Physical role of topological constraints in localized magnetic relaxation

A. R. Yeates (Lead / Corresponding author), A. J. B. Russell, G. Hornig

    Research output: Contribution to journalArticle

    7 Citations (Scopus)

    Abstract

    Predicting the final state of turbulent plasma relaxation is an important challenge, both in astro-physical plasmas such as the Sun's corona and in controlled thermonuclear fusion. Recent numerical simulations of plasma relaxation with braided magnetic fields identified the possibility of a novel constraint, arising from the topological degree of the magnetic field-line mapping. This constraint implies that the final relaxed state is drastically different for an initial configuration with topological degree 1 (which allows a Taylor relaxation) and one with degree 2 (which does not reach a Taylor state). Here, we test this transition in numerical resistive-magnetohydrodynamic simulations, by embedding a braided magnetic field in a linear force-free background. Varying the background force-free field parameter generates a sequence of initial conditions with a transition between topological degree 1 and 2. For degree 1, the relaxation produces a single twisted flux tube, whereas for degree 2 we obtain two flux tubes. For predicting the exact point of transition, it is not the topological degree of the whole domain that is relevant, but only that of the turbulent region.
    Original languageEnglish
    Article number20150012
    Number of pages12
    JournalProceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences
    Volume471
    Issue number2178
    DOIs
    Publication statusPublished - 3 Jun 2015

    Fingerprint

    Magnetic relaxation
    Topological Degree
    magnetic relaxation
    Magnetic fields
    Plasmas
    Plasma
    Magnetic Field
    Fluxes
    Tube
    magnetic fields
    Magnetohydrodynamics
    tubes
    Sun
    magnetohydrodynamic simulation
    Corona
    Fusion reactions
    embedding
    coronas
    Fusion
    sun

    Keywords

    • Coronal heating
    • Magnetic topology
    • Magnetohydrodynamics
    • Plasma relaxation

    Cite this

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    abstract = "Predicting the final state of turbulent plasma relaxation is an important challenge, both in astro-physical plasmas such as the Sun's corona and in controlled thermonuclear fusion. Recent numerical simulations of plasma relaxation with braided magnetic fields identified the possibility of a novel constraint, arising from the topological degree of the magnetic field-line mapping. This constraint implies that the final relaxed state is drastically different for an initial configuration with topological degree 1 (which allows a Taylor relaxation) and one with degree 2 (which does not reach a Taylor state). Here, we test this transition in numerical resistive-magnetohydrodynamic simulations, by embedding a braided magnetic field in a linear force-free background. Varying the background force-free field parameter generates a sequence of initial conditions with a transition between topological degree 1 and 2. For degree 1, the relaxation produces a single twisted flux tube, whereas for degree 2 we obtain two flux tubes. For predicting the exact point of transition, it is not the topological degree of the whole domain that is relevant, but only that of the turbulent region.",
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    Physical role of topological constraints in localized magnetic relaxation. / Yeates, A. R. (Lead / Corresponding author); Russell, A. J. B.; Hornig, G.

    In: Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, Vol. 471, No. 2178, 20150012, 03.06.2015.

    Research output: Contribution to journalArticle

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    AU - Russell, A. J. B.

    AU - Hornig, G.

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