Eigenmode analysis of geodesic acoustic modes

Journal Article · Tue Jul 15 04:00:00 EDT 2008 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.2956993· OSTI ID:21268967

Zhe, Gao ^[1]; Itoh, K; Sanuki, H ^[2]; Dong, J Q ^[3]

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1. Department of Engineering Physics, Tsinghua University, Beijing 100084 (China)
2. National Institute for Fusion Science, Toki, Gifu 509-5292 (Japan)
3. Southwestern Institute of Physics, Chengdu 610041 (China)

Geodesic acoustic modes (GAMs) are studied as plasma eigenmodes when an electrostatic potential nearly constant around a magnetic surface is applied to collisionless toroidal plasmas. Besides the standard GAM, a branch of low frequency mode and an infinite series of ion sound wavelike modes are identified. Eigenfrequencies of these modes are obtained analytically and numerically from a linear gyrokinetic model. The finite gyroradius effect is found to enhance the collisionless damping of the standard GAM, while this enhancement is not monotonic as the safety factor varies. Moreover, additional damping due to higher-harmonic resonances becomes important when the safety factor increases. The mode structure of the GAM is also discussed.

• OSTI ID: 21268967
• Journal Information: Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 7 Vol. 15; ISSN PHPAEN; ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
ANALYTICAL SOLUTION
COLLISIONLESS PLASMA
EIGENFREQUENCY
ION ACOUSTIC WAVES
MAGNETIC SURFACES
NUMERICAL SOLUTION