Scientists have found evidence that flares excite large-scale quasi-periodic coronal waves

Recently, the Coronal Observation and Site Selection Group of the Yunnan Astronomical Observatory of the Chinese Academy of Sciences has made new progress in the study of the origin of coronal waves. The study, done by PhD student Xinping Zhou, was published May 1 in The Astrophysical Journal Letter. The results provide reliable evidence for the first time that flares excite coronal waves, and the interference phenomenon of coronal waves is also reported for the first time.

The results show that coronal waves usually occur during the ACCELERATED PHASE OF CME, so coronal waves are often considered to be fast-mode magnetic acoustic waves with diffuse unidirectional wavefront driven by the expansion of CME flanks. Through a study of the February 24, 2011 event, Zhou Xinping found that there were multiple wavefronts in the corona wave, and that these wavefronts appeared at a time behind the accelerated phase of the CME. This contradicts the interpretation of the piston shock wave of the CME as a driver excitation, and it is difficult to explain multiple wavefronts in the event using a single CME burst. In addition, they found that the flare and the wave column had the same period, and the start time of the flare pulse phase was slightly earlier than the start time of the wave column by a few minutes. So they deduced that these wave columns should be excited by flares rather than driven by the flanks of the CME. At the same time, the study also observed for the first time a significant increase in the strength of the wavefront at the interference position due to the interference effect.

This study provides strong evidence for flare stimulation of large-scale coronal waves, and the observed interference effect enriches the performance characteristics of coronal waves, while providing observational evidence for the true wave nature of coronal waves.

The plot shows the evolutionary characteristics of multiple wavefronts. The green curve in the figure represents the contour of the coronal hole boundary, the red and blue arrows indicate multiple wavefront locations, and the white curve is the contour of the wavefront in the coronal hole area.

This work has been supported by the National Natural Science Foundation of China, the Basic Research Program of Yunnan Province, the National Key Research program and other projects. (Source: Yunnan Astronomical Observatory, Chinese Academy of Sciences)

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