Whitepaper #432 in the Decadal Survey for Solar and Space Physics (Heliophysics) 2024-2033. Main topics: basic research. Additional topics: fundamental space plasma theory; inner heliosphere; space-based missions/projects.
The current state of the art thermal particle measurements in the solar wind are insufficient to address many long standing, fundamental physical processes. The solar wind exhibits multiple particle populations for each particle species. We can resolve the electron populations but only separate the ion species. Thus, we are inherently limited in our understanding of the solar wind kinetics.