Numerical investigation of auroral cyclotron maser processes

David Speirs, K. Ronald, S. L. McConville, K. M. Gillespie, A. D. R. Phelps, A. W. Cross, R. Bingham, C. W. Robertson, Colin Whyte, W. He, I. Vorgul, R. A. Cairns, B. J. Kellett

Research output: Contribution to journalArticle

24 Citations (Scopus)

Abstract

When a mainly rectilinear electron beam is subject to significant magnetic compression, conservation of magnetic moment results in the formation of a horseshoe shaped velocity distribution. It has been shown that such a distribution is unstable to cyclotron emission and may be responsible for the generation of auroral kilometric radiation-an intense rf emission sourced at high altitudes in the terrestrial auroral magnetosphere. Particle-in-cell code simulations have been undertaken to investigate the dynamics of the cyclotron emission process in the absence of cavity boundaries with particular consideration of the spatial growth rate, spectral output and rf conversion efficiency. Computations reveal that a well-defined cyclotron emission process occurs albeit with a low spatial growth rate compared with waveguide bounded simulations. The rf output is near perpendicular to the electron beam with a slight backward-wave character reflected in the spectral output with a well defined peak at 2.68 GHz, just below the relativistic electron cyclotron frequency. The corresponding rf conversion efficiency of 1.1% is comparable to waveguide bounded simulations and consistent with the predictions of kinetic theory that suggest efficient, spectrally well defined emission can be obtained from an electron horseshoe distribution in the absence of radiation boundaries.

LanguageEnglish
Article number056501
Number of pages8
JournalPhysics of Plasmas
Volume17
Issue number5
DOIs
Publication statusPublished - 5 May 2010

Fingerprint

masers
cyclotrons
output
magnetic compression
electron beams
waveguides
backward waves
simulation
cyclotron frequency
radiation
high altitude
kinetic theory
magnetospheres
conservation
electrons
velocity distribution
magnetic moments
cavities
predictions

Keywords

  • aurora
  • cyclotron masers
  • electron beams
  • magnetosphere
  • plasma kinetic theory
  • plasma simulation
  • plasma-beam interactions
  • terrestrial kilometric radiation
  • plasma cavities
  • wave modes
  • particle emission
  • solar wind
  • electromagnetic radiation

Cite this

Speirs, David ; Ronald, K. ; McConville, S. L. ; Gillespie, K. M. ; Phelps, A. D. R. ; Cross, A. W. ; Bingham, R. ; Robertson, C. W. ; Whyte, Colin ; He, W. ; Vorgul, I. ; Cairns, R. A. ; Kellett, B. J. / Numerical investigation of auroral cyclotron maser processes. In: Physics of Plasmas. 2010 ; Vol. 17, No. 5.
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Numerical investigation of auroral cyclotron maser processes. / Speirs, David; Ronald, K.; McConville, S. L.; Gillespie, K. M.; Phelps, A. D. R.; Cross, A. W.; Bingham, R.; Robertson, C. W.; Whyte, Colin; He, W.; Vorgul, I.; Cairns, R. A.; Kellett, B. J.

In: Physics of Plasmas, Vol. 17, No. 5, 056501, 05.05.2010.

Research output: Contribution to journalArticle

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T1 - Numerical investigation of auroral cyclotron maser processes

AU - Speirs, David

AU - Ronald, K.

AU - McConville, S. L.

AU - Gillespie, K. M.

AU - Phelps, A. D. R.

AU - Cross, A. W.

AU - Bingham, R.

AU - Robertson, C. W.

AU - Whyte, Colin

AU - He, W.

AU - Vorgul, I.

AU - Cairns, R. A.

AU - Kellett, B. J.

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AB - When a mainly rectilinear electron beam is subject to significant magnetic compression, conservation of magnetic moment results in the formation of a horseshoe shaped velocity distribution. It has been shown that such a distribution is unstable to cyclotron emission and may be responsible for the generation of auroral kilometric radiation-an intense rf emission sourced at high altitudes in the terrestrial auroral magnetosphere. Particle-in-cell code simulations have been undertaken to investigate the dynamics of the cyclotron emission process in the absence of cavity boundaries with particular consideration of the spatial growth rate, spectral output and rf conversion efficiency. Computations reveal that a well-defined cyclotron emission process occurs albeit with a low spatial growth rate compared with waveguide bounded simulations. The rf output is near perpendicular to the electron beam with a slight backward-wave character reflected in the spectral output with a well defined peak at 2.68 GHz, just below the relativistic electron cyclotron frequency. The corresponding rf conversion efficiency of 1.1% is comparable to waveguide bounded simulations and consistent with the predictions of kinetic theory that suggest efficient, spectrally well defined emission can be obtained from an electron horseshoe distribution in the absence of radiation boundaries.

KW - aurora

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KW - plasma kinetic theory

KW - plasma simulation

KW - plasma-beam interactions

KW - terrestrial kilometric radiation

KW - plasma cavities

KW - wave modes

KW - particle emission

KW - solar wind

KW - electromagnetic radiation

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