Numerical simulations of self-consistently generated κ distributions in the solar wind and solar corona

Abstract:

In a previous study (Randol and Christian, submitted to JGR, April 2014), numerical simulations of protons and anti-protons obeying Coulomb’s law provided key insight into the self-consistent generation of κ distributions in space plasmas. In that study, the velocity distribution function (VDF) first formed a tail with the common spectral index of -5 and then gradually became a κ-r distribution, with κ = 1.5, corresponding to the common spectrum. The form of this distribution was found to relate to the electric field distribution function (EDF). These results were robust to a range of initialized densities and thermal speeds; however, this range of parameters did not include values close to those of the solar wind at 1 AU. Here we report on simulations of the same type but for a broader range of parameters, including those of the solar wind and corona. Our earliest findings indicate a lack of consistency in the VDF with the common spectrum, the cause of which again lies in the EDF. The results are instructive for understanding the solar wind ion VDF core and tail, as well as for κ distributed plasmas in general.