Dependence of the intensity of the non-wave component of extreme UV waves on the coronal magnetic field configuration

¹ Key Laboratory of Modern Astronomy and Astrophysics, School of Astronomy and Space Science, Nanjing University, Nanjing 210023, PR China
² State Key Laboratory of Lunar and Planetary Sciences, Macau University of Science and Technology, Macau 999078, PR China

^⋆ Corresponding author: chenpf@nju.edu.cn

Received: 4 March 2025
Accepted: 13 May 2025

Abstract

Mounting evidence has shown that extreme-ultraviolet (EUV) waves consist of a fast-mode magnetohydrodynamic (MHD) wave (or shock wave) followed by a slower non-wave component, as predicted by the magnetic field line stretching model. However, not all observed events display both wave fronts, particularly the slower non-wave component. Even when the slower non-wave component is present, the intensity distribution often exhibits strong anisotropy. This study is intended to unveil the formation condition of the slower non-wave component of EUV waves. We analyzed the EUV wave event on 8 March 2019 and compared the EUV wave intensity map with the extrapolation coronal potential magnetic field. Data-inspired MHD simulation was also performed. Two types of EUV waves are identified, and the slower non-wave component exhibits strong anisotropy. By reconstructing 3D coronal magnetic fields, we find that the slower non-wave component of EUV waves is more pronounced in regions where magnetic fields are backward-inclined, which is further reproduced by our MHD simulations. The anisotropy of the slower non-wave component of EUV waves is strongly related to the magnetic configuration, with backward-inclined field lines favoring their appearance. The more the field lines are forward-inclined, the weaker such wavelike fronts become.