The young associate researcher DUAN Yadan from Yunnan Observatories of Chinese Academy of Sciences and her co-authors have published a new research in The Astronomy & Astrophysics. Using unprecedentedly high-resolution observations from the Extreme Ultraviolet Imager (EUI) on board Solar Orbiter, they analyzed the dynamics of interchange reconnection in a small-scale fan-spine-like topology, revealing its cross-scale similarity with large-scale pseudostreamers.
Pseudostreamers are usually located more than 1.5 solar radii above the solar surface, have a ⋔-type structure, and are formed by multiple null points linked by separators. They are thought to play a significant role in the generation of slow solar wind. As one of the basic magnetic field skeletons, the separatrix curtain consists of open-flux fans of coronal nulls spreading out to solar wind. The fan-spine structure is defined by a dome-shaped fan separatrix surface, a magnetic null point positioned at its apex, and the inner and outer spines that pass through the null point. Recent observations revealed that the magnetic null-point position of fan-spine configurations is approximately 1−6 Mm above the solar surface.
This study used data from EUI to investigate the complex and variable reconnection dynamics of interchange reconnection within a small-scale fan-spine topology. Specifically, continuous evolution and a reversal of multiple current sheets were observed over time near the null point, which was likely modulated by emerging magnetic structures, such as mini-filaments and emerging arcades. In the outflow region of the third current sheet, a complex process of interchange magnetic reconnection continuously occurred near the magnetic null points, ultimately evolving into a curtain-like structure with a width of 1.7 Mm. Through wavelet and Fourier analysis, they found that both the curtain-like structure and the interchange reconnection occurring at the jet spire exhibited a quasi-periodicity of approximately 200 second.
This high-resolution study suggests that the occurrence of such complex and variable magnetic reconnection may be mediated by multiple magnetic null points. These results support the view of the cross-scale self-similarity of magnetic separatrix curtains and their associated interchange reconnection processes from the large-scale pseudostreamers down to tiny coronal jets.
This research was supported by the Strategic Priority Research Program of the Chinese Academy of Sciences, the National Science Foundation of China, and Yunnan Fundamental Research Projects.
Figure 1, schematic diagram of the evolution of the fan-spine magnetic field configuration and the evolution of multiple current sheets. (A-C) Snapshots from the EUI 174 Å show the first current sheet . (D-E) Snapshots from the EUI 174 Å images, along with time-distance diagrams (i1-i2) along the slits S1 and S2, collectively illustrate the transition from the second current sheet to the third current sheet. Image by DUAN.
Figure 2, schematic diagram of the dynamic evolution process of interchange reconnection in the outflow region of current sheets. (b)-(c) : The yellow arrows indicate three groups of magnetic loops, while the dashed black arrows show the sliding motion of these loops. (d) The pink arrows point to the reconnection locations between the three loops and the surrounding open fields. (f) The dashed yellow lines represent the open magnetic field lines after reconnection of the three groups. (g)-(i) illustrate the curtain-like features. Image by DUAN.
Contact:
DUAN Yadan
Yunnan Observatories, CAS
e-mail:duanyadan@ynao.ac.cn
