Assessing Accumulation and Erosion of Interplanetary Coronal Mass Ejections Using Lined-up Spacecraft
8 affiliations
- 1Indian Institute of Technology Roorkee
- 2University of Helsinki
- 3National Institute for Astrophysics
- 4Institute for Plasma Science and Technology (ISTP)
- 5KTH Royal Institute of Technology
- 6NASA Goddard Space Flight Center
- 7Università di Genova
- 8University College London
Abstract
Interplanetary coronal mass ejections (ICMEs), the large-scale solar transients carrying flux ropes (FRs), may evolve in different ways, including erosion and/or accumulation of magnetic field lines while being involved in magnetic reconnection with ambient solar wind and often with other nearby ICMEs and solar wind structures. In this Letter, for the first time utilizing a rare alignment of spacecraft, we analyse the multiscale radial evolution of two ICMEs—observed by spacecraft pairs with minimal angular separations of 2 . ° 2 and 1 . ° 1, and radial separations of 0.15 and 0.05 au, respectively—due to erosion and accumulation. We derive their magnetic helicity and cross helicity, residual and average magnetic energy, FR radial size, temporal extension of their helical structures, and the core’s characteristic scale size, and compare these parameters at the radial distances of the lined-up spacecraft to obtain their radial scaling. We find that if an expanding FR undergoes erosion at its outer layer during heliospheric propagation, its overall size expansion rate is lower than that of its core, where field line helicity is maximum. Conversely, during field line accumulation or merging, the expansion rate of FR overall size is higher than that of its core. Furthermore, erosion is indicated by a decreasing dominance of magnetic energy relative to total energy and a higher rate of average magnetic energy decay than ideally expected. These results demonstrate that coordinated multispacecraft observations can distinguish between erosion and accumulation processes in ICME FRs and provide new constraints on their dynamical evolution in the heliosphere.
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BibTeX
@article{pal2026assessing,
title = {{Assessing Accumulation and Erosion of Interplanetary Coronal Mass Ejections Using Lined-up Spacecraft}},
author = {Sanchita Pal and Simon Good and Daniele Telloni and Luca Sorriso-Valvo and Jaye Verniero and Lan K. Jian and Sabrina Guastavino and Teresa Nieves-Chinchilla and Georgios Nicolaou},
journal = {The Astrophysical Journal Letters},
year = {2026},
month = oct,
doi = {10.3847/2041-8213/aeac5a},
url = {https://iopscience.iop.org/article/10.3847/2041-8213/aeac5a},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Assessing Accumulation and Erosion of Interplanetary Coronal Mass Ejections Using Lined-up Spacecraft
AU - Sanchita Pal
AU - Simon Good
AU - Daniele Telloni
AU - Luca Sorriso-Valvo
AU - Jaye Verniero
AU - Lan K. Jian
AU - Sabrina Guastavino
AU - Teresa Nieves-Chinchilla
AU - Georgios Nicolaou
PY - 2026
DA - 2026/10/23
JO - The Astrophysical Journal Letters
DO - 10.3847/2041-8213/aeac5a
UR - https://iopscience.iop.org/article/10.3847/2041-8213/aeac5a
AB - Interplanetary coronal mass ejections (ICMEs), the large-scale solar transients carrying flux ropes (FRs), may evolve in different ways, including erosion and/or accumulation of magnetic field lines while being involved in magnetic reconnection with ambient solar wind and often with other nearby ICMEs and solar wind structures. In this Letter, for the first time utilizing a rare alignment of spacecraft, we analyse the multiscale radial evolution of two ICMEs—observed by spacecraft pairs with minimal angular separations of 2 . ° 2 and 1 . ° 1, and radial separations of 0.15 and 0.05 au, respectively—due to erosion and accumulation. We derive their magnetic helicity and cross helicity, residual and average magnetic energy, FR radial size, temporal extension of their helical structures, and the core’s characteristic scale size, and compare these parameters at the radial distances of the lined-up spacecraft to obtain their radial scaling. We find that if an expanding FR undergoes erosion at its outer layer during heliospheric propagation, its overall size expansion rate is lower than that of its core, where field line helicity is maximum. Conversely, during field line accumulation or merging, the expansion rate of FR overall size is higher than that of its core. Furthermore, erosion is indicated by a decreasing dominance of magnetic energy relative to total energy and a higher rate of average magnetic energy decay than ideally expected. These results demonstrate that coordinated multispacecraft observations can distinguish between erosion and accumulation processes in ICME FRs and provide new constraints on their dynamical evolution in the heliosphere.
SN - 2041-8205
SN - 2041-8213
ER -