Evolution of a magnetohydrodynamic coronal shock

We present results from a study of the CME event that occurred in May 1997 using a data-driven three-dimensional (3-D), time-dependent, magnetohydrogynamic (MHD) numerical simulation model [1]. We focus on the initiation and evolution of the coronal mass ejection (CME) and its driven shock in the corona. The model takes the line-of-sight magnetic field at the photosphere as input to build the background corona and solar wind. A pressure pulse is applied to the simulation domain at the observed flare site to initiate a CME. A wave tracing method [2] is used to determine and trace the shock. It is found that the CME-driven shock starts forming at ∼1.5 solar radii (Rs) from the center of the Sun. The strength of the shock (Mach no. of fast shock) is found to increase with increasing heights (between 1.5 and 3.2 Rs). The increase in the shock strength is due to a decrease in the fast wave speed. In contrast, the density compression ratio of the shock is found to decrease as the shock propagates away from the Sun.