The signature of the magnetorotational instability in the Reynolds and Maxwell stress tensors in accretion discs

Martin E. Pessah, Chi Kwan Chan, Dimitrios Psaltis

Research output: Contribution to journalArticlepeer-review

47 Scopus citations

Abstract

The magnetorotational instability is thought to be responsible for the generation of magnetohydrodynamic turbulence that leads to enhanced outward angular momentum transport in accretion discs. Here, we present the first formal analytical proof showing that, during the exponential growth of the instability, the mean (averaged over the disc scaleheight) Reynolds stress is always positive, the mean Maxwell stress is always negative, and hence the mean total stress is positive and leads to a net outward flux of angular momentum. More importantly, we show that the ratio of the Maxwell to the Reynolds stresses during the late times of the exponential growth of the instability is determined only by the local shear and does not depend on the initial spectrum of perturbations or the strength of the seed magnetic field. Even though we derived this property of the stress tensors for the exponential growth of the instability in incompressible flows, numerical simulations of shearing boxes show that this characteristic is qualitatively preserved under more general conditions, even during the saturated turbulent state generated by the instability.

Original languageEnglish (US)
Pages (from-to)183-190
Number of pages8
JournalMonthly Notices of the Royal Astronomical Society
Volume372
Issue number1
DOIs
StatePublished - Oct 2006

Keywords

  • Accretion,accretion discs
  • Black hole physics
  • Instabilities
  • MHD
  • Turbulence

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Fingerprint

Dive into the research topics of 'The signature of the magnetorotational instability in the Reynolds and Maxwell stress tensors in accretion discs'. Together they form a unique fingerprint.

Cite this