A Versatile 4-Plasma Categorization Scheme for the Solar Wind: Exploring the Statistical Properties of Plasmas of Different Origins

A 3-parameter algebraic scheme is developed to categorize the solar wind at 1 AU into 4 plasma types: coronal-hole-origin plasma, streamer-belt-origin plasma, sector-reversal-region plasma, and ejecta. The three parameters are the proton specific entropy, the proton Alfven speed, and the proton temperature T_p compared with a velocity-dependent expected temperature. The scheme does not use the time history of the wind nor does it use heavy-ion charge states. The 3-parameter scheme is tested and is found to be more accurate than existing categorization schemes. The categorization scheme is applied to the 1963-2013 OMNI2 data set spanning 4 solar cycles and to ACE. The statistical properties of the 4 types of plasma are examined. The sector-reversal-region plasma is found to have statistically low alpha-to-proton density ratios and high Alfven Mach numbers. The outward-inward imbalance of the solar-wind fluctuations are high in coronal-hole-origin plasma, modest in streamer-belt-origin plasma, very low in sector-reversal-region plasma, and gone in ejecta. The statistical relations between the proton and alpha-particle specific entropies and the oxygen and carbon charge-state density ratios are examined for the four types of plasma: the patterns observed imply a connection at the Sun between sector-reversal-region plasma and ejecta and a connection between streamer-belt-origin plasma and coronal-hole-origin plasma. The magnetic structure and plasma structure of the solar wind for the four different types of plasmas are overviewed.