Publications


Cosmic Ray Acceleration in Hydromagnetic Flux Tubes

Monthly Notices of the Royal Astronomical Society Oxford University Press (OUP) (2019)

A BELL, J Matthews, K Blundell, A Araudo

We find that hydromagnetic flux tubes in back-flows in the lobes of radio galaxies offer a suitable environment for the acceleration of cosmic rays (CR) to ultra-high energies. We show that CR can reach the Hillas (1984) energy even if the magnetised turbulence in the flux tube is not sufficiently strong for Bohm diffusion to apply. First-order Fermi acceleration by successive weak shocks in a hydromagnetic flux tube is shown to be equivalent to second-order Fermi acceleration by strong turbulence.


The origin of radio emission in broad absorption line quasars: Results from the LOFAR Two-metre Sky Survey

ASTRONOMY & ASTROPHYSICS 622 (2019) ARTN A15

LK Morabito, JH Matthews, PN Best, G Gurkan, MJ Jarvis, I Prandoni, KJ Duncan, MJ Hardcastle, M Kunert-Bajraszewska, AP Mechev, S Mooney, J Sabater, HJA Rottgering, TW Shimwell, DJB Smith, C Tasse, WL Williams


stella: An operator-split, implicit-explicit delta f-gyrokinetic code for general magnetic field configurations

JOURNAL OF COMPUTATIONAL PHYSICS 391 (2019) 365-380

M Barnes, FI Parra, M Landreman


Validation of gyrokinetic simulations of a National Spherical Torus eXperiment H-mode plasma and comparisons with a high-k scattering synthetic diagnostic

Plasma Physics and Controlled Fusion IOP Publishing 61 (2019) 115015-115015

JR Ruiz, W Guttenfelder, AE White, NT Howard, J Candy, Y Ren, DR Smith, NF Loureiro, C Holland, CW Domier


Ultrahigh energy cosmic rays from shocks in the lobes of powerful radio galaxies

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 482 (2019) 4303-4321

JH Matthews, AR Bell, KM Blundell, AT Araudo


Overview of recent TJ-II stellarator results

NUCLEAR FUSION 59 (2019) ARTN 112019

E Ascasibar, D Alba, D Alegre, A Alonso, J Alonso, F de Aragon, A Baciero, JM Barcala, E Blanco, J Botija, L Bueno, S Cabrera, E de la Cal, I Calvo, A Cappa, D Carralero, R Carrasco, B Carreras, F Castejon, R Castro, A de Castro, G Catalan, AA Chmyga, M Chamorro, AW Cooper, A Dinklage, L Eliseev, T Estrada, M Ezzat, F Fernandez-Marina, JM Fontdecaba, L Garcia, I Garcia-Cortes, R Garcia-Gomez, JM Garcia-Regana, A Gonzalez-Jerez, G Grenfell, J Guasp, J Hernandez-Sanchez, J Hernanz, C Hidalgo, E Hollmann, A Jimenez-Denche, P Khabanov, N Kharchev, I Kirpitchev, R Kleiber, AS Kozachek, L Krupnik, F Lapayese, M Liniers, B Liu, D Lopez-Bruna, A Lopez-Fraguas, B Lopez-Miranda, J Lopez-Razola, U Losada, E de la Luna, A Martin de Aguilera, F Martin-Diaz, M Martinez-Fuentes, G Martin-Gomez, AB Martin-Rojo, J Martinez-Fernandez, KJ McCarthy, F Medina, M Medrano, L Melon, AV Melnikov, P Mendez, R Merino, FJ Miguel, B van Milligen, A Molinero, B Momo, P Monreal, S Mulas, Y Narushima, M Navarro, M Ochando, S Ohshima, J Olivares, E Oyarzabal, JL de Pablos, L Pacios, N Panadero, F Parra, I Pastor, A de la Pena, A Pereira, JR Pinzon, AB Portas, E Poveda, JA Quintana, FJ Ramos, GA Ratta, M Redondo, E Rincon, L Rios, C Rodriguez-Fernandez, L Rodriguez-Rodrigo, B Rojo, A Ros, E Rosa, E Sanchez, J Sanchez, M Sanchez, E Sanchez-Sarabia, S Satake, JA Sebastian, R Sharma, C Silva, ER Solano, A Soleto, BJ Sun, FL Tabares, D Tafalla, H Takahashi, N Tamura, A Tolkachev, J Vega, G Velasco, JL Velasco, S Yamamoto, B Zurro, TJ-Team


