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Title: An unorthodox X-Class Long-Duration Confined Flare

We report the observation of an X-class long-duration flare which is clearly confined. It appears as a compact-loop flare in the traditional EUV passbands (171 and 195 Å), but in the passbands sensitive to flare plasmas (94 and 131 Å), it exhibits a cusp-shaped structure above an arcade of loops like other long-duration events. Inspecting images in a running difference approach, we find that the seemingly diffuse, quasi-static cusp-shaped structure consists of multiple nested loops that repeatedly rise upward and disappear approaching the cusp edge. Over the gradual phase, we detect numerous episodes of loop rising, each lasting minutes. A differential emission measure analysis reveals that the temperature is highest at the top of the arcade and becomes cooler at higher altitudes within the cusp-shaped structure, contrary to typical long-duration flares. With a nonlinear force-free model, our analysis shows that the event mainly involves two adjacent sheared arcades separated by a T-type hyperbolic flux tube (HFT). One of the arcades harbors a magnetic flux rope, which is identified with a filament that survives the flare owing to the strong confining field. We conclude that a new emergence of magnetic flux in the other arcade triggers the flare, while the preexistingmore » HFT and flux rope dictate the structure and dynamics of the flare loops and ribbons during the long-lasting decay phase, and that a quasi-separatrix layer high above the HFT could account for the cusp-shaped structure.« less
Authors:
; ; ;  [1] ;  [2] ;  [3]
  1. CAS Key Laboratory of Geospace Environment, Department of Geophysics and Planetary Sciences, University of Science and Technology of China, Hefei 230026 (China)
  2. Predictive Science, Inc., 9990 Mesa Rim Road, Suite 170, San Diego, CA 92121 (United States)
  3. Space Weather Research Laboratory, Center for Solar-Terrestrial Research, NJIT, Newark, NJ 07102 (United States)
Publication Date:
OSTI Identifier:
22365637
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 790; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ALTITUDE; COMPACTS; DECAY; EMISSION; EXTREME ULTRAVIOLET RADIATION; FILAMENTS; HEAT EXCHANGERS; IMAGES; LAYERS; MAGNETIC FLUX; NONLINEAR PROBLEMS; PLASMA; SUN