Effect of Drift Waves on Plasma Blob Dynamics

Angus, J. R.; Umansky, M.; Krasheninnikov, S. I.

doi:10.1103/physrevlett.108.215002

Cited by 55 publications

(78 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…al [30,31]. The system defined by equations (12), (13) and (4) supports the linear interchange instability and the linear resistive drift wave instability [30,31]. The interchange instability is destabilized by perpendicular gradients in pressure, or (since the model is isothermal) density gradients, such as those at the blob front.…”

Section: Governing Equationsmentioning

confidence: 99%

“…This is the system employed in the 3D studies by Angus et. al [30,31]. The system defined by equations (12), (13) and (4) supports the linear interchange instability and the linear resistive drift wave instability [30,31].…”

Section: Governing Equationsmentioning

confidence: 99%

“…Recently accounting for the full 3D nature of filaments has been shown to lead to a significant departure of the blob dynamics from 2D theory [30,31,20]. When the linear growth rate of the resistive drift-wave instability is larger than the interchange growth rate on the blob front (with respect to propagation direction) the blob becomes unstable to resistive drift waves [30]. The blob becomes much more diffuse and less coherent than its 2D counterpart.…”

Section: Introductionmentioning

confidence: 99%

“…In the former case the filament exhibits the mushrooming characteristic, with smaller scale structure appearing depending on the viscosity and resistivity of the plasma [16] due to Kelvin-Helmholtz instabilities. Recently accounting for the full 3D nature of filaments has been shown to lead to a significant departure of the blob dynamics from 2D theory [30,31,20]. When the linear growth rate of the resistive drift-wave instability is larger than the interchange growth rate on the blob front (with respect to propagation direction) the blob becomes unstable to resistive drift waves [30].…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Characterization of 3D filament dynamics in a MAST SOL flux tube geometry

Walkden

Dudson

Fishpool

2013

Plasma Phys. Control. Fusion

View full text Add to dashboard Cite

Abstract. Non-linear simulations of filament propagation in a realistic MAST SOL flux tube geometry using the BOUT++ fluid modelling framework show an isolation of the dynamics of the filament in the divertor region from the midplane region due to three features of the magnetic geometry; the variation of magnetic curvature along the field line, the expansion of the flux tube and strong magnetic shear. Of the three effects, the latter two lead to a midplane ballooning feature of the filament, whilst the former leads to a ballooning around the X-points. In simulations containing all three effects the filament is observed to balloon at the midplane, suggesting that the role of curvature variation is sub-dominant to the flux expansion and magnetic shear. The magnitudes of these effects are all strongest near the X-point which leads to the formation of parallel density gradients. The filaments simulated, which represent filaments in MAST, are identified as resistive ballooning, meaning that their motion is inertially limited, not sheath limited. Parallel density gradients can drive the filament towards a Boltzmann response when the collisionalityof the plasma is low. The results here show that the formation of parallel density gradients is a natural and inevitable consequence of a realistic magnetic geometry and therefore the transition to the Boltzmann response is a consequence of the use of realistic magnetic geometry and does not require initializing specifically varying background profiles as in slab simulations. The filaments studied here are stable to the linear resistive drift wave instability but are subject to the non-linear effects associated with the Boltzmann response, particularly Boltzmann spinning. The Boltzmann response causes the filament to self-organise and spin on an axis. In later stages of its evolution a non-linear turbulent state develops where the vorticity evolves into a turbulent eddy field on the same length scale as the parallel current. The transition from interchange motion to the Boltzmann response occurs with increasing temperature through a decrease in collisionality. This is confirmed by measuring the correlation between density and potential perturbations within the filament, which is low in the anti-symmetric state associated with the interchange mechanism, but high in the Boltzmann regime. In the Boltzmann regime net radial transport is drastically reduced whilst a small net toroidal transport is observed. This suggests that only a subset of filaments, those driven by the interchange mechanism at the separatrix, can propagate into the far SOL. Filaments in the Boltzmann regime will be confined to the near separatrix region and quickly disperse. It is plausible that filaments in both regimes can contribute to the SOL transport observed in experiment; the former by propagating the filament into the far SOL and the latter by dispersion of the density within the filament.

show abstract

Section: Governing Equationsmentioning

confidence: 99%

Section: Governing Equationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Characterization of 3D filament dynamics in a MAST SOL flux tube geometry

Walkden

Dudson

Fishpool

2013

Plasma Phys. Control. Fusion

View full text Add to dashboard Cite

show abstract

“…In sum, most of the effects which are believed to play an important role for the plasma blob dynamics are included at least in the near SOL, namely, three- dimensional [36], electromagnetic [37], finite ion temperature or finite Larmor radius [38][39][40] and shear flow (amongst others the zonal flow and the geodesic acoustic mode) effects [7,8,11]. More details on the present simulation parameters can be found in Ref.…”

Section: Gemr Simulationmentioning

confidence: 99%

Turbulent transport across shear layers in magnetically confined plasmas

et al. 2014

View full text Add to dashboard Cite

Shear layers modify the turbulence in diverse ways and do not only suppress it. A spatialtemporal investigation of gyrofluid simulations in comparison with experiments allows to identify further details of the transport process across shear layers. Blobs in and outside a shear layer merge, thereby exchange particles and heat and subsequently break up. Via this mechanism particles and heat are transported radially across shear layers. Turbulence spreading is the immanent mechanism behind this process.

show abstract