Work

Qorona: Open, Model-agnostic Line-of-sight Rendering of the Perpendicular Squashing Factor for Eclipse-like Coronal Imaging

Year: 2026

Type: article

Abstract: The fine structure of the white-light corona reflects the coronal magnetic topology, and the quasi-separatrix layers (QSLs), where the connectivity changes sharply and reconnection is expected to shape the density, are candidates for organizing it. In a coronal magnetohydrodynamic (MHD) model, the QSLs are located by the squashing factor Q , and integrating log 10 Q along the line-of-sight gives an eclipse-like image, a model-derived proxy for this structure, but no open-source tool dedicated to producing such images was previously available. To fill this gap, we present Qorona (a contraction of Q and corona; https://github.com/RayanDhib/Qorona ), an open-source Python package specifically designed to perform this rendering for any global coronal MHD solution using the perpendicular squashing factor Q ⊥ , the variant of Q that remains robust where field lines graze a boundary. Qorona is model-agnostic (a new model or file format requires only a reader) and fast: a field-line painting algorithm exploits the constancy of Q ⊥ along field lines to decouple volume resolution from tracing cost, and parallel CPU and GPU back ends build the volume in minutes. Because the volume is viewpoint-independent, a single build serves any number of cameras and a range of products beyond the eclipse image: polarity-colored and near-limb renders, a field-line view, and a synoptic signed- log 10 Q ⊥ map. The field-line tracer and Q ⊥ engine match the closed-form Q ⊥ of an analytic dipole to 10 −9 . We demonstrate the pipeline on a COCONUT coronal MHD simulation of the 2024 April 8 total solar eclipse: the three principal streamers of the synthetic Q ⊥ image lie within 7° in position angle of those observed.

Source: The Astrophysical Journal

DOI: 10.3847/1538-4357/aea841