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 ${\delta }_1$ 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 ${\alpha }_1$ decreasing with rising guide-fields. A subsequent slower growth phase of the reconnection rate shows a power-law exponent ${\delta }_2$ that increases with rising guide-fields, as does the corresponding aspect-ratio exponent ${\alpha }_2$. 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.

arXiv comment19 pages, 15 figures, Accepted for publication in Astronomy and Astrophysics