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A Model for the Origin of High Density in Loop-top X-ray Sources View all abstracts by submitter

Dana Longcope   Submitted: 2011-07-14 10:58

Super-hot looptop sources, detected in some large solar flares, are compactsources of HXR emission with spectra matching thermal electron populationsexceeding 30 megakelvins. High observed emission measure, as well as inferenceof electron thermalization within the small source region, both provideevidence of high densities at the looptop; typically more than an order ofmagnitude above ambient. Where some investigators have suggested such densityenhancement results from a rapid enhancement in the magnetic field strength, wepropose an alternative model, based on Petschek reconnection, whereby looptopplasma is heated and compressed by slow magnetosonic shocks generatedself-consistently through flux retraction following reconnection. Under steadyconditions such shocks can enhance density by no more than a factor of four.These steady shock relations (Rankine-Hugoniot relations) turn out to beinapplicable to Petschek's model owing to transient effects of thermalconduction. The actual density enhancement can in fact exceed a factor of tenover the entire reconnection outflow. An ensemble of flux tubes retractingfollowing reconnection at an ensemble of distinct sites will have a collectiveemission measure proportional to the rate of flux tube production. This rate,distinct from the local reconnection rate within a single tube, can be measuredseparately through flare ribbon motion. Typical flux transfer rates and loopparameters yield emission measures comparable to those observed in super-hotsources.

Authors: D.W. Longcope, S.E. Guidoni
Projects: None

Publication Status: ApJ (accepted)
Last Modified: 2011-07-14 15:24
Go to main E-Print page  Magnetic Energy Storage and Current Density Distributions for Different Force-Free Models  Anatomy of a solar flare: measurements of the December 14, 2006 X-class flare with GONG, Hinode and RHESSI  Edit Entry  Download Preprint  Delete Entry 

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