  The collisionless interaction of an expanding high-energy plasma cloud with a
magnetized background plasma in the presence of a dipole magnetic field is
examined in the framework of a 2D3V hybrid (kinetic ions and massless fluid
electrons) model. The retardation of the plasma cloud and the dynamics of the
perturbed electromagnetic fields and the background plasma are studied for high
Alfven-Mach numbers using the particle-in-cell method. It is shown that the
plasma cloud expands excluding the ambient magnetic field and the background
plasma to form a diamagnetic cavity which is accompanied by the generation of a
collisionless shock wave. The energy exchange between the plasma cloud and the
background plasma is also studied and qualitative agreement with the analytical
model suggested previously is obtained.
