Turbulent Cascade, Intermittency and Energy Transfer Rate Across a Coronal Mass Ejection Encounter

The properties of solar wind turbulence are examined before, during and after a coronal mass ejection (CME) detected by the Wind spacecraft on July 2012. The power-law scaling of the structure functions, providing information on the power spectral density and flatness of the velocity, magnetic filed and density fluctuations, were examined. The third-order moment scaling law for incompressible, isotropic magnetohydrodynamic turbulence was observed in the upstream and downstream solar wind, as well as in the CME sheath and magnetic cloud. This suggests that the turbulence could develop sufficiently after the shock, or that the sheath and cloud regions turbulence was robustly preserved even during the mixing with the solar wind plasma.The turbulent energy transfer rate was thus evaluated in each of the regions. The CME sheath shows an increase of energy transfer rate, as expected from the lower level of Alfvénic fluctuations and suggesting the role of the shock-wind interaction as an additional source of energy for the turbulent cascade.