Magnetic Field Fluctuations in CME-driven Sheath Regions

The sheath regions driven by coronal mass ejections (CMEs) are large-scale heliospheric structures where magnetic field fluctuations are observed over various temporal scales. Their internal structure and nature of embedded fluctuations are currently poorly understood. We report here the key characteristics of magnetic field fluctuations in CME-driven sheaths, including their spectral index, intermittency, amplitude and compressibility. The results highlight the gradual formation of sheaths over several days as they propagate through interplanetary and the presence of intermittent coherent structures such as strong current sheets. The Jensen-Shannon permutation entropy and complexity analysis suggest that sheath fluctuations are stochastic, but have lower entropy and higher complexity than the preceding wind. We also show the analysis results during the slow sheath at ~0.5 AU detected by Parker Solar Probe, highlighting that slow CMEs can have prominent sheaths with distinct fluctuation properties.