Formation of Fan-spine Magnetic Topology through Flux Emergence and Subsequent Jet Production

Abstract

Fan-spine magnetic structure, as a fundamental three-dimensional topology in magnetic reconnection theory, plays a crucial role in producing solar jets. However, how fan-spine configurations form in the solar atmosphere remains elusive. Using the Chinese Hα Solar Explorer (CHASE) and the Solar Dynamics Observatory, we present a case study on the complete buildup of fan-spine topology driven by flux emergence and the subsequent jet production. Two fan-spine structures and the two associated null points are present. Variations in null-point heights and locations were tracked over time during flux emergence. The north fan-spine structure is found to be created through magnetic reconnection between the newly emerged flux and the background field. Gentle reconnection persistently occurs after formation of the north fan-spine structure, resulting in weak plasma outflows. Subsequently, as flux emergence and magnetic helicity injection continue, the formation and eruption of minifilaments after reconnection at the quasi-separatrix layer between the two nulls trigger three homologous jets. The CHASE observations reveal that the circular flare ribbon, inner bright patch, and remote brightening all exhibit redshifted signatures during these jet ejections. This work unveils the key role of flux emergence in the formation of fan-spine topology, and highlights the importance of minifilaments for subsequent jet production.

On the Determining Physical Factor of Jet-related Coronal Mass Ejections’ Morphology in the High Corona

“…When the filament lifts at 04:25 UT, an inner bright patch can be identified in Figure 2(b2). These characteristics suggest that the filament is situated within a fan-spine magnetic field configuration, as suggested by previous works (e.g., Shen et al 2019b;Yang et al 2020b;Zhou et al 2021a;Duan et al 2022Duan et al , 2024. The filament flux reconnects with and releases or a kink-like instability of the stressed internal closed field (e.g., Pariat et al 2009;Karpen et al 2017) and subsequently erupts, forming a jet along the magnetic field lines, as shown in the 304 and 131 Å sequence images in Figure 3.…”

“…Considering the three-dimensional (3D) scenario, with the aid of magnetic field extrapolation techniques and high-resolution observations, an increasing number of studies revealed that the 3D magnetic configuration of the coronal jets is a fan-spine structure (Shen 2021). This structure is composed of a null point, a dome-shaped fan, and the inner (outer) spines located inside (outside) the fan, which is typically accompanied by a circular flare ribbon and an inner bright patch (e.g., Masson et al 2009;Wang & Liu 2012;Li et al 2017Li et al , 2018Shen et al 2019b;Hou et al 2019;Lee et al 2020;Duan et al 2022Duan et al , 2024Huang et al 2024;Zhang 2024). In a high-resolution MHD simulation, Wyper et al (2017Wyper et al ( , 2018 showed a breakout model (Antiochos et al 1999) for coronal jets in a 3D fan-spine structure involving small filaments.…”