Can a Fast-mode EUV Wave Generate a Stationary Front?

TL;DR

This study demonstrates through MHD simulations that a fast-mode EUV wave can generate a stationary front when passing through a magnetic QSL, due to mode conversion near plasma beta ~ 1.

Contribution

It provides the first numerical evidence that fast-mode waves can produce stationary fronts via mode conversion at magnetic QSLs.

Findings

Stationary wave fronts can form from fast-mode waves passing through QSLs.

Mode conversion from fast to slow MHD waves occurs near plasma beta ~ 1.

Caution is needed in interpreting EUV wave observations regarding their nature.

Abstract

The discovery of stationary "EIT waves" about 16 years ago posed a big challenge to the then favorite fast-mode wave model for coronal "EIT waves". It encouraged the proposing of various non-wave models, and played an important role in approaching the recent converging viewpoint, {\it i.e.} there are two types of EUV waves. However, it was recently discovered that a stationary wave front can also be generated when a fast-mode wave passes through a magnetic quasi-separatrix layer (QSL). In this paper, we perform a magnetohydrodynamic (MHD) numerical simulation of the interaction between a fast-mode wave and a magnetic QSL, and a stationary wave front is reproduced. The analysis of the numerical results indicates that near the plasma beta $\sim 1$ layer in front of the magnetic QSL, part of the fast-mode wave is converted to a slow-mode MHD wave, which is then trapped inside the magnetic loops, forming a stationary wave front. Our research implies that we have to be cautious in identifying the nature of a wave since there may be mode conversion during the propagation of the waves driven by solar eruptions.