Phenomenological Evaluation of the Electron Density-Based Péclet Number of Near-Earth Solar Wind Turbulence

The electron density-based Péclet number has been measured for the first time in the solar wind, alongside a measure of the magnetic Reynolds number. The Péclet number is an important characteristic of energy and particle transport. High Péclet numbers indicate that particle advection dominates diffusion of energy. The Péclet number is measured using the correlation scale and the Taylor microscale at 1 au, alongside the magnetic Reynolds number, using the same two scales. These scales are determined by utilizing in situ magnetic field and electron density fluctuations, deduced from spacecraft potential data from the Magnetospheric MultiScale mission (MMS). We find that the electron density fluctuations produce a much smaller scalar Taylor microscale of (Formula presented.) km, than is estimated from the magnetic field; (Formula presented.) km. Conversely, the estimated Reynolds number for the magnetic field is found to be much smaller, (Formula presented.), in comparison to the electron density-based Péclet number; (Formula presented.). We consider several possibilities as to why the difference in these observations is present. Instrumental effects due to different sampling rates and instrumental noise floors can influence the measurement of the Taylor microscale. In a physical sense, the difference could reflect the fluctuations of magnetic and electron densities holding different properties. This study is the first of its kind to measure the Péclet number in the solar wind.