34th Solar Physics Division Meeting, June 2003
Session 17 Corona III
Poster, Wednesday, June 18, 2003, 3:30-5:00pm, Mezzanine

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[17.01] A New Method to Constrain the Iron Abundance from Cooling Delays in Coronal Loops

M.J. Aschwanden, C.J. Schrijver (Locheed Martin, Solar & Astrophysics Lab.), A.R. Winebarger, H.P. Warren (Naval Research Laboratory)

Recent observations with TRACE reveal that the time delay between the appearance of a cooling loop in different EUV temperature filters is proportional to the loop length, dt12 ~ L . We model this cooling delay in terms of radiative loss and confirm this linear relationship theoretically. We derive an expression that can be used to constrain the coronal iron enhancement AFe=AFecor/AFePh relative to the photospheric value as function of the cooling delay dt12, flux F2, loop width w, and filling factor qw < 1. With this relation we find upper limits on the iron abundance enhancement of AFe < 4.8 +/- 1.7 for 10 small-scale nanoflare loops, and AFe < 1.4 +/- 0.4 for 5 large-scale loops, in the temperature range of T ~ 1.0-1.4 MK. This result supports the previous finding that low-FIP elements, including Fe, are enhanced in the corona. The same relation constitutes also a lower limit for the filling factor, which is qw > 0.2 +/- 0.1 and qw > 0.8 +/- 0.2 for the two groups of coronal loops.

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The author(s) of this abstract have provided an email address for comments about the abstract: aschwanden@lmsal.com

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Bulletin of the American Astronomical Society, 35 #3
© 2003. The American Astronomical Soceity.