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    Toroidal LNRF-velocity profiles in thick accretion discs orbiting rapidly rotating Kerr black holes

    Zdeněk Stuchlík · Listopad 01, 2006 · Fyzika · 0 comments
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    Publication date: Nov 2006

    Abstract:
    We show that in the equatorial plane of marginally stable thick discs
    (with uniformly distributed specific angular momentum l(r, θ) =
    const) the orbital velocity relative to the LNRF has a positive radial
    gradient in the vicinity of black holes with a > 0.99979. The change
    of sign of the velocity gradient occurs just above the center of the
    thick toroidal discs, in the region where stable circular geodesics of
    the Kerr spacetime are allowed. The global character of the phenomenon
    is given in terms of topology changes of the von Zeipel surfaces
    (equivalent to equivelocity surfaces in the tori with l(r, θ) =
    const). Toroidal von Zeipel surfaces exist around the circle
    corresponding to the minimum of the equatorial LNRF velocity profile,
    indicating a possibility of development of some vertical instabilities
    in those parts of marginally stable tori with positive gradient of the
    LNRF velocity. Eventual oscillatory frequencies connected with the
    phenomenon are given in a coordinate-independent form.

    Authors:
    Stuchlík, Zdeněk; Slaný, Petr; Török, Gabriel;

    http://adsabs.harvard.edu/abs/2006AIPC..861..778S

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