Simulations of Coronal Mass Ejections on a Young Solar-type Star and Their Detectability Through Coronal Spectral Observations

Abstract

There is a growing interest in searching for coronal mass ejections (CMEs) in other stellar systems, because they are thought to be one of the important factors shaping planetary atmospheres. We investigated the possible spectral signatures related to stellar CMEs using magnetohydrodynamic (MHD) simulations and spectral synthesis techniques. Blue-wing enhancements of the synthetic coronal line profiles caused by the line-of-sight motion of plasma were observed during the simulated CME events. We included instrumental conditions in the spectral synthesis and tested the detectability of the asymmetries under different instrumental broadening conditions. The results show that blue-wing asymmetries are visible in some extreme-ultraviolet lines with spectral resolutions higher than around 2000, and the line-of-sight velocities of CMEs obtained from asymmetry analysis techniques are comparable to the CME velocities derived from three-dimensional model outputs. However, when the spectral resolution drops below 2000, the asymmetries in the blue wings become barely visible, but blueshifts in the line centroids with velocities around −100 to −200 km s ^−1 are observed. We suggest a method of using MHD simulations to synthesize line profiles and analyze their asymmetries that may help to guide future instrument design, in terms of detecting stellar CMEs through Doppler shifts or the asymmetries of coronal spectral lines.

Keywords

• Stellar coronal mass ejections
• Magnetohydrodynamical simulations
• Extreme ultraviolet astronomy