Instability of warped discs

Küçük Resim Yok

Tarih

2018

Dergi Başlığı

Dergi ISSN

Cilt Başlığı

Yayıncı

Oxford University Press

Erişim Hakkı

info:eu-repo/semantics/closedAccess

Özet

Accretion discs are generally warped. If a warp in a disc is too large, the disc can 'break' apart into two or more distinct planes, with only tenuous connections between them. Further, if an initially planar disc is subject to a strong differential precession, then it can be torn apart into discrete annuli that precess effectively independently. In previous investigations, torquebalance formulae have been used to predict where and when the disc breaks into distinct parts. In this work, focusing on discs with Keplerian rotation and where the shearing motions driving the radial communication of the warp are damped locally by turbulence (the 'diffusive' regime), we investigate the stability of warped discs to determine the precise criterion for an isolated warped disc to break. We find and solve the dispersion relation, which, in general, yields three roots. We provide a comprehensive analysis of this viscous-warp instability and the emergent growth rates and their dependence on disc parameters. The physics of the instability can be understood as a combination of (1) a term that would generally encapsulate the classical Lightman-Eardley instability in planar discs (given by ?(v?)/?? < 0) but is heremodified by the warp to include ?(v1|?|)/?|?| < 0, and (2) a similar condition acting on the diffusion of the warp amplitude given in simplified form by ?(v2|?|)/?|?| < 0. We discuss our findings in the context of discs with an imposed precession, and comment on the implications for different astrophysical systems. © 2018 The Author(s).

Açıklama

Anahtar Kelimeler

Accretion, Accretion discs, Black hole physics, Hydrodynamics, Instabilities

Kaynak

Monthly Notices of the Royal Astronomical Society

WoS Q Değeri

Scopus Q Değeri

Q1

Cilt

476

Sayı

2

Künye