Numerical MHD Simulations of the 3D Morphology and Kinematics of the 2017 September 10 CME-driven Shock from the Sun to Earth

Abstract

A global, three-dimensional (3D) numerical simulation model has been employed to study the 3D morphology and kinematics of the large shock driven by the 2017 September 10 coronal mass ejection (CME). Based on actual solar observations, which include the photospheric magnetic field and the CME’s speed and source location, the simulation result is delicately tuned by matching with coronal polarized brightness observations and in situ solar-wind measurements at 1 au. The simulation reproduces well the shock’s shape and position in coronagraphic images. The shock’s physical parameters at 1 au are similar to those constrained from the observations, with the simulated transit time being nearly the same as the observed one. The simulation reveals that the shock around the backward direction keeps propagating away from the Sun, and despite its large extent, the shock cannot be seen as a spherical structure forming a 360° envelope around the Sun. Identified as a fast forward shock, the shock has a sharp velocity jump and a large density compression with a Mach number larger than one from the nose toward the lateral parts, consistent with a driven shock all across the front. Compared to the nose, the right flank of the shock has a weak compression ratio, but probably yields enhanced energetic particles for observers aligned with it. It follows that large CME-driven shocks have the potential to accelerate energetic particles over a wide longitudinal separation and are likely responsible for the production of these particles in the inner heliosphere.