Two Correlations with Enhancement Near the Proton Gyroradius Scale in Solar Wind Turbulence: Parker Solar Probe (PSP) and Wind Observations

Abstract

Based on the Parker Solar Probe mission, this paper presents the observations of two correlations in solar wind turbulence near the Sun for the first time, demonstrating the clear existence of the following two correlations. One is positive correlation between the proton temperature and turbulent magnetic energy density. The other is negative correlation between the spectral index and magnetic helicity. It is found that the former correlation has a maximum correlation coefficient (CC) at the wavenumber k rho ( p ) similar or equal to 0.5 (rho ( p ) being the proton thermal gyroradius), and the latter correlation has a maximum absolute value of CC at k rho ( p ) similar or equal to 1.8. In addition, investigations based on 11 yr of Wind observations reveal that the dimensionless wavenumbers (k rho ( p )) corresponding to the maximum (absolute) values of CC remain nearly the same for different data sets. These results tend to suggest that the two correlations enhanced near the proton gyroradius scale would be a common feature of solar wind turbulence.