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

Abstract

Although magnetic reconnection in coronal current sheets (CSs) is a fundamental energy release mechanism in the solar corona, the role of guide-fields in governing its formation and self-consistent evolution is not fully understood. Through 2.5D resistive magnetohydrodynamic (MHD) simulations, we investigate how guide-fields affect the formation and evolution of a localized reconnecting coronal CS. Strong guide-fields prevent oppositely directed field lines from approaching sufficiently to form a CS, delaying and suppressing its subsequent evolution. The reconnection rate exhibits a rising phase resembling a power-law, with exponent $δ_1$ decreasing with rising guide-fields, indicating slower temporal growth of the reconnection rate. The aspect ratio of the CS follows a similar power-law trend with the exponent $α_1$ decreasing with rising guide-fields. A subsequent slower growth phase of the reconnection rate shows a power-law exponent $δ_2$ that increases with rising guide-fields, as does the corresponding aspect-ratio exponent $α_2$. As the CS evolves, the latter phase is achieved due to a sharp decremental transition of the guide-field within the CS 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 the maximum temperature and the outflow velocities also decrease with rising guide-fields demonstrating that stronger guide-fields suppress the growth of these indicators also. This study suggests that a self-consistently formed CS displays phases of efficient and inefficient quenching of the reconnection mechanism, promoted by non-zero guide-fields. We also quantify this behavior for indicators of the reconnection process and discuss their applicability to observations of apparent CSs and probing background coronal conditions.