Blog Post 19, Free Form, Astrobites: Accretion Modes

Figure 2 of Ohsuga and Mineshige 2011: Time-averaged structure of the three models produced by the simulations. The shaded regions show the normalized density of inflowing gas. The thick lines are streamlines for the outflows. (This plot is illustrative: the simulations are in two dimensions, not three, and only calculated on one side of the equator.)

In previous free form posts we have mentioned quasars, and other black holes that consume matter through accretion. Let's take a closer look at this process with some cutting edge research. Guest Author Warrick Ball wrote a nice summary of a paper titled "Global structure of three distinct accretion flows and outflows around black holes through two-dimensional radiation-magnetohydrodynamic simulations"published by Ken Ohsuga and Shin Mineshige of the National Astronomical Observatory of Japan and Graduate of Advanced Study.  Here is a summary of that summary.  

A brief over view of accretion is that it is the process by which black holes consume matter by drawing it in.  Usually this matter is comes dust, but it also can be stars, planets, and other black holes in a cosmic food chain that is governed but the principle: "Survival of the Biggest".  

Ohsuga and Mineshige's paper addresses the energy flow and matter flow of accreting matter.  They created a computer simulation of a non-rotating black hole and placed a "doughnut" of gaseous matter around it.  The performed the simulation with gas densities of \(1, 10^(-4), \text{and} 10^{-8} g/cm^3\).  The results were wildly different every time, but seemed to conform to theoretical models fairly well, but not perfectly.  Clearly we still have plenty of work to do in this field.  Some simplifications in the model were simulating a stationary, non-rotating black hole, only simulating one half of the balks hole's equator, and using a 2D model.  This vastly simplifies the simulation and saves on the programming time and computing power needed to execute it.

Source:

http://astrobites.org/2011/06/05/the-many-modes-of-black-hole-accretion/