Constraining the magnetic flux of the CME spheromak model in EUHFORIA with the magnetic helicity budget: Case study of 10 March 2022 CME

¹ Section of Astrogeophysics, Department of Physics University of Ioannina 45110, Greece
² Institute of Physics, University of M. Curie-Skłodowska Pl. M. Curie-Skłodowskiej 1 20-031 Lublin, Poland
³ Department of Physics, University of Helsinki Helsinki, Finland
⁴ Centre for Mathematical Plasma Astrophysics KU Leuven 3001 Leuven, Belgium
⁵ Royal Observatory of Belgium B-1180 Uccle, Belgium
⁶ Space Exploration Sector, Johns Hopkins Applied Physics Laboratory Laurel MD 20723, USA
⁷ Research Centre for Astronomy and Applied Mathematics, Academy of Athens 11527 Athens, Greece (on leave)

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Received: 18 June 2025
Accepted: 12 December 2025

Abstract

Aims. We propose a new method for constraining the magnetic flux of the spheromak coronal mass ejection (CME) in the European Heliospheric Forecasting Information Asset (EUHFORIA) by utilising the CME’s helicity content and comparing its efficiency with conventional methods. As a proof of concept, we analysed a CME observed on 10 March 2022 from the NOAA active region (AR) 12962. The simulation results were compared with in situ magnetic field and plasma measurements from Solar Orbiter (SolO) at 0.43 AU and WIND at 0.99 AU to assess the method’s reliability and parameter dependencies.

Methods. The CME magnetic helicity was related to the spheromak axial field strength (B_spheromak). From this result, the toroidal magnetic flux was derived using the CME geometry. Additionally, we assessed the sensitivity to CME density, insertion propagation direction, and toroidal flux through multiple simulations.

Results. Our new method effectively reproduces magnetic field strength in situ measurements at 0.43 AU and 0.99 AU. The magnetic and plasma in situ data from SolO, located approximately along the mid-Sun-Earth line, were crucial for refining input parameters and improving the predictive accuracy at L1. Compared with the flux-constraining post-eruption arcade (PEA) method for this case study, at 0.99 AU, the PEA method underestimates the peak magnetic field by 13%, while the helicity-based method underestimates it by 19%

Conclusions. Our helicity-based flux estimation method shows promise for constraining CME input parameters in spheromak CME in EUHFORIA and closely matches in situ magnetic field measurements. Incorporating diverse CME events observed by multiple spacecraft will enable more robust assessments of the method’s reliability, efficiency, and compatibility relative to other approaches, and will help clarify its suitability for use with different CME models.