Volume 406, Number 1, July IV 2003
|Page(s)||L5 - L8|
|Published online||17 November 2003|
Letter to the Editor
Solar active regions: The footpoints of 1 MK loops
Department of Applied Mathematics and Theoretical Physics, University of Cambridge, UK
Corresponding author: G.Del-Zanna@damtp.cam.ac.uk
Accepted: 31 May 2003
On-disc SOHO and TRACE observations of the footpoints of 1 MK quiescent loops in a solar active region are presented. These types of loops are long-lived and high-lying features that are best seen in the TRACE 173 Å passband, sensitive to 1 MK temperatures. SOHO/CDS data are used to show the clear association between the high-lying 1 MK coronal emission and emission formed at lower heights and temperatures, in the transition region. The 1 MK loops are rooted in strong unipolar regions located at the supergranular network boundaries. These loops have near-isothermal distributions at each location along their length, with peak emission measures at MK, where electron densities are ~ cm-3. The loops showed photospheric abundances, at odds with previous results based on Skylab data.
Key words: Sun: corona / Sun: transition region / Sun: abundances / techniques: spectroscopic
© ESO, 2003
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