Princeton Plasma Physics Laboratory (PPPL) Theory Seminar - ADDED

Nonthermal particles are ubiquitous in astrophysical plasmas, and explosive phenomena such as supernova remnant shocks and solar flares have demonstrated evidence for the production of relativistic high-energy particles. Yet the particle acceleration mechanism remains an unresolved issue. Historically, after the idea of the stochastic acceleration by Enrico Fermi in 1949, many acceleration models have been proposed to explain nonthermal cosmic ray particles, and the diffusive shock acceleration is believed to be primary mechanism by which particles gain nonthermal energies through stochastic scattering between the shock upstream and downstream. However, recent modern observations suggest that the diffusive shock acceleration alone cannot explain the observed cosmic ray particles, and other acceleration mechanisms with much efficient production of the nonthermal particle are needed. We present supercomputer simulations showing that efficient electron energization can occur during turbulent magnetic reconnection arising from a strong collisionless shock. Upstream electrons undergo first-order Fermi acceleration by colliding with reconnection jets and magnetic islands, giving rise to a nonthermal relativistic population downstream. These results may shed new light on magnetic reconnection as an agent of energy dissipation and particle acceleration in strong shock waves.