Generalized Fermi acceleration
Abstract
In highly conducting astrophysical plasmas, charged particles are generically accelerated through Fermitype processes involving repeated interactions with moving magnetized scattering centers. The present paper proposes a generalized description of these acceleration processes, by following the momentum of the particle through a continuous sequence of accelerated frames, defined in such a way that the electric field vanishes at each point along the particle trajectory. In each locally inertial frame, the Lorentz force affects the direction of motion of the particle, but the energy changes solely as a result of inertial corrections. This unified description of Fermi acceleration applies equally well in sub and ultrarelativistic settings, in Cartesian or nonCartesian geometries, flat or nonflat spacetime. Known results are recovered in a variety of regimes—shock, turbulent and shear acceleration—and new results are derived in lieu of applications, e.g., nonresonant acceleration in relativistic turbulence, stochastic unipolar inductive acceleration and centrifugoshear acceleration close to the horizon of a black hole.
 Publication:

Physical Review D
 Pub Date:
 April 2019
 DOI:
 10.1103/PhysRevD.99.083006
 arXiv:
 arXiv:1903.05917
 Bibcode:
 2019PhRvD..99h3006L
 Keywords:

 Astrophysics  High Energy Astrophysical Phenomena;
 Astrophysics  Solar and Stellar Astrophysics;
 Physics  Plasma Physics
 EPrint:
 13 pages, matches published version