Classification Scheme for Solar Wind

Abstract

A binary classification of solar wind types is given according to three main hydrodynamic parameters—the proton speed, the proton temperature, and the proton density. Boundaries between the fast–hot–dense, fast–hot–rarefied, fast–cold–dense, fast–cold–rarefied, slow–hot–dense, slow–hot–rarefied, slow–cold–dense, and slow–cold–rarefied solar wind types are specified in the space of these variables. These types arise at different frequencies and originate from different sorts of solar activity. An analysis of 1-minute data from the OMNIWeb database is performed over the period from January 1, 2016, to September 30, 2017. In some cases, this classification scheme, which is quite simple and clear, allows one to identify the sources of the solar wind (coronal holes and coronal mass ejections), as well as to reveal long-term trends. The proposed scheme is compared with the methods used earlier in the literature to classify solar wind types.