Solar Wind Structure List Since 1963

This file contains a classification of near-Earth solar wind structure types since the start of the OMNI data set in 1963. The classification is primarily based on examination of the solar wind data (plasma and magnetic field) as described in Richardson and Cane (2012) \"Near-earth solar wind flows and related geomagnetic activity during more than four solar cycles (1963–2011)\", J. Space Weather Space Clim. 2 (2012) A02 DOI: 10.1051/swsc/2012003 and references therein. Where there are gaps in the solar wind data, other data are considered, such as the galactic cosmic ray intensity from neutron monitors and spacecraft (e.g., for evidence of cosmic ray modulations) and geomagnetic indices (e.g.,, aa, Dst, Kp, C9, to identify intervals of geomagnetic activity) associated with the passage of solar wind structures. The structure types are: Category 1) Transient flows originating with coronal mass ejections (CMEs) at the Sun, including interplanetary coronal mass ejections (ICMEs) and the associated upstream shocks and postshock/sheath regions (see Zurbuchen & Richardson, Space Science Reviews (2006) 123: 31–43, DOI: 10.1007/s11214-006-9010-4, and references therein for discussion of the in-situ signatures of ICMEs). We collectively term these ‘‘CME-associated’’ flows. Category 2) Corotating high-speed streams, typically with solar wind speed V > ~450 km/s, that originate in coronal holes at the Sun. The properties of corotating high-speed streams near 1 AU were reviewed by Richardson, Living Rev. Sol. Phys. (2018) 15:1 https://doi.org/10.1007/s41116-017-0011-z, and include the formation of a region of compressed plasma, the ‘‘corotating (or \"stream\") interaction region’’ (CIR/SIR), at the leading edge of the stream as it interacts with the preceding slower, cooler, and denser solar wind. Since the source coronal holes may persist for longer than a solar rotation, a given stream may recur at the solar rotation period (~27 days as viewed from Earth). Category 3) Slower, interstream solar wind, typically associated with the streamer belt at the Sun (e.g., Feldman et al. J Geophys Res 86:5408–5416 (1981). https://doi.org/ 10.1029/JA086iA07p05408. Category 0) Unclear/uncertain intervals, e.g. due to data gaps/where the classification is unclear. The list consists of the start time (year/day of year/hour/min) of each structure type typically \"to the nearest hour\". Occasionally, the start time of a category 1 structure is given by passage of a shock. Caveats: This classification was carried out in stages since 1999 to present, and the criteria used are not guaranteed to be be completely uniform throughout. The transition between other categories and slow solar wind may be subjective. Although slow solar wind, from the above definition, may have speeds below ~450 km/s, there are corotating streams which barely exceed this level, and in some cases, there are clear discontinuities marking the start of the slow solar wind. The fast-slow transition is also often rather gradual and an exact transition time difficult to determine.