Modelling the total solar eclipse in 2024 with COCONUT

¹ Department of Mathematics/Centre for mathematical Plasma Astrophysics, KU Leuven Celestijnenlaan 200B 3001 Leuven, Belgium
² Institute of Physics, University of Maria Curie-Skłodowska ul. Radziszewskiego 10 20-031 Lublin, Poland

^★ Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 8 July 2025
Accepted: 30 October 2025

Abstract

Context. Coronal modelling is crucial for a better understanding of solar physics and heliophysics. Accurate plasma conditions at the outer boundary of a solar corona lead to more precise space weather predictions. Because the Sun is so very bright and we lack white-light (WL) observations of the solar atmosphere and low corona (1–1.5 R_⊙), total solar eclipses have become a standard approach for validating the coronal models. We validate the coronal model COCONUT by predicting the coronal configuration during the total solar eclipse on April 8, 2024.

Aims. We aim to predict the accurate configuration of the solar corona during the total solar eclipse on April 8, 2024. Additionally, we compare the predictive capabilities in the steady and dynamic driving of the boundary conditions in COCONUT. We used a full 3D magnetohydrodynamics (MHD) model to reconstruct the solar corona from the solar surface to 30 R_⊙.

Methods. We started by predicting the upcoming total solar eclipse on March 21. The predictions were conducted in three different regimes: quasi-steady driving of the inner boundary conditions (BCs) with a daily cadence, and dynamic driving of the inner BCs with daily and hourly cadences. The results from all the simulations were compared to the total solar eclipse images. Additionally, the synthetic WL images were generated from the Solar Terrestrial Relations Observatory Ahead (STEREO-A) field of view and compared to COR2 observed images. The normalised polarised brightness was compared in the COR2 and synthetic WL images.

Results. The predicted solar corona does not vary significantly in the first half of the prediction window because the observations of the magnetic field are not yet accurately updated on the solar surface corresponding to April 8. The magnetic field changes more significantly as the eclipse date approaches. The dynamic simulations yielded better results than the quasi-steady predictions. Driving the simulations at a higher cadence did not significantly improve the results because the magnetic field maps are highly processed. The west limb was better reconstructed in the simulations than the east limb.

Conclusions. We predicted the total solar eclipse coronal configuration 18 days before the total solar eclipse. We conclude that the dynamic simulations produced more accurate predictions. The availability of comprehensive observations is crucial because the emergence of the active region on the east limb made it difficult to accurately predict the east-limb coronal configuration because the input of the magnetic field data was incorrect. More detailed input BCs are necessary for reconstructing smaller-scale structures in the corona.