First observations of a dome-shaped large-scale coronal EUV wave

TL;DR

This paper reports the first observations of a dome-shaped large-scale EUV coronal wave, analyzing its structure, propagation, and evolution, and concludes it is consistent with a weakly shocked fast-mode MHD wave.

Contribution

It provides the first detailed observational evidence of a dome-shaped EUV wave and distinguishes it from CME structures, supporting the wave interpretation.

Findings

The wave dome has a velocity of ~650 km/s upward and ~280 km/s laterally.

The wave's amplitude decreases as r^{-2.5}, with a broadening width.

The observations are consistent with a spherical expansion of a weakly shocked fast-mode MHD wave.

Abstract

We present first observations of a dome-shaped large-scale EUV coronal wave, recorded by the EUVI instrument onboard STEREO-B on January 17, 2010. The main arguments that the observed structure is the wave dome (and not the CME) are: a) the spherical form and sharpness of the dome's outer edge and the erupting CME loops observed inside the dome; b) the low-coronal wave signatures above the limb perfectly connecting to the on-disk signatures of the wave; c) the lateral extent of the expanding dome which is much larger than that of the coronal dimming; d) the associated high-frequency type II burst indicating shock formation low in the corona. The velocity of the upward expansion of the wave dome ($v \sim 650$ km s$^{-1}$) is larger than that of the lateral expansion of the wave ($v \sim 280$ km s$^{-1}$), indicating that the upward dome expansion is driven all the time, and thus depends on the CME speed, whereas in the lateral direction it is freely propagating after the CME lateral expansion stops. We also examine the evolution of the perturbation characteristics: First the perturbation profile steepens and the amplitude increases. Thereafter, the amplitude decreases with r$^{-2.5 \pm 0.3}$, the width broadens, and the integral below the perturbation remains constant. Our findings are consistent with the spherical expansion and decay of a weakly shocked fast-mode MHD wave.