Dear Ignacio,
Thanks for the preprint. I guess this is the same work we had an interesting discussion at the Napa meeting back in December. The results are intriguing, especially the dependence of the loop lifetimes on the temperature. However, you probably realize (better than we all) how many loops intersect in the fore- and background of the line-of-sight where you choose a box and plot a lightcurve to derive the lifetime. I have the impression that most lightcurves contain emission from multiple loops, but I admit that it is very difficult to disentangle them. It would be interesting if we could isolate individual loops by proper geometric (cross-sectional+background) modeling in all filters to see if your preliminary results hold up. Keep us posted about further progress!
Cheers, Markus
On Jan 9, 2009, at 5:54 AM, Ignacio Ugarte Urra wrote:
Hi all,
Just wanted to let you know about a paper on EIS/XRT observations of coronal loops just accepted by ApJ.
http://arxiv.org/abs/0901.1075
Title: "Active region transition region loop populations and their relationship to the corona" Authors: Ignacio Ugarte-Urra, Harry P. Warren and David H. Brooks
Abstract: The relationships among coronal loop structures at different temperatures is not settled. Previous studies have suggested that coronal loops in the core of an active region are not seen cooling through lower temperatures and therefore are steadily heated. If loops were cooling, the transition region would be an ideal temperature regime to look for a signature of their evolution. The Extreme-ultraviolet Imaging Spectrometer (EIS) on Hinode provides monochromatic images of the solar transition region and corona at an unprecedented cadence and spatial resolution, making it an ideal instrument to shed light on this issue. Analysis of observations of active region 10978 taken in 2007 December 8 -- 19 indicates that there are two dominant loop populations in the active region: core multi-temperature loops that undergo a continuous process of heating and cooling in the full observed temperature range 0.4-2.5 MK and even higher as shown by the X-Ray Telescope (XRT); and peripheral loops which evolve mostly in the temperature range 0.4-1.3 MK. Loops at transition region temperatures can reach heights of 150 Mm in the corona above the limb and develop downflows with velocities in the range of 39-105 km/s.
Best, Ignacio -- ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ Ignacio Ugarte-Urra ~ Naval Research Laboratory. Code 7673U. 4555 Overlook Ave SW. Washington, DC 20375 Contractor. Spain. phone: (+1) 202 404 1779 email: iugarte@ssd5.nrl.navy.mil http: http://tcrb.nrl.navy.mil/~iuu ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
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