Interplanetary Shock Waves in the Earth Magnetosheath: Cluster Observations

Shock waves collisions are a basic problem in plasma physics and play an important role in many processes occurring in space. In particular, the impacts of the interplanetary shock waves (IPS) on the terrestrial bow shock are relevant to the Space Weather. In fact, understanding how the associated pressure pulses in magnetosheath are shaped after these impacts, can help to model in a more realistic way the perturbed magnetosphere and to gain a deeper knowledge into the fundamental mechanisms causing the geomagnetic activity. Here we present an event, seen by Cluster spacecraft, showing the complex and non-linear nature of the phenomenon. Actually the associated variations in plasma parameters and in the magnetic field are due, besides the transmitted interplanetary shocks, to other secondary (i.e. produced in the impact) discontinuities and waves.