Publications


High-m kink/tearing modes in cylindrical geometry

PLASMA PHYSICS AND CONTROLLED FUSION 56 (2014) ARTN 125006

JW Connor, RJ Hastie, I Pusztai, PJ Catto, M Barnes


Effect on plasma rotation of lower hybrid (LH) waves in Alcator C-Mod

AIP Conference Proceedings 1580 (2014) 398-401

JP Lee, M Barnes, RR Parker, JE Rice, FI Parra, PT Bonoli, ML Reinke

The injection of LH waves for current drive into a tokamak changes the ion toroidal rotation. In Alcator C-Mod, the direction of the steady state rotation change due to LH waves depends on the plasma current and the density. The change in rotation can be estimated by balancing the external torque of lower hybrid waves with the turbulent radial transport of the momentum. For high plasma current, the turbulent pinch and diffusion of the injected counter-current momentum are sufficient to explain the rotation change. However, for low plasma current, the change in the the intrinsic momentum transport (residual stress) for a non-rotating state is required to explain the co-current rotation change. Accordingly, we investigate the intrinsic momentum transport for the non-rotating state when diamagnetic flow and ExB flow cancel each other. The change in the intrinsic momentum transport due to lower hybrid waves is significant when the plasma current is low, which may explain the rotation reversal for low plasma current. The effect of changed q (safety factor) profile by lower hybrid on the intrinsic momentum transport is estimated by gyrokinetics. © 2014 AIP Publishing LLC.


Observation of a new high- β and high-density state of a magnetospheric plasma in RT-1

Physics of Plasmas 21 (2014)

H Saitoh, Y Yano, Z Yoshida, M Nishiura, J Morikawa, Y Kawazura, T Nogami, M Yamasaki

A new high-β and high-density state is reported for a plasma confined in a laboratory magnetosphere. In order to expand the parameter regime of an electron cyclotron resonance heating experiment, the 8.2 GHz microwave power of the Ring Trap 1 device has been upgraded with the installation of a new waveguide system. The rated input power launched from a klystron was increased from 25 to 50 kW, which enabled the more stable formation of a hot-electron high-β plasma. The diamagnetic signal (the averaged value of four magnetic loops signals) of a plasma reached 5.2 mWb. According to a two-dimensional Grad-Shafranov analysis, the corresponding local β value is close to 100%. © 2014 AIP Publishing LLC.


Relabeling symmetry in relativistic fluids and plasmas

Journal of Physics A: Mathematical and Theoretical 47 (2014)

Y Kawazura, Z Yoshida, Y Fukumoto

© 2014 IOP Publishing Ltd. The conservation of the recently formulated relativistic canonical helicity (Yoshida et al 2014 J. Math. Phys. 55 043101) is derived from Noether's theorem by constructing an action principle on the relativistic Lagrangian coordinates (we obtain general cross helicities that include the helicity of the canonical vorticity). The conservation law is, then, explained by the relabeling symmetry pertinent to the Lagrangian label of fluid elements. Upon Eulerianizing the Noether current, the purely spatial volume integral on the Lagrangian coordinates is mapped to a space-time mixed three-dimensional integral on the four-dimensional Eulerian coordinates. The relativistic conservation law in the Eulerian coordinates is no longer represented by any divergence-free current; hence, it is not adequate to regard the relativistic helicity (represented by the Eulerian variables) as a Noether charge, and this stands the reason why the 'conventional helicity' is no longer a constant of motion. We have also formulated a relativistic action principle of magnetohydrodynamics (MHD) on the Lagrangian coordinates, and have derived the relativistic MHD cross helicity.


THE RELATION BETWEEN GAS DENSITY AND VELOCITY POWER SPECTRA IN GALAXY CLUSTERS: QUALITATIVE TREATMENT AND COSMOLOGICAL SIMULATIONS

ASTROPHYSICAL JOURNAL LETTERS 788 (2014) ARTN L13

I Zhuravleva, EM Churazov, AA Schekochihin, ET Lau, D Nagai, M Gaspari, SW Allen, K Nelson, IJ Parrish


Turbulent momentum pinch of diamagnetic flows in a tokamak

ArXiv (0)

J Lee, FI Parra, M Barnes

The ion toroidal rotation in a tokamak consists of an $E\times B$ flow due to the radial electric field and a diamagnetic flow due to the radial pressure gradient. The turbulent pinch of toroidal angular momentum due to the Coriolis force studied in previous work is only applicable to the $E\times B$ flow. In this Letter, the momentum pinch for the rotation generated by the radial pressure gradient is calculated and is compared with the Coriolis pinch. This distinction is important for subsonic flows or the flow in the pedestal where the two types of flows are similar in size and opposite in direction. In the edge, the different pinches due to the opposite rotations can result in intrinsic momentum transport that gives significant rotation peaking.


Actions, angles and frequencies for numerically integrated orbits

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 441 (2014) 3284-3295

JL Sanders, J Binney


Turbulent heating in galaxy clusters brightest in X-rays.

