Context. The pressure and energy density of the gas and magnetic field inside solar coronal mass ejections (in relation to that in the ambient solar wind) is thought to play an important role in determining their dynamics as they propagate through the heliosphere. Aims. We compare the specific energy (erg g −1 ), comprising kinetic (H k ), thermal (H th ) and magnetic field (H mag ) contributions, inside magnetic clouds (MCs) and the solar wind background. We examine whether the excess thermal + magnetic pressure and specific energy inside MCs (relative to the background) are correlated with their propagation and internal expansion speeds. We consider whether the excess thermal + magnetic specific energy inside MCs might cause them to resemble rigid bodies in the context of aerodynamic drag. Methods. We used near-Earth in situ data from the WIND spacecraft to identify a sample of 152 well-observed interplanetary coronal mass ejections and their MC counterparts. We compared various metrics based on these data to address our questions.Results. We find that the total specific energy (H) inside MCs is approximately equal to that in the background solar wind. We find that the excess (thermal + magnetic) pressure and specific energy are not well correlated with the near-Earth propagation and expansion speeds. We find that the excess thermal+magnetic specific energy is greater or equivalent to the specific kinetic energy of the solar wind incident in 81-89 % of the MCs we study. This might explain how MCs retain their structural integrity and resist deformation by the solar wind bulk flow.
Context. The pressure and energy density of the gas and magnetic field inside solar coronal mass ejections (in relation to that in the ambient solar wind) is thought to play an important role in determining their dynamics as they propagate through the heliosphere. Aims. We compare the specific energy (erg g −1 ) [comprising kinetic (H k ), thermal (H th ) and magnetic field (H mag ) contributions] inside MCs and the solar wind background. We examine if the excess thermal + magnetic pressure and specific energy inside MCs (relative to the background) is correlated with their propagation and internal expansion speeds. We ask if the excess thermal + magnetic specific energy inside MCs might make them resemble rigid bodies in the context of aerodynamic drag. Methods. We use near-Earth in-situ data from the WIND spacecraft to identify a sample of 152 well observed interplanetary coronal mass ejections and their MC counterparts. We compute various metrics using these data to address our questions.Results. We find that the total specific energy (H) inside MCs is approximately equal to that in the background solar wind. We find that the the excess (thermal + magnetic) pressure and specific energy are not well correlated with the near-Earth propagation and expansion speeds. We find that the excess thermal+magnetic specific energy the specific kinetic energy of the solar wind incident on 81-89 % of the MCs we study. This might explain how MCs retain their structural integrity and resist deformation by the solar wind bulk flow.
We use in-situ data from the Wind spacecraft to survey the amplitude of turbulent fluctuations in the proton density and total magnetic field inside a large sample of near-Earth magnetic clouds (MCs) associated with coronal mass ejections (CMEs) from the Sun. We find that the most probable value of the modulation index for proton density fluctuations (δn p /n p ) inside MCs ranges from 0.13 to 0.16, while the most probable values for the modulation index of the total magnetic field fluctuations (δB/B) range from 0.04 to 0.05. We also find that the most probable value of the Mach number fluctuations (δM) inside MCs is ≈ 0.1. The anomalous resistivity inside near-Earth MCs arising from electron scattering due to turbulent magnetic field fluctuations exceeds the (commonly used) Spitzer resistivity by a factor of ≈ 500 − 1000. The enhanced Joule heating arising from this anomalous resistivity could impact our understanding of the energetics of CME propagation.
We use in-situ data from the Wind spacecraft to survey the amplitude of turbulent fluctuations in the proton density and total magnetic field inside a large sample of near-Earth magnetic clouds (MCs) associated with coronal mass ejections (CMEs) from the Sun. We find that the most probable value of the modulation index for proton density fluctuations (δnp/np) inside MCs ranges from 0.13 to 0.16, while the most probable values for the modulation index of the total magnetic field fluctuations (δB/B) range from 0.04 to 0.05. We also find that the most probable value of the Mach number fluctuations (δM) inside MCs is ≈0.1. The anomalous resistivity inside near-Earth MCs arising from electron scattering due to turbulent magnetic field fluctuations exceeds the (commonly used) Spitzer resistivity by a factor of ≈500 − 1000. The enhanced Joule heating arising from this anomalous resistivity could impact our understanding of the energetics of CME propagation.
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