Polarisation of microwave emission from reconnecting twisted coronal loops

Mykola Gordovskyy, Philippa Browning, E P Kontar

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    Abstract

    Context. Magnetic reconnection and particle acceleration due to the kink instability in twisted coronal loops can be a viable scenario for conned solar
    ares. Detailed investigation of this phenomenon requires reliable methods for observational detection of magnetic twist in solar ares, which may not be possible solely through extreme UV and soft X-ray thermal emission. Polarisation of microwave emission in aring loops can be used as one of the detection criteria.

    Aims. The aim of this study is to investigate the eect of magnetic twist in aring coronal loops on the polarisation of gyro-synchrotron microwave (GSMW) emission, and determine whether it could provide a means for magnetic twist
    detection.

    Methods. We consider time-dependent magnetohydrodynamic and test-particle models developed using the LARE3D and GCA codes to investigate twisted coronal loops that relax after kink instability. Synthetic GSMW emission maps
    (I and V Stokes components) are calculated using GX simulator.

    Results. It is found that aring twisted coronal loops produce GSMW radiation with a gradient of circular polarisation across the loop. However, these patterns may be visible only for a relatively short period of time owing to fast magnetic
    reconguration after the instability. Their visibility also depends on the orientation and position of the loop on the solar disk. Typically, it would be dicult to see these characteristic polarisation patterns in a twisted loop seen from the top (i.e. close to the centre of the solar disk), but easier in a twisted loop seen from the side (i.e. observed very close to the limb).
    Original languageEnglish
    Article numbergsmw2016n2
    JournalAstronomy & Astrophysics
    Early online date12 Apr 2017
    DOIs
    Publication statusPublished - 2017

    Keywords

    • Sun: flares
    • Sun:EUV

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