English

Self-similar structure of magnetized ADAFs and CDAFs

Astrophysics 2015-05-13 v1

Abstract

(Abridged) We study the effects of a global magnetic field on viscously-rotating and vertically-integrated accretion disks around compact objects using a self-similar treatment. We extend Akizuki & Fukue's work (2006) by discussing a general magnetic field with three components (r,ϕ,zr, \phi, z) in advection-dominated accretion flows (ADAFs). We also investigate the effects of a global magnetic field on flows with convection. For these purposes, we first adopt a simple form of the kinematic viscosity ν=αcs2/ΩK\nu=\alpha c_{s}^{2}/\Omega_{K} to study magnetized ADAFs. Then we consider a more realistic model of the kinematic viscosity ν=αcsH\nu=\alpha c_{s}H, which makes the infall velocity increase but the sound speed and toroidal velocity decrease. We next use two methods to study magnetized flows with convection, i.e., we take the convective coefficient αc\alpha_{c} as a free parameter to discuss the effects of convection for simplicity. We establish the αcα\alpha_{c}-\alpha relation for magnetized flows using the mixing-length theory and compare this relation with the non-magnetized case. If αc\alpha_{c} is set as a free parameter, then vr|v_{r}| and csc_{s} increase for a large toroidal magnetic field, while vr|v_{r}| decreases but vϕ|v_{\phi}| increases (or decreases) for a strong and dominated radial (or vertical) magnetic field with increasing αc\alpha_{c}. In addition, the magnetic field makes the αcα\alpha_{c}-\alpha relation be distinct from that of non-magnetized flows, and allows the ρr1\rho\propto r^{-1} or ρr2\rho\propto r^{-2} structure for magnetized non-accreting convection-dominated accretion flows with α+gαc<0\alpha+g\alpha_{c}< 0 (where gg is the parameter to determine the condition of convective angular momentum transport).

Keywords

Cite

@article{arxiv.0805.3254,
  title  = {Self-similar structure of magnetized ADAFs and CDAFs},
  author = {Dong Zhang and Z. G. Dai},
  journal= {arXiv preprint arXiv:0805.3254},
  year   = {2015}
}

Comments

22 pages, 5 figures, Accepted for publication in MNRAS

R2 v1 2026-06-21T10:42:50.746Z