Open AccessAccretion disc viscosity: how big is alpha?
Author(s) -
King A. R.,
Pringle J. E.,
Livio M.
Publication year - 2007
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2007.11556.x
Subject(s) - physics , astrophysics , accretion (finance) , accretion disc , viscosity , range (aeronautics) , observational study , ionization , astronomy , statistics , thermodynamics , ion , materials science , quantum mechanics , composite material , mathematics
We consider observational and theoretical estimates of the accretion disc viscosity parameter α. We find that in thin, fully ionized discs, the best observational evidence suggests a typical range α∼ 0.1–0.4, whereas the relevant numerical simulations tend to derive estimates for α which are an order of magnitude smaller. We discuss possible reasons for this apparent discrepancy.