A new four‐plasma categorization scheme for the solar wind

Abstract

A three-parameter algebraic scheme is developed to categorize the solar wind at 1 AU into four plasma types: coronal-hole-origin plasma, streamer-belt-origin plasma, sector-reversal-region plasma, and ejecta. The three parameters are the proton-specific entropy S p = T p /n p 2/3 , the proton Alfvén speed v A , and the proton temperature T p compared with a velocity-dependent expected temperature. Four measurements are needed to apply the scheme: the proton number density n p , the proton temperature T p , the magnetic field strength B, and the solar wind speed v sw . The 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 four solar cycles and to the 1998-2008 ACE data set. The statistical properties of the four types of plasma are examined. The sector-reversal-region plasma is found to have statistically low alpha-to-proton density ratios and high Alfvén Mach numbers. The statistical relations between the proton and alpha-particle-specific entropies and oxygen and carbon charge-state-density ratios S p , S α , O 7+ /O 6+ , and C 6+ /C 5+ from ACE are examined for the four types of plasma: the patterns observed imply a connection between sector-reversal-region plasma and ejecta and a connection between streamer-belt-origin plasma and coronal-hole-origin plasma. Plasma occurrence rates are examined and solar cycle patterns are found for ejecta, for coronal-hole-origin plasma, and for sector-reversal-region plasma.

The proton and electron radiation belts at geosynchronous orbit: Statistics and behavior during high‐speed stream‐driven storms

“…The second panel shows that the electron radiation belt density recoveries tend to occur after the dawnward‐duskward reversal through zero of the solar wind flow direction, i.e., after the CIR stream interface passes, in what is compressed coronal hole origin solar wind plasma. This is corroborated by the red S p curve in Figure (fourth panel) showing that the electron number density recoveries occur in high‐entropy coronal hole plasma [ Xu and Borovsky , ]. The green curve in Figure (fourth panel) shows that the electron recoveries tend to occur after the peak compression (maximum of B mag ) of the CIR, which occurs near the stream interface.…”

“…This is also confirmed by the red and green curves in Figure (fourth panel); the red S p curve shows the dropouts occurring in low‐entropy (streamer belt or sector‐reversal‐region) solar wind [cf. Xu and Borovsky , ], and the green B mag curve shows that the dropouts occur before the peak of the compression of the CIR. The blue n sw curve in Figure (fourth panel) indicates that the temporal occurrence of the electron radiation belt density dropout is associated with a peak of the solar wind number density, which also corresponds to a peak in the solar wind ram pressure.…”

“…In Figure (second panel) superposed averages of the solar wind number density are plotted for the two sets of storms. Prior to the storm the superposed average of the density of the streamer belt plasma is slightly higher than the density of the coronal hole plasma during the storm; this is caused by the presence of noncompressive density enhancements in the solar wind [ Gosling et al , ; Borrini et al , ] likely to be sector‐reversal‐region plasma [ Xu and Borovsky , ]. Near the time of storm onset the number density is particularly high owing to the compression of the solar wind in the corotating interaction region [ Gosling et al , ; Richter and Luttrell , ; Borovsky and Denton , ].…”

Evolution of an equatorial coronal hole structure and the released coronal hole wind stream: Carrington rotations 2039 to 2050

“…To characterize observed solar-wind packages by type, we use the categorisation scheme from Xu & Borovsky (2015). This scheme defines four categories of solar wind: coronal hole wind plasma, ejecta plasma, and two slow solar wind categories, namely sector-reversal region plasma and streamer-belt plasma.…”

Book of Proceedings Tenth Workshop Primorsko, Bulgaria 2018

“…et al, 2012], [Feldman U. et al, 2005]). In [Xu F. & Borovsky J.E., 2015], a classification was proposed with dividing of the solar wind plasma into 4 categories, based on coronal sources: coronalhole-origin plasma, streamer-belt-origin plasma, sector-reversal-region plasma and transient events (such as CMEs). The division was made on the basis of quantitative criteria for three parameters: entropy of protons, their Alfvén velocity, and their temperature relative to the expected from the wind speed.…”