Structure of advection-dominated accretion flows (ADAFs) with outflows: the role of toroidal magneti

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  The main aim of this article is to verify the structure of advection-dominated accretion flows(ADAFs)along the θ direction when bathed in a toroidal magnetic field.We use spherical coordinates to solve our equation.All three components of the velocity field are present in our work.We reduce the equations to a set of differential equations in q and apply a symmetric boundary condition at the equatorial plane of the disc.The results have shown that the vertical structure of the disc is significantly affected by the magnetic field and its corresponding resistivity.By considering a self-similar solution along the radial direction,proper boundary conditions and reflection symmetry in the equatorial plane of the disc,we have constructed the structure of the disc along the θ direction explicitly.We have shown that only by assuming vθ≠0 do the solutions represent an inflow–outflow behavior that is not reported in previous ADAF investigations.This assumption improved the solution of Narayan & Yi 1995 to interpret the existence of outflows in hot accreting systems.Our disc consists of three different regions.1.The predominant region,called the inflow region.It extends from mid-plane to the place where the radial velocity is equal to zero,vr(θ0)= 0,and contains the largest portion of the mass.2.An outflow region,which is located just after the inflow region and continues to the surface of the disc,in which matter starts escaping the central accretor in the r direction.3.The third region,called the wind region.This region contains material blowing out from the boundary of the outflow region.An area with very low width.Compared with the non-magnetic field solution(Jiao & Wu 2011),the existence of a magnetic field and its resistivity in our case can produce more advective energy.Also,the B-field configuration can affect energy transportation along accretion discs.In this article we used two parameters β0 and η0 in order to study the effect of a magnetic field on the vertical structure of the disc.Our results showed that magnetic pressure will increase if changes on moving towards the surface of disc.Also,if we increase the β0 parameter(which represents the ratio of gas pressure to field pressure at θ= 90°)it will enhance the rate of magnetic pressure growth.Moreover,it was demonstrated that the discs half width declines as β0 increases.
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