Understanding the effects of spacecraft trajectories through solar coronal mass ejection flux ropes using 3DCOREweb

TL;DR

This paper uses 3D modeling to analyze how spacecraft position affects the in situ signatures of CMEs, revealing key differences based on trajectory and flux rope properties, aiding interpretation of observational data.

Contribution

It introduces a comprehensive 3D flux rope model to simulate in situ CME signatures at various spacecraft positions, enhancing understanding of flux rope type identification.

Findings

Apex hits show distinct signatures compared to flank encounters.

Low twist CMEs can produce non-rotating signatures in flank encounters.

Different flux rope types are clearly distinguishable in in situ data.

Abstract

This study investigates the impact of spacecraft positioning and trajectory on in situ signatures of coronal mass ejections (CMEs). Employing the 3DCORE model, a 3D flux rope model that can generate in situ profiles for any given point in space and time, we conduct forward modeling to analyze such signatures for various latitudinal and longitudinal positions, with respect to the flux rope apex, at 0.8~au. Using this approach, we explore the appearance of the resulting in situ profiles for different flux rope types, with different handedness and inclination angles, for both high and low twist CMEs. Our findings reveal that CMEs exhibit distinct differences in signatures between apex hits and flank encounters, with the latter displaying elongated profiles with reduced rotation. However, constant, non-rotating in situ signatures are only observed for flank encounters of low twist CMEs, suggesting the existence of untwisted magnetic field lines within CME legs. Additionally, our study confirms the unambiguous appearance of different flux rope types in in situ signatures, contributing to the broader understanding and interpretation of observational data. Given the model assumptions, this may refute trajectory effects to be the cause for mismatching flux rope types as identified in solar signatures. While acknowledging limitations inherent in our model, such as the assumption of constant twist and non-deformable torus-like shape, we still draw relevant conclusions within the context of global magnetic field structures of CMEs and the potential for distinguishing flux rope types based on in situ observations.