Nature 515 (2014) 85-87

I Zhuravleva, E Churazov, AA Schekochihin, SW Allen, P Arévalo, AC Fabian, WR Forman, JS Sanders, A Simionescu, R Sunyaev, A Vikhlinin, N Werner

The hot (10(7) to 10(8) kelvin), X-ray-emitting intracluster medium (ICM) is the dominant baryonic constituent of clusters of galaxies. In the cores of many clusters, radiative energy losses from the ICM occur on timescales much shorter than the age of the system. Unchecked, this cooling would lead to massive accumulations of cold gas and vigorous star formation, in contradiction to observations. Various sources of energy capable of compensating for these cooling losses have been proposed, the most promising being heating by the supermassive black holes in the central galaxies, through inflation of bubbles of relativistic plasma. Regardless of the original source of energy, the question of how this energy is transferred to the ICM remains open. Here we present a plausible solution to this question based on deep X-ray data and a new data analysis method that enable us to evaluate directly the ICM heating rate from the dissipation of turbulence. We find that turbulent heating is sufficient to offset radiative cooling and indeed appears to balance it locally at each radius-it may therefore be the key element in resolving the gas cooling problem in cluster cores and, more universally, in the atmospheres of X-ray-emitting, gas-rich systems on scales from galaxy clusters to groups and elliptical galaxies.


Constraining the Galaxy's dark halo with RAVE stars

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 445 (2014) 3133-3151

T Piffl, J Binney, PJ McMillan, M Steinmetz, A Helmi, RFG Wyse, O Bienayme, J Bland-Hawthorn, K Freeman, B Gibson, G Gilmore, EK Grebel, G Kordopatis, JF Navarro, Q Parker, WA Reid, G Seabroke, A Siebert, F Watson, T Zwitter


Using probabilistic sampling-based sensitivity analyses for indoor air quality modelling

BUILDING AND ENVIRONMENT 78 (2014) 171-182

P Das, C Shrubsole, B Jones, I Hamilton, Z Chalabi, M Davies, A Mavrogianni, J Taylor


Home energy efficiency and radon related risk of lung cancer: modelling study.

BMJ (Clinical research ed.) 348 (2014) f7493-

J Milner, C Shrubsole, P Das, B Jones, I Ridley, Z Chalabi, I Hamilton, B Armstrong, M Davies, P Wilkinson

OBJECTIVE: To investigate the effect of reducing home ventilation as part of household energy efficiency measures on deaths from radon related lung cancer. DESIGN: Modelling study. SETTING: England. INTERVENTION: Home energy efficiency interventions, motivated in part by targets for reducing greenhouse gases, which entail reduction in uncontrolled ventilation in keeping with good practice guidance. MAIN OUTCOME MEASURES: Modelled current and future distributions of indoor radon levels for the English housing stock and associated changes in life years due to lung cancer mortality, estimated using life tables. RESULTS: Increasing the air tightness of dwellings (without compensatory purpose-provided ventilation) increased mean indoor radon concentrations by an estimated 56.6%, from 21.2 becquerels per cubic metre (Bq/m(3)) to 33.2 Bq/m(3). After the lag in lung cancer onset, this would result in an additional annual burden of 4700 life years lost and (at peak) 278 deaths. The increases in radon levels for the millions of homes that would contribute most of the additional burden are below the threshold at which radon remediation measures are cost effective. Fitting extraction fans and trickle ventilators to restore ventilation will help offset the additional burden but only if the ventilation related energy efficiency gains are lost. Mechanical ventilation systems with heat recovery may lower radon levels and the risk of cancer while maintaining the advantage of energy efficiency for the most airtight dwellings but there is potential for a major adverse impact on health if such systems fail. CONCLUSION: Unless specific remediation is used, reducing the ventilation of dwellings will improve energy efficiency only at the expense of population wide adverse impact on indoor exposure to radon and risk of lung cancer. The implications of this and other consequences of changes to ventilation need to be carefully evaluated to ensure that the desirable health and environmental benefits of home energy efficiency are not compromised by avoidable negative impacts on indoor air quality.


Firehose and Mirror Instabilities in a Collisionless Shearing Plasma

PHYSICAL REVIEW LETTERS 112 (2014) ARTN 205003

MW Kunz, AA Schekochihin, JM Stone


A NEW STELLAR CHEMO-KINEMATIC RELATION REVEALS THE MERGER HISTORY OF THE MILKY WAY DISK

ASTROPHYSICAL JOURNAL LETTERS 781 (2014) ARTN L20

I Minchev, C Chiappini, M Martig, M Steinmetz, RS de Jong, C Boeche, C Scannapieco, T Zwitter, RFG Wyse, JJ Binney, J Bland-Hawthorn, O Bienayme, B Famaey, KC Freeman, BK Gibson, EK Grebel, G Gilmore, A Helmi, G Kordopatis, YS Lee, U Munari, JF Navarro, QA Parker, AC Quillen, WA Reid, A Siebert, A Siviero, G Seabroke, F Watson, M Williams


