Imperial College London

ProfessorStevenCowley

Faculty of Natural SciencesDepartment of Physics

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+44 (0)20 7594 7638steve.cowley Website

 
 
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735Blackett LaboratorySouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
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159 results found

Henneberg SA, Cowley SC, Wilson HR, 2018, Filamentary plasma eruptions: Results using the non-linear ballooning model, Contributions to Plasma Physics, Vol: 58, Pages: 6-20, ISSN: 0863-1042

© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim This paper provides an overview of recent results on two distinct studies exploiting the non-linear model for ideal ballooning modes with potential applications to edge-localized modes (ELMs). The non-linear model for tokamak geometries was developed by Wilson and Cowley in 2004 and consists of two differential equations that characterize the temporal and spatial evolution of the plasma displacement. The variation of the radial displacement along the magnetic field line is described by the first equation, which is identical to the linear ballooning equation. The second differential equation is a two-dimensional non-linear ballooning-like equation, which is often second order in time but can involve a fractional time derivative depending on the geometry. In the first study, the interaction of multiple filamentary eruptions is addressed in a magnetized plasma in a slab geometry. Equally sized filaments evolve independently in both the linear and non-linear regimes. However, if filaments are initiated with slightly different heights from the reference flux surface, they interact with each other in the non-linear regime: lower filaments are slowed down and are eventually completely suppressed, while the higher filaments grow faster because of the non-linear interaction. In the second study, this model of non-linear ballooning modes is examined quantitatively against experimental observations of ELMs in Mega Amp Spherical Tokamak (MAST) geometries. The results suggest that experimentally relevant results can only be obtained using modified equilibria.

JOURNAL ARTICLE

Cowley SC, 2016, The quest for fusion power, NATURE PHYSICS, Vol: 12, Pages: 384-386, ISSN: 1745-2473

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Ham CJ, Cowley SC, Brochard G, Wilson HRet al., 2016, Explosive Ballooning Flux Tubes in Tokamaks

Tokamak stability to, potentially explosive, `ballooning' displacements ofelliptical magnetic flux tubes is examined in large aspect ratio equilibrium.Above a critical pressure gradient the energy stored in the plasma may belowered by finite (but not infinitesimal) displacements of such tubes(metastability). Above a higher pressure gradient, the linear stabilityboundary, such tubes are linearly and nonlinearly unstable. The flux tubedisplacement can be of the order of the pressure gradient scale length. Plasmatransport from displaced flux tubes may result in rapid loss of confinement.

WORKING PAPER

Ham CJ, Cowley SC, Brochard G, Wilson HRet al., 2016, Nonlinear Stability and Saturation of Ballooning Modes in Tokamaks, PHYSICAL REVIEW LETTERS, Vol: 116, ISSN: 0031-9007

JOURNAL ARTICLE

Cowley SC, Cowley B, Henneberg SA, Wilson HRet al., 2015, Explosive instability and erupting flux tubes in a magnetized plasma, PROCEEDINGS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES, Vol: 471, ISSN: 1364-5021

JOURNAL ARTICLE

Henneberg SA, Cowley SC, Wilson HR, 2015, Interacting filamentary eruptions in magnetised plasmas, PLASMA PHYSICS AND CONTROLLED FUSION, Vol: 57, ISSN: 0741-3335

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Kunz MW, Schekochihin AA, Chen CHK, Abel IG, Cowley SCet al., 2015, Inertial-range kinetic turbulence in pressure-anisotropic astrophysical plasmas, JOURNAL OF PLASMA PHYSICS, Vol: 81, ISSN: 0022-3778

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Rincon F, Schekochihin AA, Cowley SC, 2015, Non-linear mirror instability, MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Vol: 447, Pages: L45-L49, ISSN: 0035-8711

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Cole MDJ, Newton SL, Cowley SC, Loureiro NF, Dickinson D, Roach C, Connor JWet al., 2014, Electromagnetic effects in the stabilization of turbulence by sheared flow, PLASMA PHYSICS AND CONTROLLED FUSION, Vol: 56, ISSN: 0741-3335

JOURNAL ARTICLE

Abel IG, Cowley SC, 2013, Multiscale gyrokinetics for rotating tokamak plasmas: II. Reduced models for electron dynamics, NEW JOURNAL OF PHYSICS, Vol: 15, ISSN: 1367-2630

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Abel IG, Plunk GG, Wang E, Barnes M, Cowley SC, Dorland W, Schekochihin AAet al., 2013, Multiscale gyrokinetics for rotating tokamak plasmas: fluctuations, transport and energy flows, REPORTS ON PROGRESS IN PHYSICS, Vol: 76, ISSN: 0034-4885

JOURNAL ARTICLE

Ghim Y-C, Schekochihin AA, Field AR, Abel IG, Barnes M, Colyer G, Cowley SC, Parra FI, Dunai D, Zoletnik Set al., 2013, Experimental Signatures of Critically Balanced Turbulence in MAST, PHYSICAL REVIEW LETTERS, Vol: 110, ISSN: 0031-9007

