Tracing Magnetic Helicity from the Solar Source Region to Interplanetary Space: A Multi-Spacecraft Analysis of the March 23, 2024 ICME

Recent multi-spacecraft observations show the complex structure of Interplanetary Coronal Mass Ejections (ICMEs) as they propagate through interplanetary space. These observations allow us to monitor magnetic-field-related parameters systematically across vast spatial domains. Among the measurable quantities, magnetic helicity is of particular interest as it is quasi-conserved even in resistive MHD. It serves as a robust measure of the magnetic field complexity and, consequently, provides a physically grounded tracer for linking the magnetic topology of the ICME’s source region in the low solar atmosphere to the large-scale magnetic configuration in interplanetary space.

We present the analysis of a flare/CME event (SOL2024-03-23T X1.1) paired with a study of the ICME’s flux rope global structure that presumably impacted Solar Orbiter (at a heliocentric distance of 0.39 AU), BepiColombo (0.58 AU), STEREO-A (0.96 AU), as well as Wind (0.99 AU).

To model the three-dimensional coronal magnetic field of the solar source active region (NOAA 13614), we employ a non-linear force-free (NLFF) extrapolation based on the recently developed machine-learning approach. To infer the properties of the associated CME at the different locations in interplanetary space, we apply the semi-empirical 3DCORE model to the individual in-situ spacecraft data. Based on the modeling of the underlying magnetic field structure, we are able to compute the magnetic helicity in the solar source region (using a finite-volume method) as well as in interplanetary space, the latter using a linear force-free ("Lundquist") and a nonlinear force-free ("Gold-Hoyle") approach. This approach allows us to trace its evolution continuously from the low corona to near-Earth space. Our broader objective is to establish consistent and physically meaningful helicity estimates across coronal and Heliospheric domains.