Issue |
A&A
Volume 406, Number 1, July IV 2003
|
|
---|---|---|
Page(s) | L5 - L8 | |
Section | Letters | |
DOI | https://doi.org/10.1051/0004-6361:20030818 | |
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
Received:
26
March
2003
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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