The Correlation Function for Magnetic Field Fluctuations at Ion Dissipation Scales in the Solar Wind

Le résumé fourni par la source

This study investigates energy dissipation in small-scale solar wind turbulence using a novel approach to autocorrelation function analysis leveraging high-resolution data from the Magnetospheric Multiscale Mission (MMS). We analyze magnetic field fluctuations at ion dissipation scales, focusing on short 20-second intervals to isolate dissipation-scale dynamics. Using MMS’s fluxgate magnetometer, fast plasma investigation, and energetic particle detector, we compute normalized correlation functions as functions of solar wind parameters, including interplanetary magnetic field cone angle and solar wind speed. Our results show that turbulence decorrelates over short spatial scales ($\sim$ 100-1000 km), with faster decorrelation in the compressional component compared to the transverse components. We find that the transverse correlation lengths differ most when the interplanetary magnetic field is nearly perpendicular to the solar wind flow (cone angle $\sim 90^{\circ}$), and that they vary approximately as the inverse sine of the cone angle. The characteristics of the correlation length suggest that the turbulence observed is primarily two-dimensional. These findings highlight the anisotropic nature of dissipation-scale turbulence and its dependence on solar wind conditions, providing insights into energy transfer in space plasmas.

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