JOURNAL ARTICLE

Ham CJ, Connor JW, Cowley SC, Hastie RJ, Hender TC, Liu YQet al., 2013, The role of pressure flattening in calculating tearing mode stability, PLASMA PHYSICS AND CONTROLLED FUSION, Vol: 55, ISSN: 0741-3335

JOURNAL ARTICLE

Meyer H, Abel IG, Akers RJ, Allan A, Allan SY, Appel LC, Asunta O, Barnes M, Barratt NC, Ben Ayed N, Bradley JW, Canik J, Cahyna P, Cecconello M, Challis CD, Chapman IT, Ciric D, Colyer G, Conway NJ, Cox M, Crowley BJ, Cowley SC, Cunningham G, Danilov A, Darke A, De Bock MFM, De Temmerman G, Dendy RO, Denner P, Dickinson D, Dnestrovsky AY, Dnestrovsky Y, Driscoll MD, Dudson B, Dunai D, Dunstan M, Dura P, Elmore S, Field AR, Fishpool G, Freethy S, Fundamenski W, Garzotti L, Ghim YC, Gibson KJ, Gryaznevich MP, Harrison J, Havlickova E, Hawkes NC, Heidbrink WW, Hender TC, Highcock E, Higgins D, Hill P, Hnat B, Hole MJ, Horacek J, Howell DF, Imada K, Jones O, Kaveeva E, Keeling D, Kirk A, Kocan M, Lake RJ, Lehnen M, Leggate HJ, Liang Y, Lilley MK, Lisgo SW, Liu YQ, Lloyd B, Maddison GP, Mailloux J, Martin R, McArdle GJ, McClements KG, McMillan B, Michael C, Militello F, Molchanov P, Mordijck S, Morgan T, Morris AW, Muir DG, Nardon E, Naulin V, Naylor G, Nielsen AH, O'Brien MR, O'Gorman T, Pamela S, Parra FI, Patel A, Pinches SD, Price MN, Roach CM, Robinson JR, Romanelli M, Rozhansky V, Saarelma S, Sangaroon S, Saveliev A, Scannell R, Seidl J, Sharapov SE, Schekochihin AA, Shevchenko V, Shibaev S, Stork D, Storrs J, Sykes A, Tallents GJ, Tamain P, Taylor D, Temple D, Thomas-Davies N, Thornton A, Turnyanskiy MR, Valovic M, Vann RGL, Verwichte E, Voskoboynikov P, Voss G, Warder SEV, Wilson HR, Wodniak I, Zoletnik S, Zagorski Ret al., 2013, Overview of physics results from MAST towards ITER/DEMO and the MAST Upgrade, NUCLEAR FUSION, Vol: 53, ISSN: 0029-5515

JOURNAL ARTICLE

Highcock EG, Schekochihin AA, Cowley SC, Barnes M, Parra FI, Roach CM, Dorland Wet al., 2012, Zero-Turbulence Manifold in a Toroidal Plasma, PHYSICAL REVIEW LETTERS, Vol: 109, ISSN: 0031-9007

JOURNAL ARTICLE

Schekochihin AA, Highcock EG, Cowley SC, 2012, Subcritical fluctuations and suppression of turbulence in differentially rotating gyrokinetic plasmas, PLASMA PHYSICS AND CONTROLLED FUSION, Vol: 54, ISSN: 0741-3335

JOURNAL ARTICLE

Barnes M, Parra FI, Highcock EG, Schekochihin AA, Cowley SC, Roach CMet al., 2011, Turbulent Transport in Tokamak Plasmas with Rotational Shear, PHYSICAL REVIEW LETTERS, Vol: 106, ISSN: 0031-9007

JOURNAL ARTICLE

Highcock EG, Barnes M, Parra FI, Schekochihin AA, Roach CM, Cowley SCet al., 2011, Transport bifurcation induced by sheared toroidal flow in tokamak plasmas, PHYSICS OF PLASMAS, Vol: 18, ISSN: 1070-664X

JOURNAL ARTICLE

Kunz MW, Schekochihin AA, Cowley SC, Binney JJ, Sanders JSet al., 2011, A thermally stable heating mechanism for the intracluster medium: turbulence, magnetic fields and plasma instabilities, MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Vol: 410, Pages: 2446-2457, ISSN: 0035-8711

