Relation between the 3D-geometry of the coronal wave and associated CME during the 26 April 2008 event

TL;DR

This study analyzes the 3D geometry and kinematics of a large-scale coronal wave associated with a 2008 flare-CME event, revealing asymmetric wave structure and CME-driven wave formation.

Contribution

It provides the first detailed 3D reconstruction of the coronal wave and its relation to the CME using stereoscopic observations, highlighting CME expansion as the wave driver.

Findings

Wave speed ~240 km/s, more pronounced eastward

CME speed ~750 km/s with non-radial eastward motion

Wave structure is asymmetric and inclined eastward

Abstract

We study the kinematical characteristics and 3D geometry of a large-scale coronal wave that occurred in association with the 26 April 2008 flare-CME event. The wave was observed with the EUVI instruments aboard both STEREO spacecraft (STEREO-A and STEREO-B) with a mean speed of ~240 km/s. The wave is more pronounced in the eastern propagation direction, and is thus, better observable in STEREO-B images. From STEREO-B observations we derive two separate initiation centers for the wave, and their locations fit with the coronal dimming regions. Assuming a simple geometry of the wave we reconstruct its 3D nature from combined STEREO-A and STEREO-B observations. We find that the wave structure is asymmetric with an inclination towards East. The associated CME has a deprojected speed of ~750+/-50 km/s, and shows a non-radial outward motion towards the East with respect to the underlying source region location. Applying the forward fitting model developed by Thernisien, Howard, and Vourlidas (2006), we derive the CME flux rope position on the solar surface to be close to the dimming regions. We conclude that the expanding flanks of the CME most likely drive and shape the coronal wave.