Plasma Waves and Cosmic Rays

Theorist Pisin Chen (SLAC and National Taiwan University) and coworkers have recently formed a theory as to how high-energy cosmic ray protons, with energies exceeding 10^20 eV, become so energetic. Current cosmic ray data do not support the notion that these highly energetic particles have some exotic origin, such as the decay of some other unidentified particle, so scientists had been looking at common astrophysical phenomena for possible acceleration mechanisms. However, each of what the article calls the “conventional suggestions,” such as acceleration by relativistic shocks or spinning black holes, has problems accounting for the highest of the proton energies. The theory developed by Chen and his colleagues involves acceleration due to so-called magnetowaves, electromagnetic waves with unusually strong magnetic components in magnetized plasmas, which can drive plasma waves in their wake. Protons riding these plasma waves can, with luck, be accelerated to 10^21 eV. Chen and his coworkers have been able to demonstrate the effects of magnetowaves analytically and using computer simulation, but the conditions for a proton to catch just the right sequence of plasma waves are still extremely rare.

http://blogs.physicstoday.org/update/2009/03/plasma-waves-and-cosmic-rays.html#comments