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C.J. Schrijver, A.W. Sandman, M.L. DeRosa, M.J. Aschwanden (Lockheed Martin Advanced Technology Center, Palo Alto, CA)
The appearance of the corona as viewed by different instruments, as well as its global spectral irradiance, sensitively depends on how coronal heating scales with the properties of the coronal magnetic field. We explore a variety of scaling dependences by simulating the appearance of the full-disk solar corona as viewed by SOHO/EIT and by YOHKOH/SXT, based on observed photospheric magnetic fields combined with a potential-field source-surface model. This leads us to conclude that the best match to X-ray and EUV observations of the corona over active regions and their environments is found for a heating flux density going into the corona that scales linearly with the field strength at the coronal base and roughly inversely with loop length. This scaling points to DC reconnection at tangential discontinuities as the most likely coronal heating mechanism, provided that the reconnection progresses at a rate proportional to the Alfven velocity. We also find that the best-fit coronal filling factor equals unity, suggesting that most of the corona is heated most of the time. We find evidence that loops with half lengths exceeding approximately 100,000 km are heated significantly more than suggested by the above scaling, possibly commensurate with the power deposited in the open field of coronal holes.
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Bulletin of the American Astronomical Society, 36 #2
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