The Doctoral candidate, DUAN Yadan, from Yunnan Observatories of the Chinese Academy of Sciences and her co-authors reported an interesting study on the initiation of a solar jet. The authors found the homologous high-energy particles associated with the same flare, and used these observations to diagnose the jet magnetic reconnection process. The result was published in The Astrophysical Journal Letter recently.

Solar jets are frequently observed in a special fan-spine configuration and are closely associated with the null-point magnetic reconnection process. For some fan-spine systems whose outer spines extend into interplanetary space, they naturally provide an avenue for energetic electrons accelerated in the magnetic reconnection process to escape into interplanetary space and therefore lead to the formation of type III radio bursts in radio spectra. However, so far, the imaging signatures of accelerated electrons have not yet been detected in the closed outer spines.

They studied a solar jet that occurred in a fan-spine magnetic system hosted by a large-scale pseudostreamer. This unique coupled magnetic system provides clues to interpret the various physical phenomena they observed. Based on multi-wavelength observations, the whole physical process of the event interprets as follows:

A low-lying mini-filament below the fan structure first starts to rise slowly for some reason (for example, magnetic flux emergence or cancellations), which will squeeze the overlying magnetic fields and leads to the formation of a current sheet around the coronal null point. The magnetic reconnection within the current sheet not only removes the confining magnetic field of the mini-filament but also accelerates electrons.

Subsequently, the downward-accelerated electrons result in the formation of the inner bright patch and the circular flare ribbon, while those upward ones along the open field lines of the pseudostreamer and the closed field lines of the outer spine of the fan-spine system result in the formation of the observed type III radio burst and the on-disk fast-moving radio source, respectively. Due to the continuous reduction of the confinement magnetic field overlying the mini-filament, the slow-rising mini-filament eventually loses its equilibrium completely and therefore erupts violently to form an ejected jet.

In the process, they also observed a quasiperiodic fast-propagating wave train in front of the jet and captured a jet-like coronal mass ejections in the high corona.

This work reveals that the type III radio burst and the on-disk fast-moving radio source are homogenous electrons which are accelerated by the same physical process (i.e., the null-point reconnection) but propagated along different field system.

Contact:

SHEN Yuandeng, Yunnan Observatories, CAS

ydshen@ynao.ac.cn