A reduced MHD model for ITG-NTM interplay

Frank, J.; Agullo, O.; Maget, P.; Garbet, X.; Dubuit, N.; Muraglia, M.

doi:10.1063/1.5141933

Cited by 3 publications

(4 citation statements)

References 57 publications

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“…The present study is performed using a six-field fluid model developed starting from the usual Braginskii fluid equations (Braginskii 1965), retaining, as detailed in Frank et al. (2020), neoclassical effects in the Pfirsch–Schlüter regime and the dynamics of trace impurities. These two latter points will not be considered in the present study, but are a possible future application of the model.…”

Section: A Six-field Fluid Modelmentioning

confidence: 99%

“…A difference with respect to the model described in Frank et al. (2020) is that all terms of this kind are kept in all the equations, not only in the pressure equations. Also kept are the compression of (but not the advection by) the polarization velocity in the equation for the ion pressure and for the perpendicular dynamics (more on this in Appendix A), and the advection by the parallel velocity for both ions and electrons.…”

Section: A Six-field Fluid Modelmentioning

confidence: 99%

“…It must be emphasized that the word 'cubic' does not refer to the order at which a series expansion is stopped, but to the fact that, directly from the derivation of the transport equations, the model presents terms that combine three fields at once. A difference with respect to the model described in Frank et al (2020) is that all terms of this kind are kept in all the equations, not only in the pressure equations. Also kept are the compression of (but not the advection by) the polarization velocity in the equation for the ion pressure and for the perpendicular dynamics (more on this in Appendix A), and the advection by the parallel velocity for both ions and electrons.…”

Section: A Six-field Fluid Modelmentioning

confidence: 99%

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Localized compressional self-heating in magnetic islands

et al. 2022

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A spontaneous heating process is found to arise in a system where a magnetic island is present due to a linearly unstable tearing mode. The parity, the relative phases and the structure of the fields determined linearly by the tearing mode cause the compression of the plasma in the direction parallel to the magnetic field to heat the plasma in the vicinity of the separatrix in the nonlinear phase. Using a six-field electromagnetic fluid model, the process is found to be present in both two-dimensional single-helicity and three-dimensional multi-helicity simulations with both symmetric and asymmetric magnetic equilibrium profiles. A noteworthy feature of the model is that the higher-order compression terms responsible for the heating process are retained in the equations. The process is believed to be linked to experimental observations of localized hot-spots on externally induced magnetic islands.

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Section: A Six-field Fluid Modelmentioning

confidence: 99%

Section: A Six-field Fluid Modelmentioning

confidence: 99%

Section: A Six-field Fluid Modelmentioning

confidence: 99%

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Localized compressional self-heating in magnetic islands

et al. 2022

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“…This term is required to initiate the pressure flattening inside the seed island when its size becomes larger than [6]. Of course a more complete description of neoclassical effects could be done following [37] leading to a 6-fields model but is out of the scope of this work. We aim to evaluate generalized Rutherford models by performing systematic comparisons between simulations and models.…”

Section: D-rmhd Model and Numerical Set-upmentioning

confidence: 99%

Nonlinear dynamics of NTM seeding by turbulence

Muraglia¹,

Poyé²,

Agullo³

et al. 2021

Plasma Phys. Control. Fusion

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In fusion devices, the prediction of large magnetic island dynamics and saturation is of utmost importance for disruption control strategies. In experiments, this prediction can be provided by generalized Rutherford models. The purpose of this paper is to present an unified comparison between Rutherford models and first-principles simulations, across the various mechanisms leading to the growth of a magnetic island. More precisely, systematic comparisons of generalized Rutherford models with numerical 2D-reduced-magneto-hydrodynamic simulations have been done for a simple tearing mode and for neoclassical tearing mode (NTM) in presence or not of turbulence in order to assess the suitability of using generalized Rutherford models in experiments. It is found that agreement between simulation and model is not straightforward. For a simple tearing mode, prediction of saturated island size is possible only if the island is small enough. However, generalized Rutherford models fail to predict the whole island dynamics and as a consequence the saturation time. Predicting the behavior of NTMs is possible by using fitting parameters in generalized Rutherford models. Moreover, although the seeding mechanism is not taken into account in generalized Rutherford models, simulations show that NTM dynamics and saturation depend on the physical mechanisms at play to seed the island. In particular, a NTM presents different dynamics whether or not turbulence is present. Finally, it is shown that the amplification of a turbulence driven magnetic island to a NTM requires a bootstrap current that is strong enough.

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Dynamics of magnetic islands driven by ballooning turbulence

et al. 2021

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Magnetic island generation by remote ballooning turbulence close to the plasma edge is investigated through ux-driven 3D Reduced-MHD simulations. The various coupling mechanisms are investigated : mono-helicity nonlinear coupling, multi-helicity nonlinear coupling and linear toroidal coupling. The dominant process depends on the imposed heat ux driving the turbulence. The remote drive happens in two successive phases corresponding to dierent coupling paths. While an island is remotely generated in both phases, it is dominated by dierent mode numbers, or harmonics, and therefore has a dierent shape. The size of the generated island is found to be proportional to the imposed heat ux, without threshold. The shape of the island in the saturated regime also depends on the imposed heat ux, with a more distorted shape at low power levels.

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A reduced MHD model for ITG-NTM interplay

Cited by 3 publications

References 57 publications

Localized compressional self-heating in magnetic islands

Localized compressional self-heating in magnetic islands

Nonlinear dynamics of NTM seeding by turbulence

Dynamics of magnetic islands driven by ballooning turbulence

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