Thin coronal jets and plasmoid-mediated reconnection

Insights from Solar Orbiter observations and Bifrost simulations

¹ Instituto de Astrofísica de Canarias, E-38205 La Laguna, Tenerife, Spain
² Universidad de La Laguna, Dept. Astrofísica, E-38206 La Laguna, Tenerife, Spain
³ Rosseland Centre for Solar Physics, University of Oslo, PO Box 1029 Blindern, 0315 Oslo, Norway
⁴ Institute of Theoretical Astrophysics, University of Oslo, PO Box 1029 Blindern, 0315 Oslo, Norway
⁵ Department of Physics and Astronomy, George Mason University, Fairfax VA 22030, USA
⁶ Heliophysics Science Division, NASA Goddard Space Flight Center, Greenbelt MD 20771, USA
⁷ Solar-Terrestrial Centre of Excellence–SIDC, Royal Observatory of Belgium, Ringlaan -3- Av. Circulaire, 1180 Brussels, Belgium
⁸ Centre for mathematical Plasma Astrophysics, Department of Mathematics, KU Leuven, Celestijnenlaan 200B, 3001 Leuven, Belgium

^⋆ Corresponding author: dnobrega@iac.es

Received: 30 April 2025
Accepted: 18 August 2025

Abstract

Context. Coronal jets are ubiquitous, collimated million-degree ejections that contribute to the energy and mass supply of the upper solar atmosphere and the solar wind. Solar Orbiter observations provide an unprecedented opportunity to study fine-scale jets from a unique vantage point close to the Sun.

Aims. We aim to uncover thin jets originating from coronal bright points (CBPs) and investigate observable features of plasmoid-mediated reconnection.

Methods. We analyzed eleven datasets from the High Resolution Imager 174 Å of the Extreme Ultraviolet Imager (HRI_EUV) on board Solar Orbiter, focusing on narrow jets from CBPs and signatures of magnetic reconnection within current sheets and outflow regions. To aid in the interpretation, we compared the observations with radiative-magnetohydrodynamic simulations of a CBP conducted with the Bifrost code.

Results. We identified thin coronal jets originating from CBPs with widths ranging from 253 km to 706 km. These are scales that could not be resolved with previous EUV imaging instruments. Remarkably, these jets are 30−85% brighter than their surroundings and can extend up to 22 Mm, while maintaining their narrow form. For one of the datasets, we directly identified plasmoid-mediated reconnection through the development within the current sheet of a small-scale plasmoid that reaches a length of 332 km and propagates at 40 km s⁻¹. For another dataset, we inferred indirect traces of plasmoid-mediated reconnection through the intermittent boomerang-like pattern that appears in the outflow region. The simulation self-consistently produces a current sheet and small-scale plasmoids similar to those observed, whose synthetic HRI_EUV emission reproduces both direct imprints within the current sheet and intermittent patterns in the outflow region associated with their ejection.

Conclusions. Our findings highlight Solar Orbiter’s unique capability to capture narrow jets and sub-megameter-scale plasmoid-mediated reconnection signatures in the corona. These results motivate future statistical studies aimed at assessing the role of such fine-scale phenomena in coronal dynamics and solar wind formation.