On the saturation of the magnetorotational instability via parasitic modes

Martin E. Pessah, Jeremy Goodman

Research output: Contribution to journalArticle

57 Scopus citations

Abstract

We investigate the stability of incompressible, exact, non-ideal magnetorotational (MRI) modes against parasitic instabilities. Both Kelvin-Helmholtz and tearing-mode parasitic instabilities may occur in the dissipative regimes accessible to current numerical simulations. We suppose that a primary MRI mode saturates at an amplitude such that its fastest parasite has a growth rate comparable to its own. The predicted alpha parameter then depends critically on whether the fastest primary and parasitic modes fit within the computational domain and whether non-axisymmetric parasitic modes are allowed. Hence, even simulations that resolve viscous and resistive scales may not saturate properly unless the numerical domain is large enough to allow the free evolution of both MRI and parasitic modes. To minimally satisfy these requirements in simulations with vertical background fields, the vertical extent of the domain should accommodate the fastest growing MRI mode while the radial and azimuthal extents must be twice as large. The fastest parasites have horizontal wavelengths roughly twice as long as the vertical wavelength of the primary.

Original languageEnglish (US)
Pages (from-to)L72-L76
JournalAstrophysical Journal
Volume698
Issue number1 PART 2
DOIs
StatePublished - 2009

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Keywords

  • Accretion
  • Accretion disks
  • Black hole physics
  • Instabilities
  • MHD
  • Turbulence

Fingerprint Dive into the research topics of 'On the saturation of the magnetorotational instability via parasitic modes'. Together they form a unique fingerprint.

  • Cite this