Coronal "Wave": Magnetic Footprint of a Coronal Mass Ejection?

Abstract

We investigate the properties of two "classical" EUV Imaging Telescope (EIT) coronal waves. The two source regions of the associated coronal mass ejections (CMEs) possess opposite helicities, and the coronal waves display rotations in opposite senses. We observe deep core dimmings near the flare site and also widespread diffuse dimming, accompanying the expansion of the EIT wave. We also report a new property of these EIT waves, namely, that they display dual brightenings: persistent ones at the outermost edge of the core dimming regions and simultaneously diffuse brightenings constituting the leading edge of the coronal wave, surrounding the expanding diffuse dimmings. We show that such behavior is consistent with a diffuse EIT wave being the magnetic footprint of a CME. We propose a new mechanism where driven magnetic reconnections between the skirt of the expanding CME magnetic field and quiet-Sun magnetic loops generate the observed bright diffuse front. The dual brightenings and the widespread diffuse dimming are identified as innate characteristics of this process.

Large-scale Globally Propagating Coronal Waves

“…In 3D MHD simulations, they found that an electric current shell is formed around an erupting flux rope by return currents (see Figure 44). The shell rotates with the erupting flux rope, which is consistent with the rotation observed in some coronal EUV waves (Podladchikova and Berghmans, 2005;Attrill et al, 2007). A line-of-sight integration of the current shell results in an elliptical pattern that matches observed EUV wavefronts, and both bright and dark patches in two EIT waves could be reproduced quite well.…”

“…This strongly suggests that they correspond to the footpoints of an erupting flux rope that forms the core of a CME (e.g., Sterling and Hudson, 1997;Webb et al, 2000;Mandrini et al, 2005). In addition to these core dimmings, sometimes more widespread and shallow secondary dimmings are observed to trail behind an expanding EUV wavefront (e.g., Delannée and Aulanier, 1999;Wills-Davey and Thompson, 1999;Thompson et al, 2000b;Attrill et al, 2007;Muhr et al, 2011). The interpretation of these features is less clear-cut as in the case of core dimmings.…”

The link between CME-associated dimmings and interplanetary magnetic clouds

“…However, in the common studied case, the 28 October 2003 X17 flare and CME, we have shown that the observed extended dimmings are secondary. The formation of these secondary dimmings can be explained via a stepping reconnection process, similar to the mechanism proposed by Attrill et al (2007) for the bright front and diffuse leading edge of coronal waves. Although magnetic reconnection conserves magnetic flux, one cannot be sure how much of the magnetic flux in the secondary dimmings became part of the CME; therefore, these secondary dimming areas do not provide a proper proxy for magnetic flux measurements to be compared with interplanetary data.…”

Peculiar Stationary Euv Wave Fronts in the Eruption on 2011 May 11

“…They called such brightenings "stationary brightenings." Later on, such stationary brightenings were confirmed in several observational studies (Delannée 2000;Attrill et al 2007;Delannée et al 2007;Chandra et al 2009). Such a stationary front located at a magnetic separatrix, or a QSL in more general cases, was reproduced in numerical simulations, and can be explained by field-line stretching model (Chen et al 2005(Chen et al , 2006.…”