Electron beam interaction with space plasmas

Active space experiments involving the controlled injection of electron bea ms and the formation of artificially generated currents can provide in many cases a calibration of natural phenomena connected with the dynamic intera ction of charged particles with fields. They have a long history beginning from the launches of small rockets with electron guns in order to map magne tic fields lines in the Earth's magnetosphere or to excite artificial auror as. Moreover, natural beams of charged particles exist in many space and as trophysical plasmas and were identified in situ by several satellites; a fe w examples are beams connected with solar bursts, planetary foreshocks or s uprathermal fluxes traveling in planetary magnetospheres. Many experimental and theoretical works have been performed in order to int erpret or plan space experiments involving beam injection as well as to und erstand the physics of wave-particle interaction, as wave radiation, beam d ynamics and background plasma modification. Recently, theoretical studies o f the nonlinear evolution of a thin monoenergetic electron beam injected in a magnetized plasma and interacting with a whistler wave packet have led t o new results. The influence of an effective dissipation process connected with whistler wave field leakage out of the beam volume to infinity (that i s, effective radiation outside the beam) on the nonlinear evolution of beam electrons distribution in phase space has been studied under conditions re levant to active space experiments and related laboratory modelling. The be am-waves system's evolution reveals the formation of stable nonlinear struc tures continuously decelerated due to the effective friction imposed by the strongly dissipated waves. The nonlinear interaction between the electron bunches and the wave packet are discussed in terms of dynamic energy exchan ge, particle trapping, slowing down of the beam, wave dissipation and quasi -linear diffusion.