The collisional drift wave instability in steep density gradient regimes

Held, Markus; Wiesenberger, Matthias; Kendl, A.

doi:10.1088/1741-4326/aaf6cc

Cited by 9 publications

(12 citation statements)

References 51 publications

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“…This E × B shear flow is believed to emerge out of turbulent fluctuations via the Reynolds stress, yet other mechanisms like the ion-orbit loss mechanism [12,13,14] or the Favre stress and background density gradient drive [15] are currently under discussion as well. Recent results suggest that the latter significantly alter the generation mechanism of E × B zonal flows for high density fluctuation amplitudes and steep density gradients [15,16].…”

Section: Introductionmentioning

confidence: 99%

Angular momentum and rotational energy of meanflows in toroidal magnetic fields

Wiesenberger¹,

Held²

2020

Preprint

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We derive the balance equation for the Favre averaged angular momentum in toroidal not necessarily axisymmetric magnetic field equilibria. These include tokamaks, stellarators, the reversed field pinch and field-reversed configurations. We find that the components of angular momentum are given by the covariant poloidal and toroidal components of E×B and parallel flow velocities and we separately identify all relevant stress tensors, torques and source terms for each of these components. Our results feature the Favre stress generalisations of previously found Reynolds stresses like the diamagnetic or parallel E × B stress. Further, we identify the magnetic shear as a source of poloidal E × B angular momentum and discuss the mirror and the Lorentz force. Here, we find that the geodesic transfer term, the Stringer-Winsor spin-up term and the ion-orbit loss term are all part of the Lorentz force and are in fact one and the same term.Discussing the relation to angular velocity we build the inertia tensor with the help of the first fundamental form of a flux-surface. In turn, the inertia tensor is used to construct a flux-surface averaged rotational energy for E × B surface flows of the plasma. The evolution of this rotational energy features a correction of previous results due to the inertia tensor. In particular, this correction suggests that density sources on the high-field side contribute much more to zonal flow energy generation than on the low field side.Our derivation is based on a full-F, electromagnetic, gyro-kinetic model in a long-wavelength limit. The results can be applied to gyro-kinetic as well as gyrofluid theories and can also be compared to drift-kinetic and drift-fluid models. Simplified cases for the magnetic field geometry including the axisymmetric purely toroidal and purely poloidal magnetic fields are discussed, as are the angular momentum balance of the electromagnetic fields, the ion-orbit loss mechanism and the parallel acceleration.

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Section: Introductionmentioning

confidence: 99%

Angular momentum and rotational energy of meanflows in toroidal magnetic fields

Wiesenberger¹,

Held²

2020

Preprint

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“…1. The relative error of the (1,2) and (1,4) Padé-approximation to Γ 0 are of comparable magnitude and are roughly 7% and respectively 11%. Additionally, the O b 10 and O b 18 accurate approximations are shown.…”

Section: B Polarization Closuresmentioning

confidence: 86%

“…( 22) respectively the N = 2 limit of Eq. ( 19)) the truncated polarization operator is simply the (1,2) or (1,4) Padé-approximation of the polarization operator, so that Γ 0,1 = 1 2 Γ 0 or Γ 0,2 = 1 4 Γ 0 . The latter Padéapproximations retain high accuracy to the Maxwellian polarization operator Γ 0 , which is depicted in Fig.…”

Section: B Polarization Closuresmentioning

confidence: 99%

“…Gyro-fluid (GF) models are an extremely useful approach to provide insights into the behavior of magnetized plasmas. They are widely applied to study turbulent transport in the tokamak core [1,2], edge [3,4] and scrape-off layer [5][6][7][8][9] and phenomena like collisionless reconnection [10], zonal flows [11,12] and edge localized modes [13,14]. GF models origin from gyro-kinetic theory [15][16][17] and rely on precise fluid closures to incorporate kinetic effects.…”

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confidence: 99%

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Padé-based arbitrary wavelength polarization closures for full-F gyro-kinetic and -fluid models

Held,

Wiesenberger,

Kendl

2019

Preprint

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We propose a solution to the long-standing long wavelength polarization closure shortfall of full-F gyro-fluid models. This is achieved by first finding an appropriate quadratic form of the gyro-fluid moment over the second order Hamiltonian. Secondly, we deduce Padé-based approximations to the latter expression, that produce a polarization charge density with the opted order of accuracy and mimic linear polarization effects for arbitrary wavelengths. The proposed closures feature proper energy conservation and the anticipated Oberbeck-Boussinesq and long wavelength limit.

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“…Subsequently, also drift wave-interchange turbulence, zonal flow and vortex dynamics were addressed with this full-F gyro-fluid model (Held 2017; Held et al. 2018; Held, Wiesenberger & Kendl 2019). From these studies it has emerged that in the assumed long-wavelength (‘low-k’) approximation of Strintzi & Scott (2004, 2005) and Madsen (2013), is, however, missing a physically relevant FLR effect in the polarisation density that appears in the quasi-neutrality constraint (Held, Wiesenberger & Kendl 2020).…”

Section: Full-f Multi-species Gyro-fluid Model Of Interchange Blob Tr...mentioning

confidence: 99%

Non-trace full-F gyro-fluid interchange impurity advection

et al. 2023

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A full-F isothermal gyro-fluid model and code (which is based on the full distribution function F compared to only small fluctuations) is extended to handle self-consistent coupling of multiple quasi-neutral ion species via the polarisation equation in the long wavelength approximation. The numerical model is used to determine two-dimensional interchange driven ‘blob’ transport in a plasma with intrinsic impurity content for a range of impurity parameters. With the same model, the self-consistent advective interaction of a main plasma species blob with a non-trace impurity cloud is studied. For homogeneous impurity distributions an increased effective mass reduces blob transport, whereas it is found that localised impurity clouds can lead either to acceleration or slowing down of blob propagation depending on the alignment of the impurity density gradient during the acceleration phase of the main ion species blob.

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The collisional drift wave instability in steep density gradient regimes

Cited by 9 publications

References 51 publications

Angular momentum and rotational energy of meanflows in toroidal magnetic fields

Angular momentum and rotational energy of meanflows in toroidal magnetic fields

Padé-based arbitrary wavelength polarization closures for full-F gyro-kinetic and -fluid models

Non-trace full-F gyro-fluid interchange impurity advection

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