# Nonlinear dynamics of accretion disks with stochastic viscosity

## Abstract

We present a nonlinear numerical model for a geometrically thin accretion disk with the addition of stochastic nonlinear fluctuations in the viscous parameter. These numerical realizations attempt to study the stochastic effects on the disk angular momentum transport. We show that this simple model is capable of reproducing several observed phenomenologies of accretion-driven systems. The most notable of these is the observed linear rms-flux relationship in the disk luminosity. This feature is not formally captured by the linearized disk equations used in previous work. A Fourier analysis of the dissipation and mass accretion rates across disk radii show coherence for frequencies below the local viscous frequency. This is consistent with the coherence behavior observed in astrophysical sources such as Cygnus X-1.

- Authors:

- Harvard-Smithsonian Center for Astrophysics, Cambridge, MD 02138 (United States)
- Joint Space-Science Institute (JSI), College Park, MD 20742 (United States)

- Publication Date:

- OSTI Identifier:
- 22365265

- Resource Type:
- Journal Article

- Resource Relation:
- Journal Name: Astrophysical Journal; Journal Volume: 791; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ACCRETION DISKS; ANGULAR MOMENTUM; ASTROPHYSICS; COMPUTERIZED SIMULATION; EQUATIONS; FLUCTUATIONS; FOURIER ANALYSIS; GALAXIES; LUMINOSITY; MASS; NONLINEAR PROBLEMS; STOCHASTIC PROCESSES; VISCOSITY

### Citation Formats

```
Cowperthwaite, Philip S., and Reynolds, Christopher S., E-mail: pcowpert@cfa.harvard.edu.
```*Nonlinear dynamics of accretion disks with stochastic viscosity*. United States: N. p., 2014.
Web. doi:10.1088/0004-637X/791/2/126.

```
Cowperthwaite, Philip S., & Reynolds, Christopher S., E-mail: pcowpert@cfa.harvard.edu.
```*Nonlinear dynamics of accretion disks with stochastic viscosity*. United States. doi:10.1088/0004-637X/791/2/126.

```
Cowperthwaite, Philip S., and Reynolds, Christopher S., E-mail: pcowpert@cfa.harvard.edu. Wed .
"Nonlinear dynamics of accretion disks with stochastic viscosity". United States.
doi:10.1088/0004-637X/791/2/126.
```

```
@article{osti_22365265,
```

title = {Nonlinear dynamics of accretion disks with stochastic viscosity},

author = {Cowperthwaite, Philip S. and Reynolds, Christopher S., E-mail: pcowpert@cfa.harvard.edu},

abstractNote = {We present a nonlinear numerical model for a geometrically thin accretion disk with the addition of stochastic nonlinear fluctuations in the viscous parameter. These numerical realizations attempt to study the stochastic effects on the disk angular momentum transport. We show that this simple model is capable of reproducing several observed phenomenologies of accretion-driven systems. The most notable of these is the observed linear rms-flux relationship in the disk luminosity. This feature is not formally captured by the linearized disk equations used in previous work. A Fourier analysis of the dissipation and mass accretion rates across disk radii show coherence for frequencies below the local viscous frequency. This is consistent with the coherence behavior observed in astrophysical sources such as Cygnus X-1.},

doi = {10.1088/0004-637X/791/2/126},

journal = {Astrophysical Journal},

number = 2,

volume = 791,

place = {United States},

year = {Wed Aug 20 00:00:00 EDT 2014},

month = {Wed Aug 20 00:00:00 EDT 2014}

}