The effect of weak collisionality on damped modes and its contribution to linear mode coupling in gyrokinetic simulation
The effect of weak collisionality on damped modes and its contribution to linear mode coupling in gyrokinetic simulation
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DOI：
10.1063/1.4819033
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发表时间：
2013-08
影响因子：
2.2
通讯作者：
Paul P. Hilscher;K. Imadera;Jiquan Li;Y. Kishimoto
中科院分区：
文献类型：
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作者：
Paul P. Hilscher;K. Imadera;Jiquan Li;Y. Kishimoto
我们通过采用离散的陀螺动力学Vlasov模拟和非剪切板几何的特征值分析，重新审视了源自朗道阻尼的稳定阻尼模态的特征。通过对陀螺动力学模拟和特征值分析结果的比较，我们发现存在一个临界碰撞βc - -，在这个碰撞βc - -下，Case-van Kampen （CvK）模态被衰减到解析估计的朗道阻尼率，并出现一个符合朗道理论的特征模态。因此，递归现象消失，从而可以适当地再现朗道阻尼。临界碰撞βc -取决于速度空间的分辨率；即，更高（更低）的分辨率需要更低（更高）的碰撞，而趋于零（βc -→0）为Δv→0。通过简化模型发现，即使在具有边际稳定CvK模态的无碰撞情况下，不稳定和稳定/阻尼分量之间的线性模态耦合也通过三阶模态，结果表明：
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 βc⋆ 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 βc⋆ depends on the resolution in velocity space; i.e., a higher (lower) resolution requires a lower (higher) collisionality, while tends to zero (βc⋆→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 resul...