Cluster observations of shock front nonstationarity and its consequences for particle dynamics.

One of the aims of the Cluster Short Separation at the Bow Shock campaign aimed to investigate the process of non stationarity of the quasi-perpendicular shock front. During this campaign a spacecraft separation only a few kilometres was achieved in hte vicinity of the terrestrial bow shock. The measurements obtained were consistent with the Gradient Catastrophe type model (GC) of ramp non stationarity. The results of the Short Separation at the Bow Shock Cluster campaign are presented. The implications of GC type non stationarity on the evolution of particle distributions at the shock front and pick up ions are discussed.