THE EFFECT OF DRIFT ON THE EVOLUTION OF THE ELECTRON/POSITRON SPECTRA IN AN AXISYMMETRIC PULSAR WIND NEBULA

Charged particles propagating through a structured magnetic field are subject to drift motion. The primary aim of the present paper is therefore to investigate the effects of gradient, curvature, and neutral sheet drift on the evolution of the electron and positron spectra in a pulsar wind nebula, w...

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Bibliographic Details
Published inThe Astrophysical journal Vol. 788; no. 2; pp. 132 - 9
Main Authors Vorster, Michael J., Moraal, Harm
Format Journal Article
LanguageEnglish
Published United States 20.06.2014
Subjects
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
AXIAL SYMMETRY
Axisymmetric
CHARGED PARTICLES
DIFFUSION
Drift
ELECTRONS
ENERGY LOSSES
Evolution
FOKKER-PLANCK EQUATION
MAGNETIC FIELDS
NEBULAE
Neutral sheets
Positrons
PULSARS
SPECTRA
STEADY-STATE CONDITIONS
STELLAR WINDS
SUPERNOVA REMNANTS
SYNCHROTRON RADIATION
TRANSPORT THEORY
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Summary:Charged particles propagating through a structured magnetic field are subject to drift motion. The primary aim of the present paper is therefore to investigate the effects of gradient, curvature, and neutral sheet drift on the evolution of the electron and positron spectra in a pulsar wind nebula, where the drift motion is a direct result of the magnetic field having an Archimedean spiral structure. In order to investigate the evolution of the spectra, the steady-state, axisymmetric Fokker-Planck transport equation is solved numerically using a finite-difference scheme. Apart from drift motion, the transport processes of convection and diffusion, along with the energy loss processes of adiabatic cooling and synchrotron radiation, are also included in the model. It is found that drift, particularly neutral sheet drift, can lead to a quantitative difference in the evolution of the electron and positron spectra. This difference may be of importance when interpreting the positron excess observed by PAMELA and AMS-02 near Earth.
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ISSN:0004-637X
1538-4357
DOI:10.1088/0004-637X/788/2/132