Turbulence Transport Modeling and PSP Observations

The Parker Solar Probe (PSP) has made two orbits of the Sun since its launch in August 2018. The PSP achieved its first orbit perihelion on November 6, 2018, reaching a heliocentric distance of about 0.16 au. Here, we study the evolution of fully developed turbulence associated with the slow solar wind along the PSP trajectory between ~ 0.16 au and ~ 0.7 au, comparing observations to a theoretical turbulence transport model. Several turbulence quantities, such as the energy in forward and backward propagating modes, the fluctuating magnetic and kinetic energy, the normalized residual energy, the normalized cross-helicity, and the correlation lengths are determined from the PSP measurements along its trajectory between ~0.16 to ~0.7 au. The evolution of the PSP derived turbulence quantities are compared to the numerical solutions of the theoretical nearly incompressible magnetohydrodynamic (NI MHD) turbulence transport model recently developed by Zank et al. 2017. We find good agreement between the theoretical and observed results, suggesting that such a turbulence transport model can explain the turbulent evolution in the slow wind along the PSP trajectory.