Fully kinetic simulations of electron-scale plasma turbulence in the inner heliosphere: a pathfinder for future spacecraft missions

We present numerical results from high-resolution fully kinetic simulations of plasma turbulence under the near-Sun conditions encountered by Parker Solar Probe during its first perihelion, characterized by a low plasma beta and a large level of turbulent fluctuations. The recovered spectral properties are in agreement with those from PSP observations and recent high-resolution hybrid simulations just below the ion characteristic scales, i.e., the spectrum of the magnetic field exhibits a steep transition region with a spectral index compatible with -11/3. When the electron scales are reached a spectral break is observed and the spectrum steepens while still showing a clear power law. We discuss theoretical predictions for such a spectral behavior, based on a two-fluid model which assumes that a self-similar energy transfer across scales is occurring, without the need to include any kinetic process. We also analyse the role of magnetic reconnection and the statistics of reconnection events, as well as signatures in the proton and electron distribution functions hinting at mechanisms for energy dissipation. The results of this work represent a step forward in understanding the processes responsible for particle heating and acceleration and therefore on the origin of the solar wind and coronal heating. Furthermore, they allow for reliable predictions for future spacecraft missions investigating electron-scale physics in low-beta plasmas.