Solar jets are straight or bi-directional plasma flows, and they are ubiquitous in the solar atmosphere. Studying of solar jets are very important for understanding the enigmatic problems of coronal heating and the acceleration of solar wind. However, knowledge on the formation of solar jets is still scarce.

Based on high resolution multi-wavelength and stereoscopic observations taken by the Solar Dynamic Observatory (SDO) and the Solar Terrestrial Relations Observatory (STEREO), a solar group led by Dr. SHEN Yuandeng from Yunnan Observatories of Chinese Academy of Sciences, recently published their new finding in The Astrophysical Journal. They found that both straight and two-sided-loop jets are evolved from the eruption of mini-filaments located at the jet base, and experience two times magnetic reconnection process. These findings are new to previous understanding of the formation of solar jets.

According to Dr. SHEN’s explanation, a jet often started from the eruption of a mini-filament due to magnetic cancellation or some instabilities, the confining magnetic fields first reconnect with the ambient open or horizontal field lines, then, due to the rising of the filament, magnetic reconnection will occur underneath the filament resembling the eruption of large filaments (see Figure 1).

The basic formation mechanisms for the two kind of solar jets are similar, both of them include the eruption of a mini-filament and undergo two times of magnetic reconnection processes. However, due to different magnetic topologies, they will result in different outcomes. For a straight jet moving along open magnetic field lines, it often results in simultaneous jet-like and bubble-like coronal mass ejections; For a two-sided-loop jet along horizontal and closed loop, it can not cause coronal mass ejections in the outer corona.

"These findings not only advanced our understanding of the formation mechanism of solar jets, but also indicated the similarity of small- and large-scale solar eruptions”, said SHEN.

 Figure 1. The formation mechanism of the two types of solar jets. The top row is for straight jets, while the bottom row is for two-sided-loop jets. The red dashed lines indicate the reconnection positions, while the orange circle represents the mini-filament. The black and blue lines represent the magnetic field lines before and after the magnetic reconnections. Symbols ‘+’ and ‘-’ indicate the positive and negative magnetic polarities. (Image by SHEN Yuandeng)

Contact:

SHEN Yuandeng,Yunnan Observatories,CAS

ydshen@ynao.ac.cn