Suppressed effective viscosity in the bulk intergalactic plasma

NATURE ASTRONOMY 3 (2019) 832-837

I Zhuravleva, E Churazov, AA Schekochihin, SW Allen, A Vikhlinin, N Werner


Intrinsic rotation driven by turbulent acceleration

PLASMA PHYSICS AND CONTROLLED FUSION 61 (2019) ARTN 025003

M Barnes, FI Parra


The Quick and the Dead: Finding the Surviving Binary Companions of Galactic Supernovae with Gaia

ASTROPHYSICAL JOURNAL 871 (2019) ARTN 92

M Fraser, D Boubert


Lessons from the curious case of the ‘fastest’ star in Gaia DR2

Monthly Notices of the Royal Astronomical Society Oxford University Press (OUP) 486 (2019) 2618-2630

D Boubert, J Strader, D Aguado, G Seabroke, SE Koposov, JL Sanders, S Swihart, L Chomiuk, NW Evans


A Magellanic origin for the Virgo sub-structure

Monthly Notices of the Royal Astronomical Society Oxford University Press (OUP) 482 (2019) 4562-4569

D Boubert, V Belokurov, D Erkal, G Iorio


A hypervelocity star with a Magellanic origin

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 483 (2019) 2007-2013

D Erkal, D Boubert, A Gualandris, NW Evans, F Antonini


MADE: a spectroscopic mass, age, and distance estimator for red giant stars with Bayesian machine learning

Monthly Notices of the Royal Astronomical Society Oxford University Press (OUP) 484 (2019) 294-304

P Das, JL Sanders


$\texttt{stella}$: a mixed implicit-explicit, delta-f gyrokinetic code for general magnetic field configurations

Journal of Computational Physics Elsevier (2019)

M Barnes, F Parra-Diaz, M Landreman

Here we present details of a mixed implicit-explicit numerical scheme for the solution of the gyrokinetic-Poisson system of equations in the local limit. This scheme has been implemented in a new code called $\texttt{stella}$, which is capable of evolving electrostatic fluctuations with full kinetic electron effects and an arbitrary number of ion species in general magnetic geometry. We demonstrate the advantages of this mixed approach over a fully explicit treatment and provide linear and nonlinear benchmark comparisons for both axisymmetric and non-axisymmetric magnetic equilibria.


Supersonic plasma turbulence in the laboratory.

Nature communications 10 (2019) 1758-

TG White, MT Oliver, P Mabey, M Kühn-Kauffeldt, AFA Bott, LNK Döhl, AR Bell, R Bingham, R Clarke, J Foster, G Giacinti, P Graham, R Heathcote, M Koenig, Y Kuramitsu, DQ Lamb, J Meinecke, T Michel, F Miniati, M Notley, B Reville, D Ryu, S Sarkar, Y Sakawa, MP Selwood, J Squire, RHH Scott, P Tzeferacos, N Woolsey, AA Schekochihin, G Gregori

The properties of supersonic, compressible plasma turbulence determine the behavior of many terrestrial and astrophysical systems. In the interstellar medium and molecular clouds, compressible turbulence plays a vital role in star formation and the evolution of our galaxy. Observations of the density and velocity power spectra in the Orion B and Perseus molecular clouds show large deviations from those predicted for incompressible turbulence. Hydrodynamic simulations attribute this to the high Mach number in the interstellar medium (ISM), although the exact details of this dependence are not well understood. Here we investigate experimentally the statistical behavior of boundary-free supersonic turbulence created by the collision of two laser-driven high-velocity turbulent plasma jets. The Mach number dependence of the slopes of the density and velocity power spectra agree with astrophysical observations, and supports the notion that the turbulence transitions from being Kolmogorov-like at low Mach number to being more Burgers-like at higher Mach numbers.


