Treffer: Optimization of the FRi3D CME Model in EUHFORIA.

To study the evolution and propagation of Coronal Mass Ejections (CMEs), the advanced magnetized flux rope CME model, Flux Rope in 3D (FRi3D), has been integrated into the European Heliospheric Forecasting Information Asset (EUHFORIA). Recent updates have been addressing the computational efficiency and numerical stability issues of this CME model. In this work, the latest improvements to the FRi3D model are represented, including optimizations of the integral calculations in the ai.fri3d Python package, an updated CME leg disconnection method, and the introduction of a new datacube injection methodology for time‐efficient FRi3D simulations. Within the datacube injection method, the input values of FRi3D at the inner boundary of EUHFORIA are precomputed, eliminating the need to calculate the FRi3D CME model during the solar wind simulation with superimposed CMEs. The datacube injection method is tested by modeling the CME event of 12 July 2012, and by conducting ensemble runs for this event. The updates to the FRi3D Python package reduced the computation time to 55% $55\%$, and the datacube methodology achieved a computational time reduction of up to 95% $95\%$ compared to previous FRi3D versions. Numerical stability was significantly improved, and ensemble simulations demonstrated robust ensemble spreads for the thermodynamic and magnetic time profiles on Earth. These updates enhance the efficiency, stability, and accuracy of the FRi3D model, making it highly suitable for predicting both the CME arrival time, magnetic field strength, and velocity. As a result, the advancements contribute significantly to the future operational space weather forecasting capabilities of the FRi3D CME model. Plain Language Summary: Coronal Mass Ejections (CMEs) are solar eruptions that can significantly impact Earth. Space weather research relies on solar wind simulation frameworks like EUHFORIA to predict their arrival time and effects. The CME models within EUHFORIA are constantly improved, becoming more realistic over time. One of the newest and most advanced CME models in EUHFORIA, Flux Rope in 3D (FRi3D), provides a highly accurate 3D representation of a CME. However, this enhanced realism of the FRi3D model comes at a high computational cost. This paper presents significant improvements to the FRi3D model, aimed at overcoming previous computational challenges associated with this CME model. Firstly, the computation time has been significantly reduced by optimizing the integrals used to calculate the input values of FRi3D at the inner boundary of the simulation domain in EUHFORIA, approximately halving the required computation time. Secondly, an alternative injection technique, the datacube method, was implemented in EUHFORIA, which precomputes the 3D CME structure, eliminating redundant calculations during the simulation and reducing computational time by up to 95%. These advancements make the previously prohibitive FRi3D model a more efficient and reliable tool for future space weather forecasting. Key Points: Optimization of FRi3D input value calculations through integral simplification, leading to enhanced computational efficiencyImplementation of a datacube injection method, precomputing and storing input values of the FRi3D Coronal Mass Ejection model to avoid redundant calculationsThe datacube method reduces the computational cost of FRi3D in European Heliospheric Forecasting Information Asset by ∼ ${\sim} $95%, enhancing its suitability for operational forecasting [ABSTRACT FROM AUTHOR]

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