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Explaining Warm Coronal LoopsOne of the great mysteries of coronal physics that has come to light in the last few years is the discovery that warn (- 1 INK) coronal loops are much denser than expected for quasi-static equilibrium. Both the excess densities and relatively long lifetimes of the loops can be explained with bundles of unresolved strands that are heated impulsively to very high temperatures. Since neighboring strands are at different stages of cooling, the composite loop bundle is multi-thermal, with the distribution of temperatures depending on the details of the "nanoflare storm." Emission hotter than 2 MK is predicted, but it is not clear that such emission is always observed. We consider two possible explanations for the existence of over-dense warm loops without corresponding hot emission: (1) loops are bundles of nanoflare heated strands, but a significant fraction of the nanoflare energy takes the form of a nonthermal electron beam rather then direct plasma heating; (2) loops are bundles of strands that undergo thermal nonequilibrium that results when steady heating is sufficiently concentrated near the footpoints. We present numerical hydro simulations of both of these possibilities and explore the observational consequences, including the production of hard X-ray emission and absorption by cool material in the corona.
Document ID
20080030145
Acquisition Source
Goddard Space Flight Center
Document Type
Conference Paper
Authors
Klimchuk, James A.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Karpen, Judy T.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Patsourakos, Spiros
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Date Acquired
August 24, 2013
Publication Date
May 25, 2008
Subject Category
Solar Physics
Meeting Information
Meeting: Joint meeting of AAS/SPD and American Geophysics Union (AGU)
Location: Fort Lauderdale, FL
Country: United States
Start Date: May 25, 2008
End Date: May 31, 2008
Sponsors: American Geophysical Union, American Astronomical Society
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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