Triggering magnetar outbursts in 3D force-free simulations

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Title: Triggering magnetar outbursts in 3D force-free simulations
Authors: Carrasco, Federico | Viganò, Daniele | Palenzuela, Carlos | Pons, José A.
Research Group/s: Astrofísica Relativista
Center, Department or Service: Universidad de Alicante. Departamento de Física Aplicada
Keywords: Plasmas | Magnetic reconnection | Stars: magnetars | Stars: magnetic field | Stars: flares | Methods: numerical
Knowledge Area: Astronomía y Astrofísica
Issue Date: 21-Mar-2019
Publisher: Oxford University Press
Citation: Monthly Notices of the Royal Astronomical Society. 2019, 484(1): L124-L129. doi:10.1093/mnrasl/slz016
Abstract: In this letter, we present the first 3D force-free general relativity simulations of the magnetosphere dynamics related to the magnetar outburst/flare phenomenology. Starting from an initial dipole configuration, we adiabatically increase the helicity by twisting the footprints of a spot on the stellar surface and follow the succession of quasi-equilibrium states until a critical twist is reached. Twisting beyond that point triggers instabilities that results in the rapid expansion of magnetic field lines, followed by reconnection, as observed in previous axi-symmetric simulations. If the injection of magnetic helicity goes on, the process is recurrent, periodically releasing a similar amount of energy, of the order of a few per cent of the total magnetic energy. From our current distribution, we estimate the local temperature assuming that dissipation occurs mainly in the highly resistive outermost layer of the neutron star. We find that the temperature smoothly increases with injected twist, being larger for spots located in the tropical regions than in polar regions, and rather independent of their sizes. After the injection of helicity ceases, the magnetosphere relaxes to a new stable state, in which the persistent currents maintain the footprints area slightly hotter than before the onset of the instability.
Sponsor: We acknowledge support from the Spanish Ministry of Economy, Industry, and Competitiveness grants AYA2016-80289-P and AYA2017-82089-ERC (AEI/FEDER, UE), and AYA2015-66899-C2-2-P. CP also acknowledges support from the Spanish Ministry of Education and Science through a Ramon y Cajal grant.
ISSN: 0035-8711 (Print) | 1365-2966 (Online)
DOI: 10.1093/mnrasl/slz016
Language: eng
Type: info:eu-repo/semantics/article
Rights: © 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society
Peer Review: si
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Appears in Collections:INV - Astrofísica Relativista - Artículos de Revistas

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