Self-similar structure of resistive ADAFs with outflow and large-scale magnetic field

Abstract

The observations and simulations have revealed that large-scale magnetic field and outflows can exist in the inner regions of an advection-dominated accretion disc where the resistive diffusion may also be important. In the present paper, the roles of large-scale magnetic field and outflows in the structure of resistive advection-dominated accretion discs are explored by assuming that the accretion flow is radially self-similar. In the non-ideal magnetohydrodynamic (MHD) approximation, the results show that the angular velocity is always sub-Keplerian when both the outflow and the large-scale magnetic field are taken into account. A stronger toroidal field component leads to faster rotation, while the disc rotates with faster rate if the vertical field component is weaker. The increase of magnetic diffusivity causes the infall velocity to be close to Keplerian velocity. Although the previous studies in the ideal MHD approximation have shown that the disc temperature decreases due to the vertical field component, we find that the effect of vertical field component on the temperature of a resistive disc depends on the magnetic diffusivity. When the magnetic diffusivity is high, the more efficient mechanism for decreasing the disc temperature can be the outflows, and not the large-scale magnetic field. In such a limit of the magnetic diffusivity, the components of the large-scale magnetic field enhance the gas temperature. The increase of temperature can lead to heating and acceleration of the electrons and help us to explain the origin of phenomena such as the flares in Sgr A*. On the other hand, the infall velocity in such a limit rises as the temperature increases, and therefore the surface density falls to too low values. Any change in the density profile can alter the structure and the emitted spectrum of disc.

Resistive Hot Accretion Flows with Anisotropic Pressure

“…( 19)). These results are in excellent agreement with previous work (e.g., Zhang and Dai 2008;Ghoreyshi and Shadmehri 2020;Ghoreyshi 2020). Now, we explore the effects of s on the physical variables of hot accretion flows when η 0 = 0.1.…”

“…Previous work showed that in the ideal MHD the vertical component of the magnetic field reduces the velocities discussed in this paper (e.g., Mosallanezhad et al 2013). However, the effect of the vertical field component on the resistive disks structure depends on the magnetic diffusivity (Ghoreyshi 2020). Then accounting for this component may yield different results.…”

“…Abbassi and Mosallanezhad (2012) also showed that the rotational velocity of the resistive accretion flows in the absence of outflow depends on the magnetic diffusivity. They found that the effect of magnetic diffusivity on the rotational velocity depends on the field components (see also Ghoreyshi 2020). In the presence of outflows, the results indicate that the rotational velocity of hot accretion flows is always sub-Keplerian and the disk reaches a non-rotating limit when the magnetic diffusivity increases (Ghoreyshi 2020).…”

“…They found that the effect of magnetic diffusivity on the rotational velocity depends on the field components (see also Ghoreyshi 2020). In the presence of outflows, the results indicate that the rotational velocity of hot accretion flows is always sub-Keplerian and the disk reaches a non-rotating limit when the magnetic diffusivity increases (Ghoreyshi 2020). We know that the magnetic diffusivity not only modifies the structure of accretion flows, but also can affect wind lunching and the strength of the disk wind (Kuwabara et al 2000;Fendt and Čemeljić 2002;Igumenshchev et al 2003;Čemeljić et al 2014;Qian et al 2018;Vourellis et al 2019).…”

“…By considering a relatively strong magnetic field, found that the infall velocity increases with the anisotropic pressure and with the outflows. We know that the changes in the infall velocity due to the outflow are dependent on the magnetic diffusivity when the anisotropic pressure is absent (Ghoreyshi 2020). To the best of our knowledge, the effect of magnetic diffusivity on the properties of hot accretion flows with the anisotropic pressure has not yet been studied in detail.…”