Dependence of the intensity of the nonwave component of EUV waves on coronal magnetic field configuration

TL;DR

This study investigates how the magnetic field configuration in the solar corona influences the formation and anisotropic intensity distribution of the slower nonwave component of EUV waves, combining observations and MHD simulations.

Contribution

It reveals that backward-inclined magnetic field lines promote the formation of the nonwave EUV component, providing new insights into the magnetic conditions affecting EUV wave structures.

Findings

Slower nonwave EUV component shows strong anisotropy.

Backward-inclined magnetic fields enhance the nonwave component.

Forward-inclined fields weaken the nonwave EUV features.

Abstract

Context. Mounting evidence has shown that EUV waves consist of a fast-mode magnetohydrodynamic (MHD) wave (or shock wave) followed by a slower nonwave component, as predicted by the magnetic fieldline stretching model. However, not all observed events display both wavefronts, particularly the slower nonwave component. Even in case that the slower nonwave component is present, the intensity distribution often exhibits strong anisotropy. Aims. This study is intended to unveil the formation condition of the slower nonwave component of EUV waves. Methods. 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. Results. Two types of EUV waves are identified, and the slower nonwave component exhibits strong anisotropy. By reconstructing 3D coronal magnetic fields, we found that the slower nonwave component of EUV waves is more pronounced in the regions where magnetic fields are backward-inclined, which is further reproduced by our MHD simulations. Conclusions. The anisotropy of the slower nonwave 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 are.