Optimal stereoscopic angle for 3D reconstruction of synthetic small-scale coronal transients using the CORAR technique

Abstract

Context.In previous studies, we applied the CORrelation-Aided Reconstruction (CORAR) technique to reconstruct three-dimensional (3D) structures of transients in the field of view (FOV) of Heliospheric Imager-1 (HI-1) on board the spacecraft STEREO-A/B. The reconstruction quality depends on the stereoscopic angle (θSun), that is, the angle between the lines connecting the Sun and two spacecraft.Aims.To apply the CORAR technique on images from the coronagraphs COR-2 on board STEREO, the impact ofθSunon the reconstruction of coronal transients should be explored, and the optimalθSunfor reconstruction should be found.Methods.We apply the CORAR method on synthetic COR-2 images containing the small-scale transient, namely the blob, in the case of variousθSun. Based on a comparison of the synthetic blob and the corresponding reconstructed structure in location and 3D shape, we assess its level of reconstruction quality. According to the reconstruction-quality levels of blobs in various positions with various attributes, we evaluate the overall performance of reconstruction in the COR-2 FOV to determine the optimalθSunfor reconstruction.Results.In the case ofθSun >  90°, we find that the range of suitableθSun, in which the small-scale transients in the COR-2 FOV typically have high reconstruction quality, is between 120° and 150°, and the optimalθSunfor reconstruction is close to 135°. In the case ofθSun <  90°, the global reconstruction performance is similar to that of (180° −θSun). We also discuss the spatial factors in determining the range of suitableθSun, and study the influence of blob properties on the reconstruction. Our work can serve as a foundation for the design of future missions containing coronagraphs from multiple perspectives, such as the newly proposed SOlar Ring mission (SOR).