Two-way coupled particle-in-cell and magnetohydrodynamic simulation of 2D fan-spine reconnection

¹ Rosseland Centre for Solar Physics, University of Oslo, P.O. Box 1029 Blindern, NO-0315 Oslo, Norway
² Institute of Theoretical Astrophysics, University of Oslo, P.O. Box 1029 Blindern, NO-0315 Oslo, Norway
³ Niels Bohr Institute, University of Copenhagen, Jagtvej 155A, 2200 Copenhagen, Denmark

^⋆ Corresponding author: michhaa@uio.no

Received: 4 June 2025
Accepted: 4 August 2025

Abstract

Context. Magnetic reconnection is a key mechanism for energy release in the solar atmosphere, but its kinetic-scale microphysics remains difficult to model in large-scale solar geometries.

Aims. We investigate whether fully kinetic particle-in-cell (PIC) simulations can be stably and meaningfully embedded within global magnetohydrodynamic (MHD) models of the solar corona using a realistic fan-spine magnetic configuration.

Methods. We employed a two-way coupled PIC-MHD scheme implemented in the DISPATCH code framework. The PIC solver is embedded within a reconnecting current sheet in a solar-like topology. A physical adjustment of constants is used to bridge kinetic and fluid scales while maintaining self-consistent plasma ordering.

Results. The system evolves stably over more than 45 000 ion plasma periods, exhibiting clear kinetic signatures such as Hall-driven quadrupolar magnetic fields, a reconnection geometry reminiscent of the Petschek configuration, and supra-thermal particle populations. The reconnection rate in the PIC region remains steady and physically consistent, while coupling artefacts are effectively suppressed by fade-in/fade-out boundary weighting.

Conclusions. Our results demonstrate that fully kinetic reconnection can be embedded in global solar MHD models with physical fidelity and computational efficiency. This hybrid approach offers a practical pathway to multi-scale kinetic modelling in realistic astrophysical environments.