Speaker: Martin Lemoine , Institut d’Astrophysique de Paris, CNRS
Abstract: How magnetized turbulent plasmas can accelerate charged
particles to high energies represents a long-standing question with
far-reaching implications for high-energy and multi-messenger
astrophysics. It indeed goes back to the seminal works of Enrico Fermi (1949, 1954) and nowadays, it is commonly invoked to model the
generation of non-thermal particle spectra in a broad variety of
astrophysical sites, including extreme, relativistic sources. In
particular, it has recently been considered as a possible origin for the high-energy neutrinos seen by Ice Cube in the direction of nearby active galactic nuclei.
Our understanding of particle acceleration in turbulent plasmas has
known substantial progress in recent years, mostly spurred by
large-scale, kinetic numerical simulations. This talk will address those developments and discuss a theoretical picture to describe the physics at play, based on non-resonant interactions between particles and velocity structures. This model, which can be seen as a modern implementation of the original Fermi scenario, appears supported by recent numerical simulations of turbulence in the semi- and fully-relativistic regime. It also brings to light an interesting connection between the properties of intermittency of the turbulence and the spectrum of accelerated particles. I will discuss those features then conclude with some possible applications and extensions.