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Title: The Acceleration of Charged Particles at a Spherical Shock Moving through an Irregular Magnetic Field

Abstract

We investigate the physics of charged-particle acceleration at spherical shocks moving into a uniform plasma containing a turbulent magnetic field with a uniform mean. This has applications to particle acceleration at astrophysical shocks, most notably, to supernovae blast waves. We numerically integrate the equations of motion of a large number of test protons moving under the influence of electric and magnetic fields determined from a kinematically defined plasma flow associated with a radially propagating blast wave. Distribution functions are determined from the positions and velocities of the protons. The unshocked plasma contains a magnetic field with a uniform mean and an irregular component having a Kolmogorov-like power spectrum. The field inside the blast wave is determined from Maxwell’s equations. The angle between the average magnetic field and unit normal to the shock varies with position along its surface. It is quasi-perpendicular to the unit normal near the sphere’s equator, and quasi-parallel to it near the poles. We find that the highest intensities of particles, accelerated by the shock, are at the poles of the blast wave. The particles “collect” at the poles as they approximately adhere to magnetic field lines that move poleward from their initial encounter with the shockmore » at the equator, as the shock expands. The field lines at the poles have been connected to the shock the longest. We also find that the highest-energy protons are initially accelerated near the equator or near the quasi-perpendicular portion of the shock, where the acceleration is more rapid.« less

Authors:
 [1]
  1. Department of Planetary Sciences, University of Arizona, Tucson, AZ (United States)
Publication Date:
OSTI Identifier:
22679733
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 848; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ACCELERATION; APPROXIMATIONS; ASTROPHYSICS; CHARGED PARTICLES; DISTRIBUTION; DISTRIBUTION FUNCTIONS; EQUATIONS OF MOTION; EXPLOSIONS; HELIOSPHERE; MAGNETIC FIELDS; PLASMA; PROTONS; SHOCK WAVES; SPECTRA; SUPERNOVA REMNANTS; SUPERNOVAE; SURFACES; TURBULENCE; VELOCITY

Citation Formats

Giacalone, J. The Acceleration of Charged Particles at a Spherical Shock Moving through an Irregular Magnetic Field. United States: N. p., 2017. Web. doi:10.3847/1538-4357/AA8DF1.
Giacalone, J. The Acceleration of Charged Particles at a Spherical Shock Moving through an Irregular Magnetic Field. United States. doi:10.3847/1538-4357/AA8DF1.
Giacalone, J. Fri . "The Acceleration of Charged Particles at a Spherical Shock Moving through an Irregular Magnetic Field". United States. doi:10.3847/1538-4357/AA8DF1.
@article{osti_22679733,
title = {The Acceleration of Charged Particles at a Spherical Shock Moving through an Irregular Magnetic Field},
author = {Giacalone, J.},
abstractNote = {We investigate the physics of charged-particle acceleration at spherical shocks moving into a uniform plasma containing a turbulent magnetic field with a uniform mean. This has applications to particle acceleration at astrophysical shocks, most notably, to supernovae blast waves. We numerically integrate the equations of motion of a large number of test protons moving under the influence of electric and magnetic fields determined from a kinematically defined plasma flow associated with a radially propagating blast wave. Distribution functions are determined from the positions and velocities of the protons. The unshocked plasma contains a magnetic field with a uniform mean and an irregular component having a Kolmogorov-like power spectrum. The field inside the blast wave is determined from Maxwell’s equations. The angle between the average magnetic field and unit normal to the shock varies with position along its surface. It is quasi-perpendicular to the unit normal near the sphere’s equator, and quasi-parallel to it near the poles. We find that the highest intensities of particles, accelerated by the shock, are at the poles of the blast wave. The particles “collect” at the poles as they approximately adhere to magnetic field lines that move poleward from their initial encounter with the shock at the equator, as the shock expands. The field lines at the poles have been connected to the shock the longest. We also find that the highest-energy protons are initially accelerated near the equator or near the quasi-perpendicular portion of the shock, where the acceleration is more rapid.},
doi = {10.3847/1538-4357/AA8DF1},
journal = {Astrophysical Journal},
issn = {0004-637X},
number = 2,
volume = 848,
place = {United States},
year = {2017},
month = {10}
}