761 research outputs found
The Inconvenient Truth About Coronal Dimmings
We investigate the occurrence of a CME-driven coronal dimming using unique
high resolution spectral images of the corona from the Hinode spacecraft. Over
the course of the dimming event we observe the dynamic increase of non-thermal
line broadening in the 195.12Angstrom emission line of Fe XII as the corona
opens. As the corona begins to close, refill and brighten, we see a reduction
of the non-thermal broadening towards the pre-eruption level. We propose that
the dynamic evolution of non-thermal broadening is the result of the growth of
Alfven wave amplitudes in the magnetically open rarefied dimming region,
compared to the dense closed corona prior to the CME. We suggest, based on this
proposition, that, as open magnetic regions, coronal dimmings must act just as
coronal holes and be sources of the fast solar wind, but only temporarily.
Further, we propose that such a rapid transition in the thermodynamics of the
corona to a solar wind state may have an impulsive effect on the CME that
initiates the observed dimming. This last point, if correct, poses a
significant physical challenge to the sophistication of CME modeling and
capturing the essence of the source region thermodynamics necessary to
correctly ascertain CME propagation speeds, etc.Comment: 4 pages, 3 figures, submitted to ApJ - rerouted to ApJ
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