulations based on the shearing box approximation. The approach consists of a two-step procedure. First a local solution valid for all values of the disk height is constructed by piecing together an interior solution obtained numerically with an analytical exterior radiative solution. The matching is obtained by assuming hydrostatic balance and radiative equilibrium. Although in principle the procedure can be carried out in general, it simplifies considerably when the interior solution is fully convective. In these cases, the construction is analogous to the derivation of the Hayashi tracks for protostars. The second step consists of piecing together the local solutions at different radii to obtain a global solution. Here we use the symmetry of the solutions with respect to the defining dimensionless numbers--in a way similar to the use of homology relations in stellar structure theory--to obtain the scaling properties of the various disk quantities with radius.