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Abstract
Coronal mass ejections (CMEs) are large-scale eruptions with a typical radial size at 1 au of 0.21 au but their angular width in interplanetary space is still mostly unknown, especially for the magnetic ejecta (ME) part of the CME. We take advantage of STEREO-A angular separation of 20°–60° from the Sun–Earth line from 2020 October to 2022 August, and perform a two-part study to constrain the angular width of MEs in the ecliptic plane: (a) we study all CMEs that are observed remotely to propagate between the Sun–STEREO-A and the Sun–Earth lines and determine how many impact one or both spacecraft in situ, and (b) we investigate all in situ measurements at STEREO-A or at L1 of CMEs during the same time period to quantify how many are measured by the two spacecraft. A key finding is that out of 21 CMEs propagating within 30° of either spacecraft only four impacted both spacecraft and none provided clean magnetic cloud-like signatures at both spacecraft. Combining the two approaches, we conclude that the typical angular width of an ME at 1 au is ∼20°–30°, or 2–3 times less than often assumed and consistent with a 2:1 elliptical cross section of an ellipsoidal ME. We discuss the consequences of this finding for future multi-spacecraft mission designs and for the coherence of CMEs.
Department
Space Science Center
Publication Date
2-1-2024
Journal Title
The Astrophysical Journal
Publisher
American Astronomical Society
Digital Object Identifier (DOI)
Document Type
Article
Recommended Citation
Noé Lugaz et al 2024 ApJ 962 193 DOI 10.3847/1538-4357/ad17b9
Rights
© 2024. The Author(s).
Comments
This is an open access article published by American Astronomical Society in The Astrophysical Journal in 2024, available online: https://dx.doi.org/10.3847/1538-4357/ad17b9