Turbulence and Anomalous Resistivity inside Near-Earth Magnetic Clouds

Abstract

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.