Turbulence and Angular Momentum Transport in Accreting Magnetized Disks

Abstract

Accretion is a fundamental process for many astrophysical objects and the associated release of gravitational energy can power some of the most energetic phenomena in the universe. Accretion mainly occurs in the form of a disk and a basic problem of the theory is to determine how the material in the disc can effectively accrete losing its angular momentum. This process of angular momentum transport in the accretion disk is currently interpreted as the result of magnetohydrodynamical turbulence driven by the magnetorotational instability. Recent results have however questioned the effectiveness of such mechanism, showing a decrease of the transport with the increase of the Reynolds number, leading to the possible conclusion that in astrophysical conditions it cannot explaine the needed angular momentum transport. With this project, by using numerical simulations of unprecedented resolution and accuracy and introducing the new effect of stratification. we aim at answering the crucial question whether there is a universal regime of magnetorotational turbulence, whose properties are independent of dissipation and external condition and whether the resulting transport is effectively of astrophysical significance.