Work

Dynamical and thermal evolution of localized reconnecting current sheets under varying guide fields in the solar corona

Year: 2026

Type: article

Abstract: Although magnetic reconnection in coronal current sheets is a fundamental energy release mechanism in the solar corona, the role of the guide field in governing its formation and self-consistent dynamical and thermal evolution is not fully understood. We investigate how varying the guide field strength affects the formation and evolution of a localized reconnecting coronal current sheet, as well as its thinning, reconnection rate, and plasma properties. We performed 2.5D resistive magnetohydrodynamic (MHD) simulations of the formation and subsequent reconnection of coronal current sheets across a diverse range of guide field strengths, tracking the temporal evolution of the reconnection rate, current-sheet geometry, temperature, and outflow velocities. A stronger guide field prevents oppositely directed field lines from approaching sufficiently to form the current sheet, delaying and suppressing its subsequent evolution. The reconnection rate (η J_ max ) exhibits a rising phase resembling a power law, with exponent δ_1 decreasing with increasing guide field, indicating slower temporal growth of the reconnection rate with increasing guide fields. The aspect ratio, which characterizes the thinning of the current sheet, follows a similar power-law trend with the exponent α_1 also decreasing with the strength of the guide field. A subsequent slower growth phase of η J_ max shows a power law exponent δ_2 that increases with guide field, as does the corresponding aspect-ratio exponent α_2. During the evolution of the current sheet, the latter phase is achieved due to the sharp decremental transition of the guide field within the current sheet after a time when the increasing inflows are inefficiently resisted by the guide field itself. In the reconnection regime during prior phases, the power law exponents of both the maximum temperature and the outflow velocities also decrease with an increasing guide field demonstrating that stronger guide fields suppress the growth of these observational signatures of reconnection. The present study suggests that in the presence of nonzero guide fields, a self-consistently formed current sheet displays phases of efficient and inefficient quenching of the reconnection mechanism, promoted by the aforementioned guide fields. With increasing guide field strengths, we further quantified this behavior for various indicators of the reconnection process. We also discuss the applicability of the obtained results to observations of apparent current sheets as well as probing background coronal conditions without any knowledge of guide field observations.

Source: Astronomy and Astrophysics

DOI: 10.1051/0004-6361/202660621