Galactic cosmic rays are the most energetic of particles found in space. The most prevalent are high-energy protons, but as with particles from the Sun, there are also much heavier ions, ranging from the nuclei of helium atoms (atomic weight four, or four times the weight of a proton) to the relatively abundant ions of iron (weight 56). And they travel outward at speeds that can considerably exceed most particles of solar origin. The reason for the great energies and high speeds of cosmic rays, and why they include heavy ions such as iron, nickel and zinc, is that they are propelled outward from cataclysms far more violent than any large solar flare. The source of most cosmic rays is thought to be explosions of entire stars (supernovae). The solar cycle is an approximately 11-year period of varying solar activity including solar maximum where the solar wind is strongest and solar minimum where the solar wind is weakest. Galactic cosmic rays create a continuous radiation dose throughout the Solar System that increases during solar minimum and decreases during solar maximum. Because cosmic rays are electrically charged they are deflected by magnetic fields, and their directions have been randomized, making it impossible to tell where they originated. However, cosmic rays in other regions of the Galaxy can be traced by the electromagnetic radiation they produce. Supernova remnants such as the Crab Nebula are known to be a source of cosmic rays. In addition, most cosmic rays are confined to the disk of the Galaxy, presumably by its magnetic field. More HERE
