From incoherent field to coherent reconnection: understanding convection-driven coronal heating in the quiet Sun

Abstract: Magnetic reconnection in the quiet Sun is a phenomenon that is consistently observed, and it has recently become feasible to simulate via 3D numerical models of realistically stratified and convection-driven reconnection. We aim to illustrate ways by which quiet Sun fields may contribute to solar atmospheric heating via magnetic reconnection that is driven by convective motion. We also aim to compare our stratified model to earlier idealized coronal models in terms of reconnection drivers and topological conditions. We analyzed a simulation of the quiet Sun in which a complex coronal magnetic field is self-consistently driven by the underlying convection. We employed a selection of Lagrangian markers to trace the spatiotemporal behavior of specific magnetic features that are relevant to magnetic reconnection and atmospheric heating. A large-scale reconnection-driven heating event occurs in the simulated corona, in a flattened X-shaped feature characterized by a weak field and high current. Relevant features include a smooth overlying horizontal field, an arcade, and a horizontal flux rope which eventually reconnect with the overlying field, raising coronal plasma temperatures up to 1.47 MK. We find that our results are in good agreement with idealized coronal flare models, which demonstrates that the same physical concepts are valid. We also find that the reconnecting flux rope and arcade are neither formed by any obvious coherent flux emergence, nor by any ordered photospheric motion or flux cancellation. Instead, they seem to develop merely from the self-consistent convective driving of pre-existing tangled field lines. This gradual ordering suggests an inverse cascade of magnetic helicity via smaller reconnection events, located at or above photospheric flux concentrations. We suggest that this case is representative of heating events that may be ubiquitous in the real quiet Sun.