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Keywords:

  • accretion, accretion discs;
  • MHD;
  • ISM: jets and outflows

ABSTRACT

The existence of outflows in accretion flows has been confirmed by observations and by magnetohydrodynamics simulations. In this paper, we study the outflows of advection-dominated accretion flows (ADAFs) in the presence of resistivity and a toroidal magnetic field. The mechanism of energy dissipation in the flow is assumed to be the viscosity and the magnetic diffusivity as a result of turbulence in the accretion flow. It is also assumed that the magnetic diffusivity and the kinematic viscosity are not constant and that they vary by position, and the α-prescription is used for these. The influence of outflows emanating from an accretion disc is considered as a sink for mass, angular momentum and energy. The self-similar method is used to solve the integrated equations that govern the behaviour of the accretion flow in the presence of outflows. The solutions represent the disc that rotates faster and becomes cooler for stronger outflows. Moreover, by adding magnetic diffusivity, the surface density and rotational velocity decrease, while the radial velocity and temperature increase. A study of the present model with the magnitude of a magnetic field implies that the disc rotates and accretes faster and becomes hotter, while the surface density decreases. The thickness of the disc increases when adding a magnetic field or resistivity, while the disc becomes thinner for more mass and energy losses resulting from the outflows.