2013/08/31 by Yuki Io, Takeru K. Suzuki
Physics and Astronomy · #Accretion (finance) #Amplitude #Astrophysical Phenomena and Observations #Astrophysics and Star Formation Studies #Instability #Isothermal process #Magnetohydrodynamic drive #Magnetohydrodynamics #Magnetorotational instability #Poynting vector #Pressure gradient #Solar and Space Plasma Dynamics #Turbulence #astro-ph.EP #astro-ph.HE #astro-ph.SR
paper · pdf · doi:10.1088/0004-637x/780/1/46
14 pages, 14 figures, ApJ, in press, comments welcome
arxiv created 2013/10/30 · openalex publication_date 2013/12/11 · arxiv updated 2015/06/17 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We investigate the formation of hot coronae and vertical outflows in accretion disks by magnetorotational turbulence. We perform local three-dimensional magnetohydrodynamical (MHD) simulations with the vertical stratification by explicitly solving an energy equation with various effective ratios of specific heats, γ. Initially imposed weak vertical magnetic fields are effectively amplified by magnetorotational instability and winding caused by the differential rotation. In the isothermal case (γ = 1), the disk winds are driven mainly by the Poynting flux associated with the MHD turbulence and show quasi-periodic intermittency. In contrast, in the non-isothermal cases with γ ⩾ 1.1, the regions above 1–2 scale heights from the midplane are effectively heated to form coronae with temperature ∼50 times the initial value, which are connected to the cooler midplane region through the pressure-balanced transition regions. As a result, the disk winds are driven mainly by the gas pressure, exhibiting more time-steady nature, although the nondimensional time-averaged mass loss rates are similar to that of the isothermal case. Sound-like waves are confined in the cool midplane region in these cases, and the amplitude of the density fluctuations is larger than that of the isothermal case.