http://arxiv.org/abs/1611.02237
Magnetic reconnection and particle acceleration due to the kink instability in twisted coronal loops can be a viable scenario for confined solar flares. Detailed investigation of this phenomenon requires reliable methods for observational detection of magnetic twist in solar flares, which may not be possible solely through extreme UV and soft X-ray thermal emission. The gradient of microwave polarisation across flaring loops can serve as one of the detection criteria. The aim of this study is to investigate the effect of magnetic twist in flaring coronal loops on the polarisation of gyro-synchrotron microwave emission, and determine whether microwave emission polarisation could provide a means for observational detection. We use time-dependent magnetohydrodynamic and test-particle models, developed using LARE3D and GCA codes to investigate twisted coronal loops relaxing following the kink-instability, and calculate synthetic microwave emission maps (I and V Stokes components) using GX simulator. It is found that flaring twisted coronal loops would yield some characteristic observational patterns, such as a gradient of Stokes V parameter across the loop. However, these patterns may be visible only for a relatively short period of time due to fast magnetic reconfiguration after the instability. We find that normally they will be visible for only a minute after onset of magnetic reconnection (or after the beginning of the impulsive phase). The visibility will also depend on the orientation and position of the loop on solar disk. Typically, it would be difficult to see the characteristic polarisation pattern if the twisted loop is seen from the top (close to the centre of the solar disk), but easier if the twisted loop is seen from the side (i.e. observed very close to the limb).
M. Gordovskyy, P. Browning and E. Kontar
Tue, 8 Nov 16
74/75
Comments: Submitted to Astronomy & Astrophysics
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