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3D-Stereoscopic Analysis of Solar Active Region Loops: I: SoHo/EIT Observations at Temperatures of 1.0-1.5 MKThe three-dimensional (3D) structure of solar active region NOAA 7986 observed on 1996 August 30 with the Extrem-ultraviolet Imaging Telescope (EIT) onboard the Solar and Heliospheric Observatory (SoHO) is analyzed. We develop a new method of Dynamic Stereoscopy to reconstruct the 3D geometry of dynamically changing loops, which allows us to determine the orientation of the loop plane with respect to the line-of-sight, a prerequisite to correct properly for projection effects in 3D loop models. With this method and the filter-ratio technique applied to EIT 171 A and 195 A images we determine the 3D coordinates (x(s), y(s), z(s)), the loop width) w(s), the electron density n(sub e)(s), and the electron temperature T(sub e)(s) as function of the loop length s for 30 loop segments. Fitting the loop densities with an exponential density model n(sub e)(h) we find that the so inferred scale height temperatures, T(sub e)(sup lambda) = 1.22 +/- 0.23 MK, match closely the EIT filter-ratio temperatures, T(sub e)(sup FIT) = 1.21 +/- 0.06 MK. We conclude that these rather large-scale loops (with heights of h approx. equals 50 - 200 Mm) that dominate EIT 171 A images are close to thermal equilibrium. Most of the loops show no significant thickness variation w(s), but many exhibit a trend of increasing temperature (dT/ds greater than 0) above the footpoint.
Document ID
19980209714
Acquisition Source
Marshall Space Flight Center
Document Type
Reprint (Version printed in journal)
Authors
Aschwanden, Markus J. (Maryland Univ. College Park, MD United States)
Newmark, Jeff (NASA Goddard Space Flight Center Greenbelt, MD United States)
Delaboudiniere, Jean-Pierre (NASA Goddard Space Flight Center Greenbelt, MD United States)
Neupert, Werner M. (Hughes STX, Inc. Lanham, MD United States)
Portier-Fozzani, Fabrice (Centre National de la Recherche Scientifique Marseilles, France)
Gary, G. Allen (NASA Marshall Space Flight Center Huntsville, AL United States)
Zucker, Arik (Eidgenoessische Technische Hochschule Zurich, Switzerland)
Date Acquired
September 6, 2013
Publication Date
April 9, 1998
Publication Information
Publication: Astrophysical Journal: Manuscript Version
Subject Category
Solar Physics
Report/Patent Number
NAS 1.15:208103
NASA/TM-1998-208103
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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