Cross-scale interactions between turbulence driven by electron and ion temperature gradients via sub-ion-scale structures

Maeyama, Shinya; Watanabe, T.‐H.; Idomura, Yasuhiro; Nakata, M.; Ishizawa, A.; Nunami, M.

doi:10.1088/1741-4326/aa687c

Cited by 20 publications

(42 citation statements)

References 25 publications

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“…Here, k θ is the poloidal wavenumber, ρ e is the electron gyroradius, and ρ s is the ion gyroradius evaluated with the ion sound speed (c s = T e /m i ). This indicates that multi-scale interactions and cross-scale energy transport recently discovered in nonlinear gyrokinetic simulations [23,26] play a subdominant role in determining the coldpulse dynamics in these experiments.…”

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confidence: 63%

Explaining Cold-Pulse Dynamics in Tokamak Plasmas Using Local Turbulent Transport Models

et al. 2018

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A long-standing enigma in plasma transport has been resolved by modeling of cold-pulse experiments conducted on the Alcator C-Mod tokamak. Controlled edge cooling of fusion plasmas triggers core electron heating on time scales faster than an energy confinement time, which has long been interpreted as strong evidence of nonlocal transport. This Letter shows that the steady-state profiles, the cold-pulse rise time, and disappearance at higher density as measured in these experiments are successfully captured by a recent local quasilinear turbulent transport model, demonstrating that the existence of nonlocal transport phenomena is not necessary for explaining the behavior and time scales of cold-pulse experiments in tokamak plasmas.

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confidence: 63%

Explaining Cold-Pulse Dynamics in Tokamak Plasmas Using Local Turbulent Transport Models

et al. 2018

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“…However, there remain many examples where this is not the case, with the simulations unable to match the ion heat flu, Q i [10,11] or the electron heat flux, Q e [12][13][14][15]. In the cases where ion scale simulations are unable to match the electron heat flux, it has been suggested that electron scale turbulence may be playing a role, either directly [16,17] or through non-linear multi-scale coupling of ion and electron turbulence [18][19][20]. Since this latter case requires simulations which are presently almost prohibitively computationally expensive, it is of a very high importance to identify the region of parameter space where single scale simulations suffice.…”

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confidence: 99%

Validation of gyrokinetic simulations with measurements of electron temperature fluctuations and density-temperature phase angles on ASDEX Upgrade

et al. 2018

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Measurements of turbulent electron temperature fluctuation amplitudes, δT e⊥ /Te, frequency spectra and radial correlation lengths, Lr(T e⊥ ), have been performed at ASDEX Upgrade using a newly upgraded Correlation ECE diagnostic in the range of scales k ⊥ < 1.4cm −1 , kr < 3.5cm(k ⊥ ρs < 0.28 and krρs < 0.7). The phase angle between turbulent temperature and density fluctuations, αnT , has also been measured by using an ECE radiometer coupled to a reflectometer along the same line of sight. These quantities are used simultaneously to constrain a set of ion-scale nonlinear gyrokinetic turbulence simulations of the outer core (ρtor = 0.75) of a low density, electron heated L-mode plasma, performed using the gyrokinetic simulation code, GENE. The ion and electron temperature gradients were scanned within uncertainties. It is found that GK simulations are able to match simultaneously the electron and ion heat flux at this radius within the experimental uncertainties. The simulations were performed based on a reference discharge for which δT e⊥ /Te measurements were available, and Lr(T e⊥ ) and αnT were then predicted using synthetic diagnostics prior to measurements in a repeat discharge. While temperature fluctuation amplitudes are overestimated by > 50% for all simulations within the sensitivity scans performed, good quantitative agreement is found for Lr(T e⊥ ) and αnT . A validation metric is used to quantify the level of agreement of individual simulations with experimental measurements, and the best agreement is found close to the experimental gradient values.

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“…To gauge this interplay, using only the net free energy received by a mode from the nonlinear interaction with all other modes, i.e. T (k x , k y , z), see previous works [35,36] or the equivalent definition in [37], we define the overall flux of free energy across the k ? (z) scales as ⇧(k ?…”

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confidence: 99%

Impact of electron-scale turbulence and multi-scale interactions in the JET tokamak

et al. 2018

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Experimental observations in JET tokamak plasmas and gyrokinetic simulations point to an important role, for electron heat transport, of electron-scale instabilities and of their interaction with ion-scale instabilities. Since these effects are maximized for strong electron heating and ion-scale modes close to marginal stability, these findings are of high relevance for ITER plasmas, featuring both conditions. Gyrokinetic and quasi-linear transport models accounting for multi-scale effects are assessed against JET experimental results.

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Cross-scale interactions between turbulence driven by electron and ion temperature gradients via sub-ion-scale structures

Cited by 20 publications

References 25 publications

Explaining Cold-Pulse Dynamics in Tokamak Plasmas Using Local Turbulent Transport Models

Explaining Cold-Pulse Dynamics in Tokamak Plasmas Using Local Turbulent Transport Models

Validation of gyrokinetic simulations with measurements of electron temperature fluctuations and density-temperature phase angles on ASDEX Upgrade

Impact of electron-scale turbulence and multi-scale interactions in the JET tokamak

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