On the relationship between expansion angle of Earth-directed CMES and soft X-ray emission from their related flare

Abstract

In space weather, to study the impact of Earth-directed coronal mass ejections (CME) in our terrestrial environment, one of the most important parameters is the propagation speed of these disturbances. We present an improvement of the 3D CME Geometrical Propagation-Expansion Description (3D-CGPED) model developed in previous work to increase the sample that we can use in CME arrival time predictions. This 3D model estimates the arrival time of Earth-directed CMEs at Earth by including a 3D geometry for the CME propagation and expansion in interplanetary space. Since the 3D-CGPED model computes the expansion of the CME based on the radial distance of the CME front, only travel times for CMEs with well-defined shapes seen by coronographs can be estimated. In the present work, we found an empirical relationship between the expansion angle of CMEs with well-defined shapes and the start-to-peak SXR fluence of their associated flares. We applied this relationship in the 3D-CGPED model to obtain the expansion angle for 8 CMEs with an irregular shape. We found similar window errors in arrival time predictions compared to the previous work. This result allows us to complement the 3D-CGPED model to include not only regular shapes but also irregular ones for CMEs observed by coronographs in future works.