Simulation Study of the Spreading/Elongation of Ribbons in Two-Ribbon Flares.
Abstract
Two-ribbon solar flares are characterized by the appearance in pairs of bright ribbons on the surface of the Sun. The ribbons separate from each other in time, which has been cited as one of many pieces of evidence that magnetic reconnection mediates the release of magnetic energy in solar flares. In addition to moving apart from each other, observations have revealed that ribbons also elongate (or spread) in time. This is thought to be related to the spreading of the magnetic reconnection process in the corona, but the phenomenon has not received as much attention as ribbon separation. There have been some studies of the spreading of magnetic reconnection using three-dimensional (3D) numerical simulations. A recent study revealed that localized reconnection spreads in the direction normal to the reconnection plane either unidirectionally or bidirectionally depending on the strength of the "guide" magnetic field along the direction of the current. Observations of flare ribbons also reveal that ribbons elongate either unidirectionally or bidirectionally with a similar dependence on the guide field, which suggests a strong connection with the numerical results. We further investigate the physics of reconnection spreading and its potential relation to two-ribbon flares via a parametric study using 3D two-fluid numerical simulations. We begin with studying the effects of having a non- uniform current sheet thickness on reconnection spreading. We find that reconnection spreads largely unimpeded in regions of low thickness and is either slowed down substantially or brought to a halt when the spreading reaches a region with a wider current sheet. The results may be useful not just for solar flares, but also Earth's magnetotail and laboratory reconnection experiments.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFMSH31B2560A
- Keywords:
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- 7599 General or miscellaneous;
- SOLAR PHYSICS;
- ASTROPHYSICS;
- AND ASTRONOMYDE: 7899 General or miscellaneous;
- SPACE PLASMA PHYSICSDE: 7999 General or miscellaneous;
- SPACE WEATHER