Title : Relativistic Nonthermal Particle Acceleration in 2D Plasmoid-Dominated Magnetic Reconnection
Speaker Name: Dmitri Uzdensky Speaker Institution : University of Colorado, Boulder
Abstract : Relativistic magnetic reconnection is commonly believed to be an efficient mechanism for accelerating relativistic particles, thus offering an attractive explanation for nonthermal high-energy emission from many astrophysical sources. This view is strongly supported by solid and ample numerical evidence, mostly from first-principles kinetic plasma simulations, whereas our theoretical understanding of reconnection-driven nonthermal particle acceleration (NTPA) remains incomplete. In this talk I will first overview the recent numerical progress on this problem, and then will outline a conceptual analytical model aimed at elucidating key physical processes that power NTPA in 2D hierarchical reconnecting plasmoid chains. In this model, the main reconnection electric field, the 1st-order Fermi/curvature-drift acceleration in contracting plasmoids, and Fermi-type energy gain due to particle reflection off moving plasmoids all contribute to particle acceleration, while particle trapping inside plasmoids plays the role of escape and governs the high-energy cutoff, thus tying the particle spectrum to the plasmoid distribution.