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
Diffusion damping during which simple atoms, e.g. hydrogen and helium, began to form in the cooling, but still very hot, soup of protons, electrons and photons that composed the universe. Prior to the recombination epoch, this "soup", a plasma, was largely opaque to the electromagnetic radiation of photons. This meant that the permanently excited photons were scattered by the protons and electrons too often to travel very far in straight lines. During the recombination epoch, the universe cooled rapidly as free electrons were captured by atomic nuclei; atoms formed from their constituent parts and the universe became transparent: the amount of photon