Turbulence properties of interplanetary coronal mass ejection flux ropes at 1 au

Abstract

ABSTRACT Interplanetary coronal mass ejection (ICME) is a massive, coherent magnetic structure emitting from the Sun in interplanetary space and plays an essential role in space weather processes. Here, we focus on determining the turbulent characteristics of magnetic field fluctuations in 358 ICMEs magnetic flux ropes (MFR) at 1 au using Wind spacecraft data. We observed that during injection, inertial, and dissipation scales, the average spectral index of the analysed MFRs is −1.70 ± 0.26, −1.64 ± 0.06, and −2.31 ± 0.40, respectively. It implies that overall the turbulence inside the ICME MFR has a Kolmogorow (f−5/3) type spectrum. We observe the nature of the spectral index to be unaffected by the MFR boundary and the presence of a background magnetic field. Thus, coherent MFRs show some turbulent characteristics. The low compressibility value during injection and the inertial scale indicate that Alfvénic fluctuations may dominate at these scales. We observe spectral break at the dissipation scale, but low normalized magnetic helicity denied the role of wave activity. Therefore, thorough research of the causes of a spectral break during the ICME MFR is necessary. Our results are relevant to exploring the energy cascade process, plasma heating, and energetic particle modulation in low plasma beta structures.