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Title: MAGNETIC FIELD TOPOLOGY AND THE THERMAL STRUCTURE OF THE CORONA OVER SOLAR ACTIVE REGIONS

Solar extreme ultraviolet (EUV) images of quiescent active-region coronae are characterized by ensembles of bright 1-2 MK loops that fan out from select locations. We investigate the conditions associated with the formation of these persistent, relatively cool, loop fans within and surrounding the otherwise 3-5 MK coronal environment by combining EUV observations of active regions made with TRACE with global source-surface potential-field models based on the full-sphere photospheric field from the assimilation of magnetograms that are obtained by the Michelson Doppler Imager (MDI) on SOHO. We find that in the selected active regions with largely potential-field configurations these fans are associated with (quasi-)separatrix layers (QSLs) within the strong-field regions of magnetic plage. Based on the empirical evidence, we argue that persistent active-region cool-loop fans are primarily related to the pronounced change in connectivity across a QSL to widely separated clusters of magnetic flux, and confirm earlier work that suggested that neither a change in loop length nor in base field strengths across such topological features are of prime importance to the formation of the cool-loop fans. We discuss the hypothesis that a change in the distribution of coronal heating with height may be involved in the phenomenon of relatively coolmore » coronal loop fans in quiescent active regions.« less
Authors:
; ;  [1]
  1. Lockheed Martin Advanced Technology Center, Palo Alto, CA 94304 (United States)
Publication Date:
OSTI Identifier:
21457109
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 719; Journal Issue: 2; Other Information: DOI: 10.1088/0004-637X/719/2/1083
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; 79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; EXTREME ULTRAVIOLET RADIATION; MAGNETIC FIELDS; MAGNETIC FLUX; SOLAR CORONA; SUN; SURFACE POTENTIAL ATMOSPHERES; ELECTROMAGNETIC RADIATION; MAIN SEQUENCE STARS; POTENTIALS; RADIATIONS; SOLAR ATMOSPHERE; STARS; STELLAR ATMOSPHERES; STELLAR CORONAE; ULTRAVIOLET RADIATION