Theoretical astrophysics and plasma physics at RPC

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Multi-scale dynamics of magnetic flux tubes and inverse magnetic energy transfer

Journal of Plasma Physics Cambridge University Press (CUP) 86:4 (2020) 535860401

Authors:

Muni Zhou, Nuno F Loureiro, Dmitri A Uzdensky

Abstract:

We report on an analytical and numerical study of the dynamics of a three-dimensional array of identical magnetic flux tubes in the reduced-magnetohydrodynamic description of the plasma. We propose that the long-time evolution of this system is dictated by flux-tube mergers, and that such mergers are dynamically constrained by the conservation of the pertinent (ideal) invariants,viz.the magnetic potential and axial fluxes of each tube. We also propose that in the direction perpendicular to the merging plane, flux tubes evolve in a critically balanced fashion. These notions allow us to construct an analytical model for how quantities such as the magnetic energy and the energy-containing scale evolve as functions of time. Of particular importance is the conclusion that, like its two-dimensional counterpart, this system exhibits an inverse transfer of magnetic energy that terminates only at the system scale. We perform direct numerical simulations that confirm these predictions and reveal other interesting aspects of the evolution of the system. We find, for example, that the early time evolution is characterized by a sharp decay of the initial magnetic energy, which we attribute to the ubiquitous formation of current sheets. We also show that a quantitatively similar inverse transfer of magnetic energy is observed when the initial condition is a random, small-scale magnetic seed field.
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Time-resolved fast turbulent dynamo in a laser plasma

(2020)

Authors:

AFA Bott, P Tzeferacos, L Chen, CAJ Palmer, A Rigby, A Bell, R Bingham, A Birkel, C Graziani, DH Froula, J Katz, M Koenig, MW Kunz, CK Li, J Meinecke, F Miniati, R Petrasso, H-S Park, BA Remington, B Reville, JS Ross, D Ryu, D Ryutov, F Séguin, TG White, AA Schekochihin, DQ Lamb, G Gregori
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The shearing sheet and swing amplification revisited

Monthly Notices of the Royal Astronomical Society Oxford University Press (OUP) 496:1 (2020) 767-783
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Formation and Evolution of Compact-object Binaries in AGN Disks

ASTROPHYSICAL JOURNAL American Astronomical Society 898:1 (2020) ARTN 25

Authors:

Hiromichi Tagawa, Zoltan Haiman, Bence Kocsis
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Jeans modelling of the Milky Way's nuclear stellar disc

(2020)

Authors:

Mattia C Sormani, John Magorrian, Francisco Nogueras-Lara, Nadine Neumayer, Ralph Schoenrich, Ralf S Klessen, Alessandra Mastrobuono-Battisti
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