Three-dimensional Reconstructions of Extreme-ultraviolet Wave Front Heights and Their Influence on Wave Kinematics

Abstract

Abstract EUV waves are large-scale disturbances in the solar corona initiated by coronal mass ejections. However, solar EUV images show only the wave front projections along the line of sight of the spacecraft. We perform 3D reconstructions of EUV wave front heights using multipoint observations from STEREO-A and STEREO-B, and we study their evolution to properly estimate the EUV wave kinematics. We develop two different methods to solve the matching problem of the EUV wave crest on pairs of STEREO-A/B images by combining epipolar geometry with the investigation of perturbation profiles. The proposed approaches are applicable at the early and maximum stage of the event when STEREO-A/B see different facets of the EUV wave, but also at the later stage when the wave front becomes diffusive and faint. The techniques developed are demonstrated on two events observed at different separations of the STEREO spacecraft (42° and 91°). For the 2007 December 7 event, we find that the emission of the EUV wave front mainly comes from a height range up to 90–104 Mm, decreasing later to 7–35 Mm. Including the varying height of the EUV wave front allows us to correct the wave kinematics for the projection effects, resulting in velocities in the range of 217–266 km s−1. For the 2009 February 13 event, the wave front height almost doubled from 54 to 93 Mm over 10 minutes, and the velocity derived is 205–208 km s−1. In the two events under study, the corrected speeds differ by up to 25% from the uncorrected ones, depending on the wave front height evolution.