2025/05/23 by Soumyaranjan Khuntia, Wageesh Mishra, Khuntia, Soumyaranjan +1
Physics and Astronomy · #FOS: Physical sciences #Plasma Physics (physics.plasm-ph) #Solar and Space Plasma Dynamics #Solar and Stellar Astrophysics (astro-ph.SR) #Space Physics (physics.space-ph)
paper · pdf · doi:10.48550/arxiv.2505.18296
openalex publication_date 2025/05/23 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Understanding the thermal and turbulence properties of interplanetary coronal mass ejections (ICMEs) is essential for analyzing their evolution and interactions with the surrounding medium. This study explores these characteristics across different regions of two distinct ICMEs observed at 1 AU, utilizing in-situ measurements from the Wind spacecraft. The polytropic indices, Gammae for electrons and Gammap for protons) reveal significant deviations from adiabatic expansion, suggesting sustained heating mechanisms within the ICMEs even at 1AU. The effective polytropic index (Gammaeff) of the magnetic ejecta (ME) in both ICME1 and ICME2 is found to be near-isothermal (Gammaeff = 0.88 and 0.76), aligning with measurements near the Sun, highlighting consistent heating across heliospheric distances. Spectral analysis at the inertial scale reveals Kolmogorov-like turbulence in the fast ICME1's ME, while the ME of the slower ICME2 exhibits less developed turbulence with a shallower spectral index (alphaB). The turbulence analysis in the dissipation scale indicates that the ME of slower ICME2 is less affected by the ambient medium than the faster ICME2. The MEs of both ICMEs show magnetic compressibility much smaller than unity (CB < 1), suggesting dominant Alfvenic fluctuations in the MEs. Notably, the partial variance of increments (PVI) method identifies more intermittent structures, such as current sheets and reconnection sites, in the sheath and post-ICME regions. Higher PVI values correlate with regions of increased electron and proton temperature (for the sheath region), as well as higher CB values, highlighting their role in local energy dissipation. These results underscore the importance of ongoing heating and turbulence processes in shaping the evolution of ICMEs.