Speaker
Description
The importance of magnetic helicity in understanding Coronal Mass Ejections (CMEs) is well recognised. Many studies have supported the idea that a dominant helicity accumulation in active regions (AR) can be a reason for CME eruptions. This study investigates its potential for constraining input parameters in inner heliospheric CME propagation models. We propose a new method to constrain the magnetic flux of the spheromak CME model in the European Heliospheric Forecasting Information Asset (EUHFORIA) by utilising the CME's helicity content. This methodology provides a direct and quantitative inference of the helicity content of the CME. As a proof of concept, we analyse the CME observed on 10 March 2022 from NOAA AR 12962, observed in situ by both Solar Orbiter (SolO) and WIND, along with remote sensing observations. A helicity difference was observed in the pre- and post-eruptive phases of the source active region and was attributed to the corresponding CME. We relate the eruption-related magnetic helicity budget to the axial field of the spheromak model using the Graduated Cylindrical Shell CME forward-modelling technique. We identify axial strength as the magnetic field at the spheromak’s axis ($B_{spheromak}$). The toroidal magnetic flux is derived from $B_{spheromak}$ and the CME’s geometrical parameters. The EUHFORIA simulation results are compared with in situ magnetic field and plasma measurements from SolO at 0.43 AU and WIND at 0.99 AU to assess the method's reliability. The calculated magnetic flux from the CME’s helicity content shows that our method effectively reproduces magnetic field in situ measurements at 0.43 AU and 0.99 AU. The in situ data from SolO, approximately in the middle of the Sun-Earth line, were crucial for refining input parameters to improve the predictive accuracy at L1, highlighting the importance of studying multi-spacecraft observed events at different radial distances. The simulation results show that the peak magnetic field magnitude at $\sim$1 AU is underestimated by 19%. The power-law index with which the magnetic field magnitude is found to vary from 21.5 $R_{s}$ to 2 AU is estimated as -1.6.
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