Observations of a Flare-ignited broad Quasi-periodic Fast-propagating wave train

TL;DR

This paper reports the observation of a broad, quasi-periodic fast wave train during a solar flare, revealing wave refraction, interference effects, and a weak shock driven by flare energy release, using high-resolution multi-angle EUV imaging.

Contribution

It presents the first detailed observation of a broad QFP wave train with multiple wavefronts and refraction effects passing through a coronal hole, highlighting wave interactions and shock characteristics.

Findings

Wave train transmitted through a coronal hole at 840 km/s.

Wavefronts exhibited refraction and collision, causing intensity enhancement.

Wave train identified as a weak shock with a 90-second period.

Abstract

Large-scale Extreme-ultraviolet (EUV) waves are frequently observed as an accompanying phenomenon of flares and coronal mass ejections (CMEs). Previous studies mainly focus on EUV waves with single wavefronts that are generally thought to be driven by the lateral expansion of CMEs. Using high spatio-temporal resolution multi-angle imaging observations taken by the Solar Dynamic Observatory and the Solar Terrestrial Relations Observatory, we present the observation of a broad quasi-periodic fast propagating (QFP) wave train composed of multiple wavefronts along the solar surface during the rising phase of a GOES M3.5 flare on 2011 February 24. The wave train transmitted through a lunate coronal hole (CH) with a speed of 840 +/-67 km/s, and the wavefronts showed an intriguing refraction effect when they passed through the boundaries of the CH. Due to the lunate shape of the CH, the transmitted wavefronts from the north and south arms of the CH started to approach each other and finally collided, leading to the significant intensity enhancement at the collision site. This enhancement might hint the occurrence of interference between the two transmitted wave trains. The estimated magnetosonic Mach number of the wave train is about 1.13, which indicates that the observed wave train was a weak shock. Period analysis reveals that the period of wave train was $\sim$90 seconds, in good agreement with that of the accompanying flare. Based on our analysis results, we conclude that the broad QFP wave train was a large-amplitude fast-mode magnetosonic wave or a weak shock driven by some non-linear energy release processes in the accompanying flare.