Particle acceleration in MHD turbulence

[摘要] MHD Turbulence describes dynamics of astrophysical plasmas on large scale. It is characterized by energy transfer between different scales and the exchange of energy with nonthermal population - typically cosmic rays. Recent progress in theory regarding almost all basic regimes of turbulence - from the dynamo to the decaying case and the asymptotic scaling laws, allowed us to proceed with more observationally motivated questions. One of them is why almost all strongly magnetized environments are indeed observable, e.g. why such environments are infused with high-energy particles, their distributions stretching to energies orders of magnitude higher than thermal. It turns out that there are generic mechanisms of acceleration in turbulence, both second and first order in v/c, the latter was somehow unnoticed. These generic mechanisms may explain the ubiquity of non-thermal tails in various magnetized astrophysical environments, e.g. solar chromosphere, pulsar magnetospheres, jets from supermassive black holes, gamma-ray bursts, etc.

[发布机构] Naval Research Laboratory, Washington; DC; 20375, United States^1

[关键词] Astrophysical plasma;Asymptotic scaling laws;Exchange of energy;High-energy particles;Orders of magnitude;Particle acceleration;Pulsar magnetosphere;Supermassive black holes