ORCID Profile
0000-0003-3273-2604
Current Organisations
Kyushu University
,
Peking University
,
Springer Nature (Switzerland)
,
University of California, San Diego
,
Southwestern Institute of Physics
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Publications
Turbulent diffusion of magnetic fields in two-dimensional magnetohydrodynamic turbulence with stable stratification
Publisher: American Physical Society (APS)
Date: 29-11-2007
An overview of intrinsic torque and momentum transport bifurcations in toroidal plasmas
Publisher: IOP Publishing
Date: 26-09-2013
Experimental progress on zonal flow physics in toroidal plasmas
Publisher: IOP Publishing
Date: 19-09-2007
Turbulent resistivity in wavy two-dimensional magnetohydrodynamic turbulence
Publisher: Cambridge University Press (CUP)
Date: 08-01-2008
DOI: 10.1017/S002211200700941X
Abstract: The theory of turbulent resistivity in ‘wavy’ magnetohydrodynamic turbulence in two dimensions is presented. The goal is to explore the theory of quenching of turbulent resistivity in a regime for which the mean field theory can be rigorously constructed at large magnetic Reynolds number Rm . This is achieved by extending the simple two-dimensional problem to include body forces, such as buoyancy or the Coriolis force, which convert large-scale eddies into weakly interacting dispersive waves. The turbulence-driven spatial flux of magnetic potential is calculated to fourth order in wave slope – the same order to which one usually works in wave kinetics. However, spatial transport, rather than spectral transfer, is the object here. Remarkably, adding an additional restoring force to the already tightly constrained system of high Rm magnetohydrodynamic turbulence in two dimensions can actually increase the turbulent resistivity, by admitting a spatial flux of magnetic potential which is not quenched at large Rm , although it is restricted by the conditions of applicability of weak turbulence theory. The absence of Rm -dependent quenching in this wave-interaction-driven flux is a consequence of the presence of irreversibility due to resonant nonlinear three-wave interactions, which are independent of collisional resistivity. The broader implications of this result for the theory of mean field electrodynamics are discussed.
Particle transport in low-collisionality H-mode plasmas on DIII-D
Publisher: IOP Publishing
Date: 09-2015
On cross-phase and the quenching of the turbulent diffusion of magnetic fields in two dimensions
Publisher: American Astronomical Society
Date: 11-04-2008
DOI: 10.1086/588654
Physics of intrinsic rotation in flux-driven ITG turbulence
Publisher: IOP Publishing
Date: 27-04-2012
DOI: 10.1088/0029-5515/52/6/063013
Abstract: Global, heat flux-driven ITG gyrokinetic simulations which manifest the formation of macroscopic, mean toroidal flow profiles with peak thermal Mach number 0.05, are reported. Both a particle-in-cell (XGC1p) and a semi-Lagrangian (G YSELA ) approach are utilized without a priori assumptions of scale separation between turbulence and mean fields. Flux-driven ITG simulations with different edge flow boundary conditions show in both approaches the development of net unidirectional intrinsic rotation in the co-current direction. Intrinsic torque is shown to scale approximately linearly with the inverse scale length of the ion temperature gradient. External momentum input is shown to effectively cancel the intrinsic rotation profile, thus confirming the existence of a local residual stress and intrinsic torque. Fluctuation intensity, intrinsic torque and mean flow are demonstrated to develop inwards from the boundary. The measured correlations between residual stress and two fluctuation spectrum symmetry breakers, namely E × B shear and intensity gradient, are similar. Avalanches of (positive) heat flux, which propagate either outwards or inwards, are correlated with avalanches of (negative) parallel momentum flux, so that outward transport of heat and inward transport of parallel momentum are correlated and mediated by avalanches. The probability distribution functions of the outward heat flux and the inward momentum flux show strong structural similarity.
The role of zonal flows and predator–prey oscillations in triggering the formation of edge and core transport barriers
Publisher: IOP Publishing
Date: 24-04-2014
Mechanisms for generating toroidal rotation in tokamaks without external momentum input
Publisher: AIP Publishing
Date: 30-03-2010
DOI: 10.1063/1.3328521
Abstract: Recent experiments on DIII-D [J. L. Luxon, Nucl. Fusion 42, 614 (2002)] and National Spherical Torus Experiment (NSTX) [M. Ono et al., Nucl. Fusion 40, 557 (2000)] have focused on investigating mechanisms of driving rotation in fusion plasmas. The so-called intrinsic rotation is generated by an effective torque, driven by residual stresses in the plasma, which appears to originate in the plasma edge. A clear scaling of this intrinsic drive with the H-mode pressure gradient is observed. Coupled with the experimentally inferred pinch of angular momentum, such an edge source is capable of producing sheared rotation profiles. Intrinsic drive is also possible directly in the core, although the physics mechanisms are much more complex. Another option which is being explored is the use of nonresonant magnetic fields for spinning the plasma. It is found beneficially that the torque from these fields can be enhanced at low rotation, which assists in spinning the plasma from rest, and offers increased resistance against plasma slowing.
Related Organisations
Massachusetts Institute Of Technology
Location: United States of America
University Of California, San Diego
Location: United States of America
Massacheusetts Institute Of Technology
Location: United States of America
Related Funding Activities
No related grants have been discovered for Patrick H. Diamond.