JOURNAL ARTICLE

Lloyd B, Akers RJ, Alladio F, Allan S, Appel LC, Barnes M, Barratt NC, Ben Ayed N, Breizman BN, Cecconello M, Challis CD, Chapman IT, Ciric D, Colyer G, Connor JW, Conway NJ, Cox M, Cowley SC, Cunningham G, Darke A, De Bock M, Delchambre E, De Temmerman G, Dendy RO, Denner P, Driscoll MD, Dudson B, Dunai D, Dunstan M, Elmore S, Field AR, Fishpool G, Freethy S, Garzotti L, Gibson KJ, Gryaznevich MP, Guttenfelder W, Harrison J, Hastie RJ, Hawkes NC, Hender TC, Hnat B, Howell DF, Hua M-D, Hubbard A, Huysmans G, Keeling D, Kim YC, Kirk A, Liang Y, Lilley MK, Lisak M, Lisgo S, Liu YQ, Maddison GP, Maingi R, Manhood SJ, Martin R, McArdle GJ, McCone J, Meyer H, Michael C, Mordijck S, Morgan T, Morris AW, Muir DG, Nardon E, Naylor G, O'Brien MR, O'Gorman T, Palenik J, Patel A, Pinches SD, Price MN, Roach CM, Rozhansky V, Saarelma S, Sabbagh SA, Saveliev A, Scannell R, Sharapov SE, Shevchenko V, Shibaev S, Stork D, Storrs J, Suttrop W, Sykes A, Tamain P, Taylor D, Temple D, Thomas-Davies N, Thornton A, Turnyanskiy MR, Valovic M, Vann RGL, Voss G, Walsh MJ, Warder SEV, Wilson HR, Windridge M, Wisse M, Zoletnik Set al., 2011, Overview of physics results from MAST, NUCLEAR FUSION, Vol: 51, ISSN: 0029-5515

JOURNAL ARTICLE

Parra FI, Barnes M, Highcock EG, Schekochihin AA, Cowley SCet al., 2011, Momentum Injection in Tokamak Plasmas and Transitions to Reduced Transport, PHYSICAL REVIEW LETTERS, Vol: 106, ISSN: 0031-9007

JOURNAL ARTICLE

Rosin MS, Schekochihin AA, Rincon F, Cowley SCet al., 2011, A non-linear theory of the parallel firehose and gyrothermal instabilities in a weakly collisional plasma, MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Vol: 413, Pages: 7-38, ISSN: 0035-8711

JOURNAL ARTICLE

Schekochihin AA, Highcock EG, Cowley SC, 2011, Suppression of turbulence and subcritical fluctuations in differentially rotating gyrokinetic plasmas, PPCF, Vol: 54

Differential rotation is known to suppress linear instabilities in fusionplasmas. However, even in the absence of growing eigenmodes, subcriticalfluctuations that grow transiently can lead to sustained turbulence. Heretransient growth of electrostatic fluctuations driven by the parallel velocitygradient (PVG) and the ion temperature gradient (ITG) in the presence of aperpendicular ExB velocity shear is considered. The maximally simplified caseof zero magnetic shear is treated in the framework of a local shearing box.There are no linearly growing eigenmodes, so all excitations are transient. Themaximal amplification factor of initial perturbations and the correspondingwavenumbers are calculated as functions of q/\epsilon (=safety factor/aspectratio), temperature gradient and velocity shear. Analytical results arecorroborated and supplemented by linear gyrokinetic numerical tests. Forsufficiently low values of q/\epsilon (<7 in our model), regimes with fullysuppressed ion-scale turbulence are possible. For cases when turbulence is notsuppressed, an elementary heuristic theory of subcritical PVG turbulenceleading to a scaling of the associated ion heat flux with q, \epsilon, velocityshear and temperature gradient is proposed; it is argued that the transport ismuch less stiff than in the ITG regime.

JOURNAL ARTICLE

Brown B, Forest C, Nornberg M, Zweibel E, Cattaneo F, Cowley Set al., 2010, An Experimental Plasma Dynamo Program for Investigations of Fundamental Processes in Heliophysics

Plasma experiments in laboratory settings offer unique opportunities toaddress fundamental aspects of the solar dynamo and magnetism in the solaratmosphere. We argue here that ground-based laboratory experiments have directconnections to NASA based missions and NSF programs, and that a smallinvestment in laboratory heliophysics may have a high payoff. We advocate forbroad involvement in community-scale plasma experiments.

JOURNAL ARTICLE

Cowley S, 2010, Hot fusion, PHYSICS WORLD, Vol: 23, Pages: 46-51, ISSN: 0953-8585

JOURNAL ARTICLE

Highcock EG, Barnes M, Schekochihin AA, Parra FI, Roach CM, Cowley SCet al., 2010, Transport Bifurcation in a Rotating Tokamak Plasma, PHYSICAL REVIEW LETTERS, Vol: 105, ISSN: 0031-9007

JOURNAL ARTICLE

Newton SL, Cowley SC, Loureiro NF, 2010, Understanding the effect of sheared flow on microinstabilities, PLASMA PHYSICS AND CONTROLLED FUSION, Vol: 52, ISSN: 0741-3335

JOURNAL ARTICLE

Plunk GG, Cowley SC, Schekochihin AA, Tatsuno Tet al., 2010, Two-dimensional gyrokinetic turbulence, JOURNAL OF FLUID MECHANICS, Vol: 664, Pages: 407-435, ISSN: 0022-1120

JOURNAL ARTICLE

Schekochihin AA, Cowley SC, Rincon F, Rosin MSet al., 2010, Magnetofluid dynamics of magnetized cosmic plasma: firehose and gyrothermal instabilities, MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Vol: 405, Pages: 291-300, ISSN: 0035-8711

JOURNAL ARTICLE

Smith CL, Cowley S, 2010, The path to fusion power, PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES, Vol: 368, Pages: 1091-1108, ISSN: 1364-503X

JOURNAL ARTICLE

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