Distributions of particles accelerated by strong Alfvénic turbulence

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Main Authors: Boldyrev, Stanislav, Humphrey, Daniel, Roytershteyn, Vadim
Format: Preprint
Published: 2026
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author Boldyrev, Stanislav
Humphrey, Daniel
Roytershteyn, Vadim
author_facet Boldyrev, Stanislav
Humphrey, Daniel
Roytershteyn, Vadim
contents This work presents a model for generating nonthermal power-law tails of particles' energy probability density functions in turbulent collisionless plasmas, applicable to both non-relativistic and relativistic scenarios. We propose that strong Alfvénic turbulence energizes plasma particles through curvature acceleration, particularly for particles with Larmor radii comparable to the scales of turbulence. When the energy density of the energized particles increases, the efficiency of the energy exchange process diminishes. As a result, the acceleration process saturates, leading to power-law distributions of particle momentum and energy. In the non-relativistic case, the momentum probability density function scales as $f(p) dp \propto p^{-3} dp $, while in the ultrarelativistic case, the energy probability density function scales as $ f(γ) dγ\propto γ^{-3} dγ$. This model provides a unified framework for understanding particle acceleration in both energy regimes, complementing existing analytical approaches. Its predictions are consistent with available observations of energetic ion distributions in the heliosphere and with the findings from numerical simulations of ultrarelativistic particle acceleration in magnetically dominated plasma turbulence.
format Preprint
id arxiv_https___arxiv_org_abs_2605_02219
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Distributions of particles accelerated by strong Alfvénic turbulence
Boldyrev, Stanislav
Humphrey, Daniel
Roytershteyn, Vadim
Plasma Physics
High Energy Astrophysical Phenomena
This work presents a model for generating nonthermal power-law tails of particles' energy probability density functions in turbulent collisionless plasmas, applicable to both non-relativistic and relativistic scenarios. We propose that strong Alfvénic turbulence energizes plasma particles through curvature acceleration, particularly for particles with Larmor radii comparable to the scales of turbulence. When the energy density of the energized particles increases, the efficiency of the energy exchange process diminishes. As a result, the acceleration process saturates, leading to power-law distributions of particle momentum and energy. In the non-relativistic case, the momentum probability density function scales as $f(p) dp \propto p^{-3} dp $, while in the ultrarelativistic case, the energy probability density function scales as $ f(γ) dγ\propto γ^{-3} dγ$. This model provides a unified framework for understanding particle acceleration in both energy regimes, complementing existing analytical approaches. Its predictions are consistent with available observations of energetic ion distributions in the heliosphere and with the findings from numerical simulations of ultrarelativistic particle acceleration in magnetically dominated plasma turbulence.
title Distributions of particles accelerated by strong Alfvénic turbulence
topic Plasma Physics
High Energy Astrophysical Phenomena
url https://arxiv.org/abs/2605.02219