Journal Article

The Quasi-radial Field-line Tracing (QRaFT): An Adaptive Segmentation of the Open-flux Solar Corona

Rura, Christopher E, Arge, Charles Nickolos, Uritsky, Vadim M, Alzate, Nathalia, Jones, Shaela I, Downs, Cooper

2025

Overview

Optical observations of the solar corona provide key information on its magnetic geometry. The large-scale open field of the corona plays an important role in shaping the ambient solar wind and constraining the propagation dynamics of the embedded structures, such as interplanetary coronal mass ejections. Rigorous analysis of the open-flux coronal regions based on coronagraph images can be quite challenging because of the depleted plasma density, resulting in low signal-to-noise ratios. In this paper, we present an in-depth description of a new image segmentation methodology, the Quasi-Radial Field-line Tracing (QRaFT), enabling the detection of optical coronal features indicating the orientation of the steady-state open magnetic field. The methodology is tested using synthetic coronagraph images generated by a three-dimensional magnetohydrodynamic model. The results of the numerical tests indicate that the extracted optical features are aligned within ∼4°–7° with the local magnetic field in the underlying numerical solution. We also demonstrate the performance of the method on real-life coronal images obtained from a space-borne coronagraph and a ground-based camera. We argue that QRaFT outputs contain valuable empirical information about the global steady-state morphology of the corona, which could help improve the accuracy of coronal and solar wind models and space weather forecasts.

• Publisher: IOP Publishing
• Subject: Corona / Coronagraphs / Coronal mass ejection / Embedded structures / Image segmentation / Magnetic fields / Optical observations / Plasma density / Solar corona / Solar wind / Solar wind models / Space weather / Steady state / Tracing / Weather forecasting / Wind models