Effects of parallel ion motion on electromagnetic toroidal ion temperature gradient modes in a fluid model

Jarmén, A.; Anderson, Johan; Malinov, P. N.

doi:10.1063/1.4928374

Cited by 1 publication

(1 citation statement)

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“…This efficiently transfers energy out of the ITG mode, reducing its growth. Alterations of the ion Landau resonance due to finite-equilibrium- modifications from the bending of perturbed field lines can also play a role in the stabilization (Jarmén, Anderson & Malinov 2015). This reduction in growth rate will tend to reduce the nonlinear heat flux, but additional physics can also have an impact on the dynamics.…”

Section: Electromagnetic Itg and Kbm Turbulencementioning

confidence: 99%

Kinetic-ballooning-mode turbulence in low-average-magnetic-shear equilibria

et al. 2021

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Kinetic-ballooning-mode (KBM) turbulence is studied via gyrokinetic flux-tube simulations in three magnetic equilibria that exhibit small average magnetic shear: the Helically Symmetric eXperiment (HSX), the helical-axis Heliotron-J and a circular tokamak geometry. For HSX, the onset of KBM being the dominant instability at low wavenumber occurs at a critical value of normalized plasma pressure $\beta ^{\rm KBM}_{\rm crit}$ that is an order of magnitude smaller than the magnetohydrodynamic (MHD) ballooning limit $\beta ^{\rm MHD}_{\rm crit}$ when a strong ion temperature gradient (ITG) is present. However, $\beta ^{\rm KBM}_{\rm crit}$ increases and approaches the MHD ballooning limit as the ITG tends to zero. For these configurations, $\beta ^{\rm KBM}_{\rm crit}$ also increases as the magnitude of the average magnetic shear increases, regardless of the sign of the normalized magnetic shear. Simulations of Heliotron-J and a circular axisymmetric geometry display behaviour similar to HSX with respect to $\beta ^{\rm KBM}_{\rm crit}$ . Despite large KBM growth rates at long wavelengths in HSX, saturation of KBM turbulence with $\beta > \beta _{\rm crit}^{\rm KBM}$ is achievable in HSX and results in lower heat transport relative to the electrostatic limit by a factor of roughly five. Nonlinear simulations also show that KBM transport dominates the dynamics when KBMs are destabilized linearly, even if KBM growth rates are subdominant to ITG growth rates.

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Section: Electromagnetic Itg and Kbm Turbulencementioning

confidence: 99%