Correlated Spatio-temporal Evolution of Extreme-Ultraviolet Ribbons and Hard X-rays in a Solar Flare
Abstract
We analyzed the structure and evolution of flare ribbons in the solar chromosphere to infer properties of coronal magnetic reconnection. We used ultraviolet (UV) imaging observations of the M7.3 SOL2014-04-18T13 flare obtained by IRIS and SDO/AIA, magnetic data from SDO/HMI, and hard X-ray (HXR) images from RHESSI and light curves from Fermi/GBM. Two flare ribbons spread away from the magnetic polarity inversion line as the event progressed. From high-resolution IRIS observations, we measured the width of the newly brightening front along the extension of the ribbon, which maps the feet of magnetic field lines reconnecting in the corona. We find that the ribbon front is highly intermittent in both space and time, presumably reflecting non-uniformities in the structure and/or dynamics of the flare current sheet. Early in the event, the ribbon fronts form and widen to near maximum thickness, and the rate of change of reconnected magnetic flux rises to its peak value. Subsequently, the flux change rate drops steeply, the UV light curves continue to rise toward their maxima, and the HXR emissions rise rapidly to their own maxima, which are simultaneous with those in the UV. We find indirect evidence that well-resolved local peaks in the UV ribbon-front widths are cospatial and cotemporal with the UV emissions and poorly resolved HXR emissions. This result suggests that there is a strong connection between the production of non-thermal electrons and locally enhanced perpendicular extent of flare ribbon fronts, which reflect the inhomogeneous structure and/or reconnection dynamics of the flare current sheet in the corona. We discuss the implications of these results for understanding the inhomogeneous structure and dynamics of the coronal flare current sheet and the origin of the flare-accelerated particles. NASA supported our research via the SOLFER DRIVE Center at UMD, the H-GI program at MSU, and the H-ISFM program at GSFC.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2021
- Bibcode:
- 2021AGUFMSH23B..05N