Departement of Physics, Tokyo Institute of Technology, Japan
Shock waves are ubiquitous in the universe, ranging from familiar shocks ahead of supersonic vehicles, various heliospheric shocks, to largest-scale shocks generated at the cosmological structure formation. According to the dissipation processes at the shock transition regions, these shocks can be classified under two different categories, collisional and collisionless shock waves, the latter of which I will concentrate on. Most importantly, the dissipation processes at collisionless shocks naturally result in the production of large deviation of particle phase space distribution from the thermal equilibrium, namely the acceleration of nonthermal particles. I will review various aspects of collisionless astronomical shocks and relating acceleration phenomena.