Étude de l'accélération des rayons cosmiques par les ondes de choc des restes de supernovae dans les superbulles galactiques

摘要

In this thesis we study the acceleration of cosmic-rays, high-energy particles pervading the Universe. Galactic cosmic-rays are believed to be produced by diffusive shock acceleration in supernovae remnants. The linear theory explains the formation of power-law spectra, but it has to be amended because of the back-reaction of cosmic-rays. We focus our attention on repeated acceleration by successive shocks, which hardens the spectra, and relies on the transport of cosmic-rays between the shocks.For this study we have developped a numerical tool which couples the hydrodynamical evolution of the plasma with the kinetic transport of the cosmic-rays. We have validated it against previous results. To resolve all the space- and time-scales induced by the energy-dependent diffusion of cosmic-rays we have implemented an adaptive mesh refinement technique. To save more computational power we have also parallelized our code, in the energy dimension. This enables us to present the first numerical simulations of non-linear acceleration by multiple shocks.We apply our tool to superbubbles, the big hot tenuous structures surrounding OB associations, as this is probably the place where most supernovae explode -- leading to substantial modifications of the standard model of the production of Galactic cosmic-rays. More precisely we have begun to investigate the effects of multiple shocks, through studying the role of pre-existing cosmic-rays upstream of a blast wave. Finally we review the radiation from superbubbles with a view to efficient cosmic-ray production.