Spectrum of kinetic plasma turbulence at 0.3–0.9 astronomical units from the Sun

We investigate spectral properties of turbulence in the solar wind that is a weakly collisional astrophysical plasma, accessible to situ observations. Using Helios search coil magnetometer measurements fast wind, inner heliosphere, we focus on turbulent magnetic fluctuations at scales smaller than ion characteristic scales, so-called kinetic plasma turbulence. At such small show power spectra between 0.3 and 0.9 AU from Sun have generic shape $\ensuremath{\sim}{f}^{\ensuremath{-}8/3}exp(\ensuremath{-}f/{f}_{d})$, where dissipation frequency ${f}_{d}$ correlated with Doppler shifted ${f}_{\ensuremath{\rho}e}$ electron Larmor radius. This behavior statistically significant: all observed are well described by this model, ${f}_{d}={f}_{\ensuremath{\rho}e}/1.8$. Our results indicate gyroradius plays role scale marks end electromagnetic cascade wind.