One of the most striking observations made by Parker Solar Probe during its first solar encounter is the omnipresence of rapid polarity reversals in a magnetic field that is otherwise mostly radial. These so-called switchbacks strongly affect the dynamics of the magnetic field. We concentrate here on their macroscopic properties. First, we find that these structures are self-similar, and have neither a characteristic magnitude, nor a characteristic duration. Their waiting time statistics shows evidence for aggregation. The associated long memory resides in their occurrence rate, and is not inherent to the background fluctuations. Interestingly, the spectral properties of inertial range turbulence differ inside and outside of switchback structures; in the latter the 1/f range extends to higher frequencies. These results suggest that outside of these structures we are in the presence of lower amplitude fluctuations with a shorter turbulent inertial range. We conjecture that these correspond to a pristine solar wind.

We discuss the solar wind electron temperatures T e as measured in the nascent solar wind by Parker Solar Probe during its first perihelion pass. The measurements have been obtained by fitting the high frequency part of Quasi-Thermal Noise spectra recorded on-board by the Radio Frequency Spectrometer (Pulupa et al. 2017). In addition we compare these measurements with those obtained by the electrostatic analyzer Halekas & al. (2019). These first electron observations show an anti-correlation between T e and the wind bulk speed V : this anti-correlation is most likely the remnant of the well-known mapping observed at 1 AU and beyond between the fast wind and its coronal hole sources, where electrons are observed to be cooler than in the quiet corona. We also revisit HELIOS electron temperature measurements and show, for the first time, that an in-situ (T e , V) anti-correlation is well observed at 0.3 AU but disappears as the wind expands, evolves and mixes with different electron temperature gradients for different wind speeds.