The diverse formation histories of simulated disc galaxies

Monthly Notices of the Royal Astronomical Society 441 (2014) 3679-3695

M Aumer, SDM White, T Naab

We analyse the formation histories of 19 galaxies from cosmological smoothed particle hydrodynamics zoom-in resimulations. We construct mock three-colour images and show that the models reproduce observed trends in the evolution of galaxy colours and morphologies. However, only a small fraction of galaxies contains bars. Many galaxies go through phases of central mass growth by in situ star formation driven by gas-rich mergers or misaligned gas infall. These events lead to accretion of low angular momentum gas to the centres and leave imprints on the distributions of z = 0 stellar circularities, radii and metallicities as functions of age. Observations of the evolution of structural properties of samples of disc galaxies at z = 2.5-0.0 infer continuous mass assembly at all radii. Our simulations can only explain this if there is a significant contribution from mergers or misaligned infall, as expected in a Λ cold dark matter universe. Quiescent merger histories lead to high kinematic disc fractions and inside-out growth, but show little central growth after the last 'destructive' merger at z > 1.5. For sufficiently strong feedback, as assumed in our models, a moderate amount of merging does not seem to be a problem for the z = 0 disc galaxy population, but may rather be a requirement. The average profiles of simulated disc galaxies agree with observations at z≥1.5. At z≤1, there is too much growth in size and too little growth in centralmass, possibly due to the underabundance of bars. The discrepancies may partly be caused by differences between the star formation histories of the simulations and those assumed for observations. © 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.


An observational and theoretical view of the radial distribution of HI gas in galaxies

Monthly Notices of the Royal Astronomical Society 441 (2014) 2159-2172

J Wang, J Fu, M Aumer, G Kauffmann, GIG Józsa, P Serra, ML Huang, J Brinchmann, T Van Der Hulst, F Bigiel

We analyse the radial distribution of HI gas for 23 disc galaxies with unusually high HI content from the Bluedisk sample, along with a similar-sized sample of 'normal' galaxies. We propose an empirical model to fit the radial profile of the HI surface density, an exponential function with a depression near the centre. The radial HI surface density profiles are very homogeneous in the outer regions of the galaxy; the exponentially declining part of the profile has a scalelength of ~0.18 R1, where R1 is the radius where the column density of the HI is 1 M⊙ pc -2 . This holds for all galaxies, independent of their stellar or HI mass. The homogenous outer profiles, combined with the limited range in HI surface density in the nonexponential inner disc, results in the well-known tight relation between HI size and HI mass. By comparing the radial profiles of the HI-rich galaxies with those of the control systems, we deduce that in about half the galaxies, most of the excess gas lies outside the stellar disc, in the exponentially declining outer regions of the HI disc. In the other half, the excess is more centrally peaked. We compare our results with existing smoothed particle hydrodynamical simulations and semi-analytic models of disc galaxy formation in a Λ cold dark matter universe. Both the hydro simulations and the semi-analytic models reproduce the HI surface density profiles and the HI size-mass relation without further tuning of the simulation and model inputs. In the semi-analytic models, the universal shape of the outer HI radial profiles is a consequence of the assumption that infalling gas is always distributed exponentially. © 2014 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.


Galactic kinematics and dynamics from Radial Velocity Experiment stars

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 439 (2014) 1231-1244

J Binney, B Burnett, G Kordopatis, M Steinmetz, G Gilmore, O Bienayme, J Bland-Hawthorn, B Famaey, EK Grebel, A Helmi, J Navarro, Q Parker, WA Reid, G Seabroke, A Siebert, F Watson, MEK Williams, RFG Wyse, T Zwitter


Erratum: Long-wavelength limit of gyrokinetics in a turbulent tokamak and its intrinsic ambipolarity (Plasma Phys. Control. Fusion (2012) 54 (115007))

Plasma Physics and Controlled Fusion 56 (2014)

I Calvo, FI Parra


Phase-space Lagrangian derivation of electrostatic gyrokinetics in general geometry (vol 53, 045001, 2011)

PLASMA PHYSICS AND CONTROLLED FUSION 56 (2014) ARTN 099501

FI Parra, I Calvo


Local dependence of ion temperature gradient on magnetic configuration, rotational shear and turbulent heat flux in MAST

NUCLEAR FUSION 54 (2014) ARTN 042003

Y-C Ghim, AR Field, AA Schekochihin, EG Highcock, C Michael, MAST Team


The RAVE survey: the Galactic escape speed and the mass of the Milky Way

ASTRONOMY & ASTROPHYSICS 562 (2014) ARTN A91

T Piffl, C Scannapieco, J Binney, M Steinmetz, R-D Scholz, MEK Williams, RS de Jong, G Kordopatis, G Matijevic, O Bienayme, J Bland-Hawthorn, C Boeche, K Freeman, B Gibson, G Gilmore, EK Grebel, A Helmi, U Munari, JF Navarro, Q Parker, WA Reid, G Seabroke, F Watson, RFG Wyse, T Zwitter

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