Hot spine loops and the nature of a late-phase solar flare

Sun, X., Hoeksema, J.T., Liu, Y., Aulanier, G., Su, Y., Hannah, I.G. and Hock, R. (2013) Hot spine loops and the nature of a late-phase solar flare. Astrophysical Journal, 778(2), Art. 139. (doi: 10.1088/0004-637X/778/2/139)

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The fan-spine magnetic topology is believed to be responsible for many curious features in solar explosive events. A spine field line links distinct flux domains, but direct observation of such a feature has been rare. Here we report a unique event observed by the Solar Dynamic Observatory where a set of hot coronal loops (over 10 MK) connected to a quasi-circular chromospheric ribbon at one end and a remote brightening at the other. Magnetic field extrapolation suggests that these loops are partly tracers of the evolving spine field line. Continuous slipping- and null-point-type reconnections were likely at work, energizing the loop plasma and transferring magnetic flux within and across the fan quasi-separatrix layer. We argue that the initial reconnection is of the ''breakout'' type, which then transitioned to a more violent flare reconnection with an eruption from the fan dome. Significant magnetic field changes are expected and indeed ensued. This event also features an extreme-ultraviolet (EUV) late phase, i.e., a delayed secondary emission peak in warm EUV lines (about 2-7 MK). We show that this peak comes from the cooling of large post-reconnection loops beside and above the compact fan, a direct product of eruption in such topological settings. The long cooling time of the large arcades contributes to the long delay; additional heating may also be required. Our result demonstrates the critical nature of cross-scale magnetic coupling\mdashtopological change in a sub-system may lead to explosions on a much larger scale.

Item Type:Articles
Keywords:Sun: activity, Sun: corona, Sun: flares, Sun: magnetic fields, Sun: UV radiation
Glasgow Author(s) Enlighten ID:Hannah, Dr Iain
Authors: Sun, X., Hoeksema, J.T., Liu, Y., Aulanier, G., Su, Y., Hannah, I.G., and Hock, R.
Subjects:Q Science > QB Astronomy
College/School:College of Science and Engineering > School of Physics and Astronomy
Research Group:Astronomy & Astrophyiscs
Journal Name:Astrophysical Journal
ISSN (Online):1538-4357

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
542081Rolling Programme in Solar and Plasma AstrophysicsLyndsay FletcherScience & Technologies Facilities Council (STFC)ST/I001808/1P&A - PHYSICS & ASTRONOMY