Powered by Indico
v3.2
Abstract: Energetic particles are ubiquitous in the interplanetary space; ground based and spacecraft observations have detected cosmic rays coming from galactic and extragalactic sources, energetic particles accelerated at impulsive events in the solar corona and at interplanetary shocks. However, the acceleration mechanisms are not fully understood, yet. The Sun is the most powerful accelerator of particles with energies less than 1 GeV. Those particles are detected near the Earth as solar energetic particles (SEPs). Fluctuations in SEPs fluxes are related to solar activity and to magnetic turbulence in the interplanetary medium. They represent a hazard for the functioning of commercial and scientific satellites, so that the reliable prediction of high SEP fluxes is one of the main objectives of the space weather.
In this Colloquium, the transport properties of supra-thermal particles accelerated over a variety of interplanetary shock waves will be revised, as inferred from the analysis of particle fluxes, addressing that anomalous, superdiffusive transport is common in the interplanetary medium.
Thanks to in-situ observations it has been possible to make a complete determination of the parameters of the superdiffusive transport, such as the superdiffusive coefficient, the energy spectral index, the typical acceleration time. The diagnostic developed for energetic particle fluxes in the interplanetary space has been extended to the study of the X-ray emission profiles of relativistic electrons accelerated at the blast waves of some historical supernova remnants, and some applications have also been made for relativistic electrons accelerated at low Mach number shocks in galaxy clusters.
An overview of the occurrence of superdiffusion in astrophysical plasmas will be given also in relation with results coming from numerical experiments and some considerations will be addressed in light of the new space missions Parker Solar Probe (in operation) and Solar Orbiter (upcoming).