Solar flares and coronal mass ejections (CMEs) are the main manifestations of solar storms, which are considered to be caused by the impulsive release of non-potential energy through magnetic reconnection. These violently energetic releases will have a significant influence on the solar atmosphere, resulting in various solar phenomena and activities, including various types of magnetohydrodynamic (MHD) waves.

One of the hot topics in solar physics is the understanding of large-scale MHD waves in the corona. The properties of these large-scale MHD waves could be utilized to diagnose various important physical parameters in the corona (such as magnetic field).

In a recent study published in The Astrophysical Journal Letters, Dr. WANG Jincheng, Prof. YAN Xiaoli and other researchers from Yunnan Observatories, Chinese Academy of Sciences found that the excitation of two homologous quasi-periodic fast-mode propagating (QFP) wave trains are closely related to the outflow of the magnetic reconnection.

Coronal QFP wave trains are composed of multiple, coherent, arc-shaped wavefronts with the propagating speeds of ～500-2000 km/s. They can run ahead of or behind the CME bubble. So far, the excitation mechanism of these phenomena is still controversial. More observational clues are urged to figure out the exact excitation mechanism of QFPs.

Based on high spatial and temporal resolution Hα data from the New Vacuum Solar Telescope, and simultaneous observations from other ground-based and space-based telescopes, the researchers studied the characteristics of two homologous QFP wave trains on 2017 September 12. They also discussed and probed the generation mechanism of QFP wave trains.

The researchers found that the propagating speed of the first QFP wave train was calculated to be 815±58 km/s and the period was estimated as 59±2 seconds. For the second QFP wave train, its propagating speed could be derived as 753±45 km/s and it had two periods of 70±4 and 37±4 seconds. On the other hand, The QFP wave trains are closely associated with the perturbations of 94 and 335 Å intensity peaks in the flare kernel, strongly suggesting that they have a common exciting mechanism. Furthermore, the researchers identified that the emissions of the intensity peaks mainly originate from the one footpoint of flaring loops during the occurrences of QFP wave trains.

According to the observational features, the researchers concluded that the QFP wave trains are excited in the energy release process associated with magnetic reconnection, and are closely related to the outflow of the magnetic reconnection.

Contact:
WANG Jincheng,
Yunnan Observatories, CAS
Email: wangjincheng@ynao.ac.cn