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Title: The transport of cosmic rays across magnetic fieldlines

Abstract

The long residence times and small anisotropies of cosmic rays suggest that they are well confined and well scattered by the Galactic magnetic field. Due to the disk-like shape of the confinement volume, transport in the vertical direction, which is perpendicular to the mean Galactic magnetic field, is key to cosmic ray escape. It has long been recognized that this vertical transport depends both on the vertical component of the field lines themselves and on the extent to which the cosmic rays are tied to the field lines. In this paper, we use magnetic fields with very simple spatial and temporal structures to isolate some important features of cross field line transport. We show that even simple magnetic nonuniformities combined with pitch angle scattering can enhance cross field line transport by several orders of magnitude, while pitch angle scattering is unnecessary for enhanced transport if the field is chaotic. Nevertheless, perpendicular transport is much less than parallel transport in all the cases we study. We apply the results to confinement of cosmic rays in the Fermi bubbles.

Authors:
 [1];  [2]
  1. Wisconsin IceCube Particle Astrophysics Center (WIPAC) and Department of Astronomy, University of Wisconsin-Madison, 222 West Washington Avenue, Madison, WI 53703 (United States)
  2. Departments of Astronomy and Physics, Center for Magnetic Self-Organization, University of Wisconsin-Madison, 475 North Charter Street, Madison, WI 53706 (United States)
Publication Date:
OSTI Identifier:
22365373
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 791; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ANISOTROPY; CHAOS THEORY; COMPUTERIZED SIMULATION; COSMIC RADIATION; GALAXIES; INCLINATION; MAGNETIC FIELDS; SCATTERING

Citation Formats

Desiati, Paolo, and Zweibel, Ellen G., E-mail: desiati@wipac.wisc.edu, E-mail: zweibel@astro.wisc.edu. The transport of cosmic rays across magnetic fieldlines. United States: N. p., 2014. Web. doi:10.1088/0004-637X/791/1/51.
Desiati, Paolo, & Zweibel, Ellen G., E-mail: desiati@wipac.wisc.edu, E-mail: zweibel@astro.wisc.edu. The transport of cosmic rays across magnetic fieldlines. United States. doi:10.1088/0004-637X/791/1/51.
Desiati, Paolo, and Zweibel, Ellen G., E-mail: desiati@wipac.wisc.edu, E-mail: zweibel@astro.wisc.edu. Sun . "The transport of cosmic rays across magnetic fieldlines". United States. doi:10.1088/0004-637X/791/1/51.
@article{osti_22365373,
title = {The transport of cosmic rays across magnetic fieldlines},
author = {Desiati, Paolo and Zweibel, Ellen G., E-mail: desiati@wipac.wisc.edu, E-mail: zweibel@astro.wisc.edu},
abstractNote = {The long residence times and small anisotropies of cosmic rays suggest that they are well confined and well scattered by the Galactic magnetic field. Due to the disk-like shape of the confinement volume, transport in the vertical direction, which is perpendicular to the mean Galactic magnetic field, is key to cosmic ray escape. It has long been recognized that this vertical transport depends both on the vertical component of the field lines themselves and on the extent to which the cosmic rays are tied to the field lines. In this paper, we use magnetic fields with very simple spatial and temporal structures to isolate some important features of cross field line transport. We show that even simple magnetic nonuniformities combined with pitch angle scattering can enhance cross field line transport by several orders of magnitude, while pitch angle scattering is unnecessary for enhanced transport if the field is chaotic. Nevertheless, perpendicular transport is much less than parallel transport in all the cases we study. We apply the results to confinement of cosmic rays in the Fermi bubbles.},
doi = {10.1088/0004-637X/791/1/51},
journal = {Astrophysical Journal},
number = 1,
volume = 791,
place = {United States},
year = {Sun Aug 10 00:00:00 EDT 2014},
month = {Sun Aug 10 00:00:00 EDT 2014}
}
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