The Inconvenient Truth About Coronal Dimmings

Abstract

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.

4 pages, 3 figures, submitted to ApJ - rerouted to ApJL

References in corpus (5)

• Self-consistent Coronal Heating and Solar Wind Acceleration from Anisotropic Magnetohydrodynamic Turbulence
• Alfven Waves and Turbulence in the Solar Atmosphere and Solar Wind
• The Post-Eruptive Evolution of a Coronal Dimming
• Reappraising Transition Region Line Widths in light of Recent Alfvén Wave Discoveries
• Simple Magnetic Flux Balance as an Indicator of Neon VIII Doppler Velocity Partitioning in an Equatorial Coronal Hole

Cited by in corpus (10)

• What can we learn about solar coronal mass ejections, coronal dimmings, and Extreme-Ultraviolet jets through spectroscopic observations?
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• Upflows in the upper solar atmosphere
• Evidence of Explosive Evaporation in a Microflare Observed by Hinode/EIS
• Plasma diagnostics of coronal dimming events
• Spectroscopic Analysis of an EIT Wave/Dimming Observed by Hinode/EIS
• The Spectroscopic Footprint of the Fast Solar Wind
• Spectroscopic analysis of interaction between an EIT wave and a coronal upflow region
• The Impact of New EUV Diagnostics on CME-Related Kinematics
• On the nature of spectral line broadening in solar coronal dimmings