Magnetic Reconnection in a Compact Magnetic Dome: Chromospheric Emissions and High-velocity Plasma Flows

Abstract

Magnetic reconnection at small spatial scales is a fundamental driver of energy release and plasma dynamics in the lower solar atmosphere. We present observations of a brightening in an active region, captured in high-resolution data from the Daniel K. Inouye Solar Telescope (DKIST) using the Visible Broadband Imager (VBI) and the Visible Spectro-Polarimeter (ViSP). The event exhibits Ellerman bomb-like morphology in the H$\beta$ filter, associated with flux cancellation between a small negative polarity patch adjacent to opposite-polarity plage. Additionally, it displays enhanced emissions in Ca II K, hot elongated features containing Alfv\'enic plasma flows, and cooler blue-shifted structures. We employ multi-line, non-local thermodynamic equilibrium (non-LTE) inversions of the spectropolarimetric data to infer the stratification of the physical parameters of the atmosphere. Furthermore, we use the photospheric vector magnetogram inferred from the ViSP spectra as a boundary condition for nonlinear force-free field extrapolations, revealing the three-dimensional distribution of squashing factors. We find significant enhancements in temperature, velocity, and microturbulence confined to the upper photosphere and low chromosphere. Our findings provide observational evidence of low-altitude magnetic reconnection along quasi-separatrix layers in a compact fan-spine-type configuration, highlighting the complex interplay between magnetic topology, energy release, and plasma flows.