# Energetic-particle-induced electromagnetic geodesic acoustic mode in tokamak plasmas

## Abstract

Energetic-particle-induced kinetic electromagnetic geodesic acoustic modes (EKEGAMs) are numerically studied in low β (=plasma pressure/magnetic pressure) tokamak plasmas. The parallel component of the perturbed vector potential is considered along with the electrostatic potential perturbation. The effects of finite Larmor radius and finite orbit width of the bulk and energetic ions as well as electron parallel dynamics are all taken into account in the dispersion relation. Systematic harmonic and ordering analysis are performed for frequency and growth rate spectra of the EKEGAMs, assuming (kρ{sub i})∼q{sup −3}∼β≪1, where q, k, and ρ{sub i} are the safety factor, radial component of the EKEGAMs wave vector, and the Larmor radius of the ions, respectively. It is found that there exist critical β{sub h}/β{sub i} values, which depend, in particular, on pitch angle of energetic ions and safety factor, for the mode to be driven unstable. The EKEGAMs may also be unstable for pitch angle λ{sub 0}B<0.4 in certain parameter regions. Finite β effect of the bulk ions is shown to have damping effect on the EKEGAMs. Modes with higher radial wave vectors have higher growth rates. The damping from electron dynamics is found decreasing with decrease of the temperature ratio T{sub e}/T{sub i}. Themore »

- Authors:

- Southwestern Institute of Physics, Chengdu 610041 (China)
- Institute for Fusion Theory and Simulation, Zhejiang University, Hangzhou 310027 (China)
- (China)

- Publication Date:

- OSTI Identifier:
- 22299829

- Resource Type:
- Journal Article

- Resource Relation:
- Journal Name: Physics of Plasmas; Journal Volume: 21; Journal Issue: 7; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; DAMPING; DISPERSION RELATIONS; ELECTRONS; INCLINATION; LARMOR RADIUS; PERTURBATION THEORY; PLASMA PRESSURE; TAIL IONS; TOKAMAK DEVICES; VECTORS

### Citation Formats

```
Wang, Lingfeng, E-mail: wanglf@swip.ac.cn, He, Zhixiong, He, Hongda, Shen, Y., Dong, J. Q., and Southwestern Institute of Physics, Chengdu 610041.
```*Energetic-particle-induced electromagnetic geodesic acoustic mode in tokamak plasmas*. United States: N. p., 2014.
Web. doi:10.1063/1.4890467.

```
Wang, Lingfeng, E-mail: wanglf@swip.ac.cn, He, Zhixiong, He, Hongda, Shen, Y., Dong, J. Q., & Southwestern Institute of Physics, Chengdu 610041.
```*Energetic-particle-induced electromagnetic geodesic acoustic mode in tokamak plasmas*. United States. doi:10.1063/1.4890467.

```
Wang, Lingfeng, E-mail: wanglf@swip.ac.cn, He, Zhixiong, He, Hongda, Shen, Y., Dong, J. Q., and Southwestern Institute of Physics, Chengdu 610041. Tue .
"Energetic-particle-induced electromagnetic geodesic acoustic mode in tokamak plasmas". United States.
doi:10.1063/1.4890467.
```

```
@article{osti_22299829,
```

title = {Energetic-particle-induced electromagnetic geodesic acoustic mode in tokamak plasmas},

author = {Wang, Lingfeng, E-mail: wanglf@swip.ac.cn and He, Zhixiong and He, Hongda and Shen, Y. and Dong, J. Q. and Southwestern Institute of Physics, Chengdu 610041},

abstractNote = {Energetic-particle-induced kinetic electromagnetic geodesic acoustic modes (EKEGAMs) are numerically studied in low β (=plasma pressure/magnetic pressure) tokamak plasmas. The parallel component of the perturbed vector potential is considered along with the electrostatic potential perturbation. The effects of finite Larmor radius and finite orbit width of the bulk and energetic ions as well as electron parallel dynamics are all taken into account in the dispersion relation. Systematic harmonic and ordering analysis are performed for frequency and growth rate spectra of the EKEGAMs, assuming (kρ{sub i})∼q{sup −3}∼β≪1, where q, k, and ρ{sub i} are the safety factor, radial component of the EKEGAMs wave vector, and the Larmor radius of the ions, respectively. It is found that there exist critical β{sub h}/β{sub i} values, which depend, in particular, on pitch angle of energetic ions and safety factor, for the mode to be driven unstable. The EKEGAMs may also be unstable for pitch angle λ{sub 0}B<0.4 in certain parameter regions. Finite β effect of the bulk ions is shown to have damping effect on the EKEGAMs. Modes with higher radial wave vectors have higher growth rates. The damping from electron dynamics is found decreasing with decrease of the temperature ratio T{sub e}/T{sub i}. The modes are easily to be driven unstable in low safety factor q region and high temperature ratio T{sub h}/T{sub i} region. The harmonic features of the EKEGAMs are discussed as well.},

doi = {10.1063/1.4890467},

journal = {Physics of Plasmas},

number = 7,

volume = 21,

place = {United States},

year = {Tue Jul 15 00:00:00 EDT 2014},

month = {Tue Jul 15 00:00:00 EDT 2014}

}