MMS Insights into CME Driven Sub-Alfv\'enic Solar Wind at 1 AU
Abstract
We report the properties of electron distributions and turbulence during a Coronal Mass Ejection (CME) in April 2023 observed by Magnetospheric Multiscale (MMS). The CME exhibits a clear sheath and magnetic cloud (MC), and within the MC, the solar wind becomes sub-Alfv\'enic for two hours. We investigate plasma and turbulence properties of the sub-Alfv\'enic CME wind and compare them with those in the super-Alfv\'enic solar wind in the MC and CME sheath. Electrons within the sub-Alfv\'enic MC show significantly higher temperatures than those in the CME sheath and the super-Alfv\'enic MC, with their one-dimensional distributions revealing super-thermal tail and a depletion in electron populations between 15-50 eV. Within the CME sheath, isolated regions of electron heating are observed, where parallel energy flux is enhanced up to ~1 keV. Magnetic field fluctuations within the sub-Alfv\'enic MC interval exhibit negligible cross helicity and steeper-than-Kolmogorov scaling in the inertial range, with no clear spectral break. These fluctuations also show reduced intermittency at ion and sub-ion scales, emerging intermittency at electron scales, and weak magnetic compressibility. Together, these observations point to the presence of weak magnetohydrodynamic (MHD) turbulence within the sub-Alfv\'enic MC, resembling conditions commonly observed in planetary magnetospheres such as Jupiter's.
Keywords
Cite
@article{arxiv.2604.12000,
title = {MMS Insights into CME Driven Sub-Alfv\'enic Solar Wind at 1 AU},
author = {Harsha Gurram and Li-Jen Chen and Matthew R. Argall and Subash Adhikari and Lynn B. Wilson and Jason R. Shuster and Victoria D. Wilder},
journal= {arXiv preprint arXiv:2604.12000},
year = {2026}
}
Comments
10 pages, 5 figures, 1 table