Angular momentum transport in accretion disk boundary layers around weakly magnetized stars

Martin E. Pessah, Chi Kwan Chan

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

The standard model for turbulent shear viscosity in accretion disks is based on the assumption that angular momentum transport is opposite to the radial angular frequency gradient of the disk. This implies that the turbulent stress must be negative and thus transport angular momentum inwards, in the boundary layer where the accretion disk meets the surface of a weakly magnetized star. However, this behavior is not supported by numerical simulations of turbulent magnetohydrodynamic (MHD) accretion disks, which show that angular momentum transport driven by the magnetorotational instability (MRI) is inefficient in disk regions where, as expected in boundary layers, the angular frequency increases with radius. Motivated by the need of a deeper understanding of the behavior of an MHD fluid in a differentially rotating background that deviates from a Keplerian profile, we study the dynamics of MHD waves in configurations that are stable to the standard MRI. Employing the shearing-sheet framework, we show that transient amplification of shearing MHD waves can generate magnetic energy without leading to a substantial generation of hydromagnetic stresses. While these results are in agreement with numerical simulations, they emphasize the need to better understand the mechanism for angular momentum transport in the inner disk regions on more solid grounds.

Original languageEnglish (US)
Title of host publicationInstabilities and Structures in Proto-Planetary Disks, ISPP 2012
DOIs
StatePublished - 2013
Externally publishedYes
EventWorkshop on Instabilities and Structures in Proto-Planetary Disks, ISPP 2012 - Marseille, France
Duration: Sep 17 2012Sep 20 2012

Publication series

NameEPJ Web of Conferences
Volume46
ISSN (Print)2101-6275
ISSN (Electronic)2100-014X

Conference

ConferenceWorkshop on Instabilities and Structures in Proto-Planetary Disks, ISPP 2012
Country/TerritoryFrance
CityMarseille
Period9/17/129/20/12

ASJC Scopus subject areas

  • Physics and Astronomy(all)

Fingerprint

Dive into the research topics of 'Angular momentum transport in accretion disk boundary layers around weakly magnetized stars'. Together they form a unique fingerprint.

Cite this