Title: Magnetic Reconnection: A Powerful Cosmic Particle Accelerator
Speaker: Fan Guo (Los Alamos National Laboratory)
Time: 16:00pm, Nov. 5 (Thursday)
Location: https://zoom.com.cn/j/5576839595 ID: 557 683 9595
Abstract: Astrophysical sites of magnetic reconnection have long been expected to be sources of high-energy particles and radiation. Recent observations of high-energy astrophysical sources as well as solar flares have motivated us to better understand magnetic reconnection and its associated particle acceleration in plasma conditions where the magnetic energy is dominant. I will present fully kinetic particle-in-cell simulations of anti-parallel magnetic reconnection in the highly magnetized regime (magnetization parameter much higher than unity and plasma beta much less than unity). We find that the magnetic energy is efficiently converted into kinetic energy of nonthermal relativistic particles in a power-law spectrum in both two-dimensional and three-dimensional simulations. For a sufficiently large system and strong magnetic field, the power-law index approaches “-1”. We have now demonstrated, through a combination of advanced diagnostics and theoretical analysis, that the dominant acceleration mechanism is a Fermi-like process accomplished through the curvature drift motion of particles in magnetic flux tubes along the electric field induced by fast plasma flows. I will present an analytical model for the formation of power-law distribution and show the nonthermal distribution may be a common feature of magnetically dominated reconnection. I will also discuss a large-scale reconnection acceleration model that includes physics derived from particle-in-cell simulations and present some of its preliminary application to solar flare particle acceleration.