The effect of weak collisionality on damped modes and its contribution to linear mode coupling in gyrokinetic simulation

Journal Article · Thu Aug 15 04:00:00 EDT 2013 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.4819033· OSTI ID:22227881

Hilscher, P. P.; Imadera, K.; Li, J. Q. ^[1]; Kishimoto, Y. ^[1]

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1. Graduate School of Energy Science, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan)

We revisit the characteristics of stable, damped modes originating from the Landau damping by employing a discretized gyrokinetic Vlasov simulation and also eigenvalue analysis in an unsheared slab geometry. By comparing results between gyrokinetic simulation and an eigenvalue analysis, we found that there exists a critical collisionality β{sub c}{sup *} at which the Case-van Kampen (CvK) modes are damped down to the analytically estimated Landau damping rate and an eigenmode consistent with Landau's theory emerges. Consequently, the recurrence phenomenon disappears so that the Landau damping can be properly reproduced. The critical collisionality β{sub c}{sup *} depends on the resolution in velocity space; i.e., a higher (lower) resolution requires a lower (higher) collisionality, while tends to zero (β{sub c}{sup *}→0) as Δv→0. It is found through a reduced model that even in the collisionless case with marginally stable CvK modes, the linear mode coupling between unstable and stable/damped components through a tertiary mode and the resultant energy transfer can be properly calculated such that the stable/damped mode persists as an eigenstate.

• OSTI ID: 22227881
• Journal Information: Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 8 Vol. 20; ISSN PHPAEN; ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
BOLTZMANN-VLASOV EQUATION
COLLISIONLESS PLASMA
COMPARATIVE EVALUATIONS
EIGENFUNCTIONS
EIGENVALUES
ENERGY TRANSFER
LANDAU DAMPING
PLASMA INSTABILITY
PLASMA SIMULATION
TURBULENCE