Self-similar accretion flows with convection

被引:338
作者
Narayan, R
Igumenshchev, IV
Abramowicz, MA
机构
[1] Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA
[2] Univ Gothenburg, Inst Theoret Phys, S-41296 Gothenburg, Sweden
[3] Chalmers Univ Technol, S-41296 Gothenburg, Sweden
关键词
accretion; accretion disks; convection; hydrodynamics; turbulence;
D O I
10.1086/309268
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
We consider height-integrated equations of an advection-dominated accretion flow (ADAF), assuming that there is no mass outflow. We include convection through a mixing-length formalism. We seek selfsimilar solutions in which the rotational velocity and sound speed scale as R-1/2, where R is the radius, and consider two limiting prescriptions for the transport of angular momentum by convection. In one limit, the transport occurs down the angular velocity gradient, so convection moves angular momentum outward. In the other, the transport is down the specific angular momentum gradient, so convection moves angular momentum inward. We also consider general prescriptions that lie in between the two limits. When convection moves angular momentum outward, we recover the usual self-similar solution for ADAFs in which the mass density scales as rho proportional to R-3/2. When convection moves angular momentum inward, the result depends on the viscosity coefficient alpha. If alpha > alpha(crit1) similar to 0.05, we once again find the standard ADAF solution. For alpha < alpha(crit2) similar to alpha(crit1), however, we find a nonaccreting solution in which rho proportional to R-1/2. We refer to this as a "convective envelope" solution or a "convection-dominated accretion flow." Two-dimensional numerical simulations of ADAFs with values of alpha less than or similar to 0.03 have been reported by several authors. The simulated ADAFs exhibit convection. By virtue of their axisymmetry, convection in these simulations moves angular momentum inward, as we confirm by computing the Reynolds stress. The simulations give rho proportional to R-1/2, in good agreement with the convective envelope solution. The R-1/2 density profile is not a consequence of mass outflow. The relevance of these axisymmetric low-alpha simulations to real accretion flows is uncertain.
引用
收藏
页码:798 / 808
页数:11
相关论文
共 34 条
  • [1] Solar convection: Comparison of numerical simulations and mixing-length theory
    Abbett, WP
    Beaver, M
    Davids, B
    Georgobiani, D
    Rathbun, P
    Stein, RF
    [J]. ASTROPHYSICAL JOURNAL, 1997, 480 (01) : 395 - 399
  • [2] SLIM ACCRETION DISKS
    ABRAMOWICZ, MA
    CZERNY, B
    LASOTA, JP
    SZUSZKIEWICZ, E
    [J]. ASTROPHYSICAL JOURNAL, 1988, 332 (02) : 646 - 658
  • [3] THERMAL EQUILIBRIA OF ACCRETION DISKS
    ABRAMOWICZ, MA
    CHEN, XM
    KATO, S
    LASOTA, JP
    REGEV, O
    [J]. ASTROPHYSICAL JOURNAL, 1995, 438 (01) : L37 - L39
  • [4] Calibrating the mixing-length parameter for a red giant envelope
    Asida, SM
    [J]. ASTROPHYSICAL JOURNAL, 2000, 528 (02) : 896 - 906
  • [5] Instability, turbulence, and enhanced transport in accretion disks
    Balbus, SA
    Hawley, JF
    [J]. REVIEWS OF MODERN PHYSICS, 1998, 70 (01) : 1 - 53
  • [6] A POWERFUL LOCAL SHEAR INSTABILITY IN WEAKLY MAGNETIZED DISKS .4. NONAXISYMMETRIC PERTURBATIONS
    BALBUS, SA
    HAWLEY, JF
    [J]. ASTROPHYSICAL JOURNAL, 1992, 400 (02) : 610 - 621
  • [7] THICK ACCRETION DISKS - SELF-SIMILAR, SUPERCRITICAL MODELS
    BEGELMAN, MC
    MEIER, DL
    [J]. ASTROPHYSICAL JOURNAL, 1982, 253 (02) : 873 - 896
  • [8] On the fate of gas accreting at a low rate on to a black hole
    Blandford, RD
    Begelman, MC
    [J]. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 1999, 303 (01) : L1 - L5
  • [9] UNIFIED DESCRIPTION OF ACCRETION FLOWS AROUND BLACK-HOLES
    CHEN, XM
    ABRAMOWICZ, MA
    LASOTA, JP
    NARAYAN, R
    YI, I
    [J]. ASTROPHYSICAL JOURNAL, 1995, 443 (02) : L61 - L64
  • [10] Cox J. P., 1968, Principles of Stellar Structure