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Ion pre-acceleration in fully self-consistent particle-in-cell simulations of supercritical perpendicular reforming shocks in multiple ion species plasmas
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Rekaa, V. L., Chapman, Sandra C. and Dendy, R. O. (2014) Ion pre-acceleration in fully self-consistent particle-in-cell simulations of supercritical perpendicular reforming shocks in multiple ion species plasmas. The Astrophysical Journal, Volume 791 (Number 1). pp. 26-34. doi:10.1088/0004-637X/791/1/26 ISSN 0004-637X.
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Official URL: http://dx.doi.org/10.1088/0004-637X/791/1/26
Abstract
Supernova remnant and heliopause termination shock plasmas may contain significant populations of minority heavy ions, with relative number densities n α/ni up to 50%. Preliminary kinetic simulations of collisionless shocks in these environments showed that the reformation cycle and acceleration mechanisms at quasi-perpendicular shocks can depend on the value of n α/ni . Shock reformation unfolds on ion spatio-temporal scales, requiring fully kinetic simulations of particle dynamics, together with the self-consistent electric and magnetic fields. This paper presents the first set of particle-in-cell simulations for two ion species, protons (np ) and α-particles (n α), with differing mass and charge-to-mass ratios, that spans the entire range of n α/ni from 0% to 100%. The interplay between the differing gyro length scales and timescales of the ion species is crucial to the time-evolving phenomenology of the shocks, the downstream turbulence, and the particle acceleration at different n α/ni . We show how the overall energization changes with n α/ni , and relate this to the processes individual ions undergo in the shock region and in the downstream turbulence, and to the power spectra of magnetic field fluctuations. The crossover between shocks dominated by the respective ion species happens when n α/ni = 25%, and minority ion energization is strongest in this regime. Energization of the majority ion species scales with injection energy. The power spectrum of the downstream turbulence includes peaks at sequential ion cyclotron harmonics, suggestive of ion ring-beam collective instability.
Item Type: | Journal Article | ||||||||
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Subjects: | Q Science > QB Astronomy | ||||||||
Divisions: | Faculty of Science, Engineering and Medicine > Science > Physics | ||||||||
Library of Congress Subject Headings (LCSH): | Shock waves, Supernova remnants, Ions -- Mathematical models, Cosmic rays | ||||||||
Journal or Publication Title: | The Astrophysical Journal | ||||||||
Publisher: | Institute of Physics Publishing, Inc. | ||||||||
ISSN: | 0004-637X | ||||||||
Official Date: | 23 July 2014 | ||||||||
Dates: |
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Volume: | Volume 791 | ||||||||
Number: | Number 1 | ||||||||
Page Range: | pp. 26-34 | ||||||||
DOI: | 10.1088/0004-637X/791/1/26 | ||||||||
Status: | Peer Reviewed | ||||||||
Publication Status: | Published | ||||||||
Access rights to Published version: | Restricted or Subscription Access | ||||||||
Date of first compliant deposit: | 27 December 2015 | ||||||||
Date of first compliant Open Access: | 27 December 2015 | ||||||||
Funder: | Norges forskningsråd [Norwegian Research Council], Engineering and Physical Sciences Research Council (EPSRC), Commission of the European Communities | ||||||||
Grant number: | EP/G003955 (EPSRC), EP/G054940/1 (EPSRC), EP/G055165/1 (EPSRC), and EP/G056803/1 (EPSRC) |
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