3D structures of the base of small-scale recurrent jets revealed by Solar Orbiter

¹ Max Planck Institute for Solar System Research, Göttingen D-37077, Germany

^⋆ Corresponding author: lixiaohong@mps.mpg.de

Received: 16 June 2025
Accepted: 6 September 2025

Abstract

Context. Solar jets, characterized by small-scale plasma ejections along open magnetic field lines or the legs of large-scale coronal loops, play a crucial role in the dynamics of the solar atmosphere. They are often associated with other solar active phenomena, including campfires, filament eruptions, coronal bright points, flares, and coronal mass ejections.

Aims. Although spectral and extreme-ultraviolet images have been widely used to analyze the formation and evolution of jets, the detailed 3D structure at the base of the jet has not been studied in detail, due to the limitations in the spatial resolution of observations.

Methods. Solar Orbiter enables us to investigate the structure of solar jets with much higher spatial and temporal resolutions and from a different angle than from Earth. By combining observations made by instruments on board Solar Orbiter with data from the Solar Dynamics Observatory, we analyzed recurrent solar jets originating in a mixed-polarity region near an active region. Additionally, we employed potential field and magneto-hydrostatic extrapolation techniques to determine the magnetic field topology associated with the jets.

Results. The jets display dynamic, multistrand outflows emanating from compact bright kernels above the magnetic inversion line, with apparent speeds exceeding 100 km s⁻¹. Magnetic field evolution reveals continuous flux cancellation at the jet footpoints. Throughout the sequence, base flows are confined within quasi-separatrix layers, with the highest velocities and temperatures located near coronal null points. Over four eruptions, the magnetic topology evolves from a simple fan–spine configuration with a single null to a more complex dome-shaped base containing multiple nulls with a separatrix curtain, accompanied by a morphological transition from a narrow, well-collimated spire to broader, fragmented outflows.

Conclusions. These results provide the first direct observational evidence that dynamic changes in null-point geometry modulate jet morphology and energetics via successive reconnection episodes.