Shock corrugation by Rayleigh-Taylor instability in gamma-ray burst afterglow jets

Paul C. Duffell, Andrew I. MacFadyen

    Research output: Contribution to journalArticle

    Abstract

    Afterglow jets are Rayleigh-Taylor unstable and therefore turbulent during the early part of their deceleration. There are also several processes which actively cool the jet. In this Letter, we demonstrate that if cooling significantly increases the compressibility of the flow, the turbulence collides with the forward shock, destabilizing and corrugating it. In this case, the forward shock is turbulent enough to produce the magnetic fields responsible for synchrotron emission via small-scale turbulent dynamo. We calculate light curves assuming the magnetic field is in energy equipartition with the turbulent kinetic energy and discover that dynamic magnetic fields are well approximated by a constant magnetic-to-thermal energy ratio of 1%, though there is a sizeable delay in the time of peak flux as the magnetic field turns on only after the turbulence has activated. The reverse shock is found to be significantly more magnetized than the forward shock, with a magnetic-to-thermal energy ratio of the order of 10%. This work motivates future Rayleigh-Taylor calculations using more physical cooling models.

    Original languageEnglish (US)
    Article numberL1
    JournalAstrophysical Journal Letters
    Volume791
    Issue number1
    DOIs
    StatePublished - Aug 10 2014

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    Keywords

    • ISM: jets and outflows
    • gamma-ray burst: general
    • hydrodynamics
    • radiation mechanisms: non-thermal
    • shock waves
    • turbulence

    ASJC Scopus subject areas

    • Astronomy and Astrophysics
    • Space and Planetary Science

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