# ANALYSIS OF MAGNETOROTATIONAL INSTABILITY WITH THE EFFECT OF COSMIC-RAY DIFFUSION

## Abstract

We present the results obtained from the linear stability analysis and 2.5 dimensional magnetohydrodynamic (MHD) simulations of magnetorotational instability (MRI), including the effects of cosmic rays (CRs). We took into account the CR diffusion along the magnetic field but neglected the cross-field-line diffusion. Two models are considered in this paper: the shearing box model and differentially rotating cylinder model. We studied how MRI is affected by the initial CR pressure (i.e., energy) distribution. In the shearing box model, the initial state is uniform distribution. Linear analysis shows that the growth rate of MRI does not depend on the value of the CR diffusion coefficient. In the differentially rotating cylinder model, the initial state is a constant angular momentum polytropic disk threaded by a weak uniform vertical magnetic field. Linear analysis shows that the growth rate of MRI becomes larger if the CR diffusion coefficient is larger. Both results are confirmed by MHD simulations. The MHD simulation results show that the outward movement of matter by the growth of MRI is not impeded by the CR pressure gradient, and the centrifugal force that acts on the concentrated matter becomes larger. Consequently, the growth rate of MRI is increased. On the othermore »

- Authors:

- Computational Science and Engineering Division I, AdvanceSoft Corporation, 4-3, Kanda Surugadai, Chiyoda-ku, Tokyo 101-0062 (Japan)
- Department of Physics, Institute of Astronomy and Center for Complex Systems, National Central University, Jhongli, Taiwan 320 (China)

- Publication Date:

- OSTI Identifier:
- 22364675

- Resource Type:
- Journal Article

- Resource Relation:
- Journal Name: Astrophysical Journal; Journal Volume: 798; 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; BOX MODELS; COMPUTERIZED SIMULATION; COSMIC RADIATION; DIFFUSION; ENERGY SPECTRA; GALAXIES; MAGNETIC FIELDS; MAGNETOHYDRODYNAMICS; PRESSURE GRADIENTS; SHEAR

### Citation Formats

```
Kuwabara, Takuhito, and Ko, Chung-Ming, E-mail: kuwabrtk@gmail.com, E-mail: cmko@astro.ncu.edu.tw.
```*ANALYSIS OF MAGNETOROTATIONAL INSTABILITY WITH THE EFFECT OF COSMIC-RAY DIFFUSION*. United States: N. p., 2015.
Web. doi:10.1088/0004-637X/798/2/79.

```
Kuwabara, Takuhito, & Ko, Chung-Ming, E-mail: kuwabrtk@gmail.com, E-mail: cmko@astro.ncu.edu.tw.
```*ANALYSIS OF MAGNETOROTATIONAL INSTABILITY WITH THE EFFECT OF COSMIC-RAY DIFFUSION*. United States. doi:10.1088/0004-637X/798/2/79.

```
Kuwabara, Takuhito, and Ko, Chung-Ming, E-mail: kuwabrtk@gmail.com, E-mail: cmko@astro.ncu.edu.tw. Sat .
"ANALYSIS OF MAGNETOROTATIONAL INSTABILITY WITH THE EFFECT OF COSMIC-RAY DIFFUSION". United States.
doi:10.1088/0004-637X/798/2/79.
```

```
@article{osti_22364675,
```

title = {ANALYSIS OF MAGNETOROTATIONAL INSTABILITY WITH THE EFFECT OF COSMIC-RAY DIFFUSION},

author = {Kuwabara, Takuhito and Ko, Chung-Ming, E-mail: kuwabrtk@gmail.com, E-mail: cmko@astro.ncu.edu.tw},

abstractNote = {We present the results obtained from the linear stability analysis and 2.5 dimensional magnetohydrodynamic (MHD) simulations of magnetorotational instability (MRI), including the effects of cosmic rays (CRs). We took into account the CR diffusion along the magnetic field but neglected the cross-field-line diffusion. Two models are considered in this paper: the shearing box model and differentially rotating cylinder model. We studied how MRI is affected by the initial CR pressure (i.e., energy) distribution. In the shearing box model, the initial state is uniform distribution. Linear analysis shows that the growth rate of MRI does not depend on the value of the CR diffusion coefficient. In the differentially rotating cylinder model, the initial state is a constant angular momentum polytropic disk threaded by a weak uniform vertical magnetic field. Linear analysis shows that the growth rate of MRI becomes larger if the CR diffusion coefficient is larger. Both results are confirmed by MHD simulations. The MHD simulation results show that the outward movement of matter by the growth of MRI is not impeded by the CR pressure gradient, and the centrifugal force that acts on the concentrated matter becomes larger. Consequently, the growth rate of MRI is increased. On the other hand, if the initial CR pressure is uniform, then the growth rate of the MRI barely depends on the value of the CR diffusion coefficient.},

doi = {10.1088/0004-637X/798/2/79},

journal = {Astrophysical Journal},

number = 2,

volume = 798,

place = {United States},

year = {Sat Jan 10 00:00:00 EST 2015},

month = {Sat Jan 10 00:00:00 EST 2015}

}