White-Light Coronal Dark Threads and Density Fine Structure
1996; IOP Publishing; Volume: 466; Linguagem: Inglês
10.1086/177528
ISSN1538-4357
Autores Tópico(s)Geophysics and Gravity Measurements
Resumoview Abstract Citations (84) References (28) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS White-Light Coronal Dark Threads and Density Fine Structure November, Laurence J. ; Koutchmy, Serge Abstract High spatial resolution white-light coronal observations from the eclipse of 1991 July 11 taken with the 3.6 m Canada-France-Hawaii Telescope on Mauna Kea are the best ever achieved because of the unique opportunity of observing the totally eclipsed Sun with a large aperture telescope. Photometric calibration of the photographic data is verified by the average radial intensity variation, which agrees with the classical function. Dividing out the average radial variation, we identify relatively dark and bright fine "threads" with enhanced spatial power in the range of 1-5 Mm. Spatial filtering using unsharp masking or "mad-max" algorithms clearly shows relatively dark and bright radial threads in loops as fine as the resolution limit of about 1 Mm. The main feature is an arcade of concentric dark and bright threads that extend above a small prominence just above the limb. A small coronal cavity near the prominence contains numerous fine dark threads. The relative electron-density depletion and enhancement required to explain the observed thread contrast, assuming that they are isolated cylindrically symmetric structures, is found to be ΔNe/Ne ∼ ± 100%, indicating that the dark threads are fully evacuated. An excess of approximately 1 G field strength in stationary non-force-free magnetic fields can produce the observed thread contrast. Evacuated threads representing non-force-free magnetic fields introduce special constraints on the coronal thermodynamics. Publication: The Astrophysical Journal Pub Date: July 1996 DOI: 10.1086/177528 Bibcode: 1996ApJ...466..512N Keywords: ECLIPSES; SUN: CORONA full text sources ADS |
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