A scale-separated approach for studying coupled ion and electron scale turbulence

Plasma Physics and Controlled Fusion IOP Publishing (0)

MR Hardman, M Barnes, CM Roach, FI Parra


Overview of new MAST physics in anticipation of first results from MAST Upgrade

NUCLEAR FUSION 59 (2019) ARTN 112011

JR Harrison, RJ Akers, SY Allan, JS Allcock, JO Allen, L Appel, M Barnes, N Ben Ayedl, W Boeglin, C Bowman, J Bradley, P Browning, P Bryant, M Carr, M Cecconello, CD Challis, S Chapman, IT Chapman, GJ Colyer, S Conroy, NJ Conway, M Cox, G Cunningham, RO Dendy, W Dorland, BD Dudson, L Easy, SD Elmore, T Farley, X Feng, AR Field, A Fil, GM Fishpool, M Fitzgerald, K Flesch, MFJ Fox, H Frerichs, S Gadgil, D Gahle, L Garzotti, Y-C Ghim, S Gibson, KJ Gibson, S Hall, C Ham, N Heiberg, SS Henderson, E Highcock, B Hnat, J Howard, J Huang, SWA Irvine, AS Jacobsen, O Jones, I Katramados, D Keeling, A Kirk, I Klimek, L Kogan, J Leland, B Lipschultz, B Lloyd, J Lovell, B Madsen, O Marshall, R Martin, G McArdle, K McClements, B McMillan, A Meakins, HF Meyer, F Militello, J Milnes, S Mordijck, AW Morris, D Moulton, D Muir, K Mukhi, S Murphy-Sugrue, O Myatra, G Naylor, P Naylor, SL Newton, T O'Gorman, J Omotani, MG O'Mullane, S Orchard, SJP Pamela, L Pangione, F Parra, RV Perez, L Piron, M Price, ML Reinke, F Riva, CM Roach, D Robb, D Ryan, S Saarelma, M Salewski, S Scannell, AA Schekochihin, O Schmitz, S Sharapov, R Sharples, SA Silburn, SF Smith, A Sperduti, R Stephen, NT Thomas-Davies, AJ Thornton, M Turnyanskiy, M Valovic, F Van Wyk, RGL Vann, NR Walkden, I Waters, HR Wilson, MAST-U Team, EM Team


Field reconstruction from proton radiography of intense laser driven magnetic reconnection

PHYSICS OF PLASMAS 26 (2019) ARTN 083109

CAJ Palmer, PT Campbell, Y Ma, L Antonelli, AFA Bott, G Gregori, J Halliday, Y Katzir, P Kordell, K Krushelnick, SV Lebedev, E Montgomery, M Notley, DC Carroll, CP Ridgers, AA Schekochihin, MJV Streeter, AGR Thomas, ER Tubman, N Woolsey, L Willingale


Cosmic ray acceleration to ultrahigh energy in radio galaxies

EPJ Web of Conferences EDP Sciences (2019)

JH Matthews, AR Bell, AT Araudo, KM Blundell

The origin of ultrahigh energy cosmic rays (UHECRs) is an open question. In this proceeding, we first review the general physical requirements that a source must meet for acceleration to 10-100 EeV, including the consideration that the shock is not highly relativistic. We show that shocks in the backflows of radio galaxies can meet these requirements. We discuss a model in which giant-lobed radio galaxies such as Centaurus A and Fornax A act as slowly-leaking UHECR reservoirs, with the UHECRs being accelerated during a more powerful past episode. We also show that Centaurus A, Fornax A and other radio galaxies may explain the observed anisotropies in data from the Pierre Auger Observatory, before examining some of the difficulties in associating UHECR anisotropies with astrophysical sources.


The luminosity dependence of thermally driven disc winds in low-mass X-ray binaries

Monthly Notices of the Royal Astronomical Society 484 (2019) 4635-4644

N Higginbottom, C Knigge, KS Long, JH Matthews, EJ Parkinson

© 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. We have carried out radiation-hydrodynamic simulations of thermally driven accretion disc winds in low-mass X-ray binaries. Our main goal is to study the luminosity dependence of these outflows and compare with observations. The simulations span the range 0.04 ≤ L acc /L Edd ≤ 1.0 and therefore cover most of the parameter space in which disc winds have been observed. Using a detailed Monte Carlo treatment of ionization and radiative transfer, we confirm two key results found in earlier simulations that were carried out in the optically thin limit: (i) the wind velocity - and hence the maximum blueshift seen in wind-formed absorption lines - increases with luminosity; (ii) the large-scale wind geometry is quasi-spherical, but observable absorption features are preferentially produced along high-column equatorial sightlines. In addition, we find that (iii) the wind efficiency always remains approximately constant at skew4dotM-rm wind/skew4dotM-rm acc simeq 2, a behaviour that is consistent with observations. We also present synthetic Fe xxv and Fe xxvi absorption line profiles for our simulated disc winds in order to illustrate the observational implications of our results.

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