STEREO/SECCHI Observations on 8 December 2007: Evidence Against the Wave Hypothesis of the EIT Wave Origin
Abstract
The physical nature of EIT waves, large-scale bright fronts propagating in the solar corona, remains a subject of a continuing debate. Two main ways of interpreting this phenomenon have been suggested. One of them describes an EIT wave as a fast mode magnetosonic wave freely propagating in the corona. The other interpretation does not consider an EIT wave a true magnetohydrodynamic wave but instead invokes several possibilities linked to the magnetic field restructuring during the coronal mass ejection (CME) evolution in the low corona. We investigate an EIT wave observed by the SECCHI/EUVI telescopes onboard the STEREO spacecraft on 8 December 2007. The wave front had a nearly symmetric shape and exhibited a peculiar velocity profile measured by two independent methods. After an initial short propagation at a speed of around 100 km s−1, the wave was moving at a very low velocity (around 20 - 40 km s−1) for about 30 minutes, and then was reaccelerated up to speeds of around 200 km s−1. It is difficult to envisage such a velocity change for a freely propagating coronal wave. However, such a behavior is possible, for example, for erupting prominences. We conclude that this event provides observational evidence that even EIT waves with a symmetric front can be produced by a magnetic field restructuring during the CME eruption.
- Publication:
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Solar Physics
- Pub Date:
- October 2009
- DOI:
- 10.1007/s11207-009-9375-0
- Bibcode:
- 2009SoPh..259...73Z
- Keywords:
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- Coronal mass ejections;
- low coronal signatures;
- initiation and propagation