Accélération de protons dans les Restes de Supernova – ACCELRSN

Since their discovery by Hess (1912), the understanding of the origin of Galactic cosmic rays remains a recalcitrant problem. It raises a number of questions related to the origin of the energy, the acceleration mechanism at work, the maximum energy and spectral form produced by this mechanism and the number of required types of accelerator. Can a unique type of sources and acceleration mechanism account for the observations ? The only theory of particle acceleration sufficiently developed to allow quantitative calculations and to meet many of the observational constraints is the diffusive acceleration applied to the strong shocks associated with supernova remnants. The maturity of these models and their confrontation to the new high energy observations allow to retrieve physical parameters of the acceleration mechanism, and specifically the fraction of accelerated protons. This is one of the key question in this field. The project has two main objectives: - to derive consistently these parameters, by the fitting of the entire wavelength spectrum (thermal and non-thermal) with semi-analytical cosmic-ray modified hydrodynamical models, which include the various physical processes relevant for supernova remnant experiencing particle acceleration. - to develop numerical simulations of SNRs including the back-reaction of accelerated protons on the hydrodynamics. The originality of our approach consists in : - constraining the models by the fitting of the entire electromagnetic spectrum (thermal and non-thermal) from radio to TeV gamma-rays. We will combine observations from all the available high energy experiments (XMM-Newton, INTEGRAL, HESS and in the near future GLAST, and then HESS II). These various experiments cover all the radiation processes related to shock heating and particle acceleration at the shock, and specifically the acceleration of protons with GLAST and HESS II. - using and developing cosmic-ray modified semi-analytical models of supernova remnants, which couple the properties of the thermal plasma to those of the relativistic plasma. Recent observations of young supernova remnants have demonstrated that particle (ion) acceleration at their shock is energetically important, as there is a direct impact on the morphology and characteristics of the thermal gas. It is thus necessary to take into account this coupling in the models and to fit the data over the entire wavelength spectrum, including the thermal and non-thermal radiations. - developing 3-D models of supernova remnants by including the back-reaction of particle acceleration in 3-D hydrodynamical simulations (RAMSES), as well as the relevant physical processes. We will quantify the bias introduced by a simple (but adjustable) modelling on the determination of the physical parameters related to the acceleration mechanism at work. We will determine the morphological signature of accelerated protons taking into account the development of Rayleigh-Taylor instabilities and produce specific models dedicated to supernova remnants, prototype of proton accelerators. The currently working high energy telescopes are providing exceptional data on supernova remnants, completely new in the TeV regime. These observations provide new perspectives and key diagnostics for the understanding of particle acceleration in these objects. France, deeply involved in these experiments, lacks however representation in this thematic. New experiments are already in development in this domain and will offer soon important results. Our project has for objective to strengthen, in our laboratory and more generally in France, the field of supernova remnants, and especially that of particle acceleration at their shock.