| Abstract |
The mechanisms that accelerate cosmic relativistic particles are not
fully understood yet. A variety of processes has been investigated and
the acceleration in magnetic reconnection sites has lately gained
increasing attention from researchers not only for its potential
importance in the solar system, but also beyond it, in astrophysical
environments like compact stellar sources, AGNs and GRBs, and even in
diffusive magnetized media as the interstellar medium (ISM) and the
intergalactic medium (IGM). In this talk we review this process and,
supported by three-dimensional MHD simulations with the injection of
thousands of test particles, we show that they can be efficiently
accelerated by magnetic reconnection through a first-order Fermi process
within large scale magnetic current sheets, even in a collisional fluid
(contrary to what was previously believed), especially when local
turbulence is present which makes reconnection fast, the acceleration
layer thicker and the overall process naturally three-dimensional.
Tests of particle acceleration in pure MHD turbulent environments (i.e.,
without the presence of large scale current sheets), on the other hand,
indicate that the dominant acceleration process is a second-order Fermi. |