The Effect of Radiative Cooling on Coronal Loop Oscillations
Markus J. Aschwanden Submitted: 2008-09-02 14:16
Coronal loops that exhibit kink-mode oscillations have generally been assumed
to have a constant density and temperature during the observed time interval.
Analyzing their intensities in an EUV waveband, however, clearly shows
that their brightness varies in a way that is consistent with a
temperature cooling through the EUV passband, which limits their
detection time, observed damping time, and number of observable periods.
We study kink-mode oscillations of eight loops observed during the so-called
``harmonica event'' on 2001-Apr-15, 21:58-22:27 UT in 171 ang . We find
loop densities of n_e=(1.4±0.6) x 109 cm-3, loop widths of
w=2.0 ± 2.6 Mm, and e-folding cooling times of t_cool=17 ± 7 min,
when they cool through the peak temperature T=0.95 MK of the 171 Å band.
We conclude that oscillations of a single loop can not be detected
longer than 10-20 min in one single filter and appropriate light curve modeling
is necessary to disentangle the subsequent oscillation phases of multiple
Authors: Markus J. Aschwanden and Jaume Terradas
Publication Status: ApJ 686, L127-L130
Last Modified: 2008-12-02 09:30