Non-linear Cosmic Ray acceleration in Supernova Remnants

[Excerpt from a 9 pages abstract]: Long time has passed since 1912, when some balloon experiments of the Austrian physicist Victor Hess found that natural radioactivity increases again above 600 m from the ground, despite the larger distance from the radioactive elements in the Earth crust. For the first time an unknown, extraterrestrial, source of radiation usually shielded by the atmosphere had been observed. ...