The amplification of magnetic fields in parallel shocks

The amplification of magnetic fields due to plasma instabilities in various energetic environments is a crucial issue for our understanding of particle acceleration and the observed emission from these regions. This process is supported both by observations of large magnetic fields close to the outer shocks of supernova remnants and also by the theoretical motivation to explain the origin of galactic cosmic rays. The so-called non-resonant current driven instability seems to be a likely mechanism capable of driving such strong amplification. The role of this instability in various environments is reviewed, and recent results from numerical simulations are presented