Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 International License.
Abstract
Simultaneous in situ measurements of coronal mass ejections (CMEs), including both plasma and magnetic field, by two spacecraft in radial alignment have been extremely rare. Here, we report on one such CME measured by Solar Orbiter (SolO) and Wind on 2021 November 3–5, while the spacecraft were radially separated by a heliocentric distance of 0.13 au and angularly by only 2.2°. We focus on the magnetic cloud (MC) part of the CME. We find notable changes in the R and N magnetic field components and in the speed profiles inside the MC between SolO and Wind. We observe a greater speed at the spacecraft farther away from the Sun without any clear compression signatures. Since the spacecraft are close to each other and computing fast magnetosonic wave speed inside the MC, we rule out temporal evolution as the reason for the observed differences, suggesting that spatial variations over 2.2° of the MC structure are at the heart of the observed discrepancies. Moreover, using shock properties at SolO, we forecast an arrival time 2 hr 30 minutes too late for a shock that is just 5 hr 31 minutes away from Wind. Predicting the north–south component of the magnetic field at Wind from SolO measurements leads to a relative error of 55%. These results show that even angular separations as low as 2.2° (or 0.03 au in arc length) between spacecraft can have a large impact on the observed CME properties, which raises the issue of the resolutions of current CME models, potentially affecting our forecasting capabilities.
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
F. Regnault et al 2024 ApJ 962 190
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/ad1883