Galactic cosmic rays

In this brief review we describe the theory of the origin of Galactic cosmic rays. The concept that interaction near the source is the dominant source of γ-rays, and spallation secondaries seems best suited to explain the EGRET γ-spectrum of the inner Galaxy, the abundances of light elements, the anti-protons and the positrons. Also the chemical abundances seem best described as resulting from the chemical composition of massive star winds. This leads to a supernova mechanism, long known, that the magneto-rotational mechanism provides the energy, about 10 erg, for the explosion of the most massive stars; this mechanism naturally allows to understand jet-supernovae and Gamma Ray Bursts from its underlying symmetry. A key theoretical question remains open: the role of magnetic fields, both in the transport of cosmic rays in the Galaxy, as well as in the enhancement they may get in shock waves on various length scales, either starting with existing magnetic fields, or starting from electric current systems. An ultimate hope and expectation obviously is, once we understand the origin and physics of cosmic rays, to turn them into a tool to understand to understand the nature of matter at a yet deeper level.