Modelling of asymmetric nanojets in coronal loops

Pagano, P., Antolin, Patrick and Petralia, A. (2021) Modelling of asymmetric nanojets in coronal loops. Astronomy & Astrophysics, 656. A141. ISSN 0004-6361

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Context. Observations of reconnection jets in the solar corona are emerging as a possible diagnostic for studying highly elusive coronal heating. Such jets, and in particular those termed nanojets, can be observed in coronal loops and have been linked to nanoflares. However, while models successfully describe the bilateral post-reconnection magnetic slingshot effect that leads to the jets, observations reveal that nanojets are unidirectional or highly asymmetric, with only the jet travelling inward with respect to the coronal loop's curvature being clearly observed.
Aims. The aim of this work is to address the role of the curvature of the coronal loop in the generation and evolution of asymmetric reconnection jets. Methods. We first use a simplified analytical model in which we estimate the post-reconnection tension forces based on the local intersection angle between the pre-reconnection magnetic field lines and their post-reconnection retracting length towards new equilibria. Second, we use a simplified numerical magnetohydrodynamic (MHD) model to study how two opposite propagating jets evolve in curved magnetic field lines.
Results. Through our analytical model, we demonstrate that in the post-reconnection reorganised magnetic field, the inward directed magnetic tension is inherently stronger (by up to three orders of magnitude) than the outward directed one and that, with a large enough retracting length, a regime exists where the outward directed tension disappears, leading to no outward jet at large, observable scales. Our MHD numerical model provides support for these results, proving also that in the subsequent time evolution the inward jets are consistently more energetic. The degree of asymmetry is also found to increase for small-Angle reconnection and for more localised reconnection regions.
Conclusions. This work shows that the curvature of the coronal loops can play a major role in the asymmetry of the reconnection jets and that inward directed jets are more likely to occur and are more energetic than the corresponding outward directed ones.

Item Type: Article
Additional Information: Funding Information: P.A. acknowledges funding from STFC Ernest Rutherford Fellowship (No. ST/R004285/2). This work used the DiRAC@Durham facility managed by the Institute for Computational Cosmology on behalf of the STFC DiRAC HPC Facility ( The equipment was funded by BEIS capital funding via STFC capital grants ST/P002293/1, ST/R002371/1 and ST/S002502/1, Durham University and STFC operations grant ST/R000832/1. DiRAC is part of the National e-Infrastructure. PLUTO was developed at the Turin Astronomical Observatory in collaboration with the Department of Physics of the Turin University. A.P. acknowledges financial contribution from the agreement ASI-INAF n.2018-16-HH.0.
Uncontrolled Keywords: Sun: corona, Sun: magnetic fields, magnetohydrodynamics (MHD), Sun: atmosphere
Subjects: F300 Physics
F500 Astronomy
Department: Faculties > Engineering and Environment > Mathematics, Physics and Electrical Engineering
Depositing User: John Coen
Date Deposited: 14 Jan 2022 12:17
Last Modified: 14 Jan 2022 12:30

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