Solar phenomena move about and can travel at a few hundred meters per second when they first appear. The solar wind is a stream of plasma released from the Sun's upper atmosphere. It consists of mostly electrons and protons with energies usually between 1.5 and 10 keV. The stream of particles varies in density, temperature and speed over time and over solar longitude. These particles can escape the Sun's gravity because of their high energy. The solar wind is divided into the slow solar wind and the fast solar wind. The slow solar wind has a velocity of about , a temperature
Degree of ionization plasma is in a "Coulomb-collision dominated regime", i.e. when formula_9, which can correspond to a degree of ionization as low as 0.01%. A "partially" or "weakly ionized gas" means the plasma is not dominated by Coulomb collisions, i.e. when formula_10. A particular case of fully ionizes gases are very hot thermonuclear plasmas, such as plasmas artificially produced in nuclear explosions or naturally formed in our Sun and all stars in the universe. Stars contain largely hydrogen and helium gases, that are "fully ionized" into electrons, protons (H) and helium ions (He). Equations to characterize such very hot, fully ionized thermonuclear