Quasi-periodic fast-propagating (QFP) waves and extreme-ultraviolet (EUV) waves are two common waves in solar atmosphere. The origins of these fluctuations have been debated over the past few decades. Researchers suggested that they could be triggered by either a flare pulse or a coronal mass ejection (CME).

EUV waves are now thought to be caused by CMEs, and the origin of QFP waves is thought to be caused by flare pressure pulses. However, MIAO Yuhu's group from the Yunnan observatories of Chinese Academy Sciences discovered a quite different and interesting phenomenon.

In the 2011 March 10 solar activity eruption event (flare/CME), a QFP wave and a EUV wave were generated simultaneously. The first wavefront of the QFP wave train was the same as the wavefront of EUV wave. The study was published in The Astrophysical Journal Letters.

This event provided a good opportunity to study the trigger mechanism of the QFP wave and the EUV wave in depth. Since the front of QFP wave and EUV wave are the same wave train, STEREO satellite also confirmed the corresponding CME. Researchers believed that QFP waves can be excited by CMEs.

During the eruption, the initial broadband pulse can be dispersed and evolve into multiple wave train of the QFP.

The results showed that the shock wave, which is piston-driven by broadband pulse, can further evolve into QFP wave along the funnel-like coronal loops. In this event, both flare and CME were observed.

The study on this event is that CME eruption caused it. However, researchers need to study more cases and prove which of the two (flare/CME) is the real trigger mechanism.