Relativistic astrophysics with relativistic beams

The possibility of producing intense relativistic beams also opens the way to the exploration of relativistic astrophysical scenarios. The radiation from pulsars, gamma ray bursts and blazar jets is associated with relativistic e-beams. Experiments using relativistic beams in a laboratory plasma may be able to shed light on the key radiation processes. Moreover, in gamma ray bursts, electron-positron-proton streaming instabilities are unstable to the Weibel instability. This generates B fields, which in turn lead to the synchrotron radiation features observed in these most extreme explosions of the Universe.

Experiments with relativistic streams can not only provide information about the magnetic fields generated by these streams as relativistic shocks form, and their long time evolution, but also about the mechanisms for particle acceleration through collective plasma mechanisms (e.g. plasma wakefield acceleration) and radiation generation in the tangled magnetic field structure. Such scenarios are also common in blazar jets, where the radiation is generated by e-beams moving into high b field regions resulting in maser emission and similarly with pulsars where e-beams are thought to be unstable to streaming instabilities. The production of gamma rays and positrons can also be studied using relativistic e-beams or colliding plasma configurations, as well as the creation of laboratory neutron star atmospheres (with ultra intense B-fields) and photon bubbles. The possibility to examine the formation of collisionless shocks is also of paramount importance. The generated relativistic streams of particles in HiPER scenarios can lead to the onset of nonlinear structures that will evolve to high Mach number collisionless shocks. Collisionless shocks are pervasive in astrophysics, and the possibility to examine in detail how particles are accelerated in these structures can provide answers to how particles/cosmic rays are accelerated in the Universe.