Journal Article10.1086/168837
Particle Acceleration in Step Function Shear Flows: A Microscopic Analysis
J. R. Jokipii,Gregor E. Morfill +1 more
31
TL;DR: In this article, a Monte Carlo analysis of particle motion in a moving, scattering fluid is presented, and it is shown that particles gain energy at a rate proportional to the square of the magnitude of the velocity change.
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Abstract: The transport of energetic particles in a moving, scattering fluid, which has a large shear in its velocity over a distance small compared with the scattering mean free path is discussed. The analysis is complementary to an earlier paper by Earl, Jokipii, and Morfill (1988), which considered effects of more-gradual shear in the diffusion approximation. The case in which the scattering fluid undergoes a step function change in velocity, in the direction normal to the flow is considered. An analytical, approximate calculation and a Monte Carlo analysis of particle motion are presented. It is found that particles gain energy at a rate proportional to the square of the magnitude of the velocity change.
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Citations
Fermi acceleration in astrophysical jets
TL;DR: In this article, the acceleration of charged particles by Fermi processes (i.e., diffusive shock acceleration, second order FermI acceleration, and gradual shear acceleration) in relativistic astrophysical jets is considered.
142
Shear Acceleration in Relativistic Astrophysical Jets
Frank M. Rieger,Peter Duffy +1 more
TL;DR: In this article, the acceleration of energetic particles by a velocity shear in the relativistic background flow containing scattering centers is considered. And three possible acceleration sites for astrophysical jets are identified: (1) a velocity profile decreasing linearly outward with radial coordinates, (2) gradual velocity shears perpendicular to the jet axis, such as intrinsic jet rotation, and (3) nongradual and/or discontinuous longitudinal velocities at the jet-side boundary.
139
Particle Acceleration in Mildly Relativistic Shearing Flows: The Interplay of Systematic and Stochastic Effects, and the Origin of the Extended High-energy Emission in AGN Jets
TL;DR: In this paper, the authors investigate the potential of shearing flows to facilitate an extended acceleration of particles and evaluate its impact on the resultant particle distribution, and show that for typical parameters applicable to large-scale AGN jets, stochastic second-order Fermi acceleration, which always accompanies shear particle acceleration, can play an important role in facilitating the whole process of particle energization.
69
An Introduction to Particle Acceleration in Shearing Flows
Frank M. Rieger
- 10 Sep 2019
TL;DR: The acceleration of charged particles by microscopic instabilities in collisionless relativistic shear flows, Fermi-type particle acceleration in macroscopic, gradual and non-gradual shear flow, as well as shear particle acceleration by large-scale velocity turbulence are discussed in this article.
62
Generalized Fermi acceleration
TL;DR: In this paper, a generalized description of Fermi acceleration processes is proposed, 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.
57