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Numerical investigation of auroral cyclotron maser processes

Speirs, David and Ronald, K. and McConville, S. L. and Gillespie, K. M. and Phelps, A. D. R. and Cross, A. W. and Bingham, R. and Robertson, C. W. and Whyte, Colin and He, W. and Vorgul, I. and Cairns, R. A. and Kellett, B. J. (2010) Numerical investigation of auroral cyclotron maser processes. Physics of Plasmas, 17 (5). 056501. ISSN 1070-664X

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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.

Item type: Article
ID code: 28938
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, Plasma physics. Ionized gases, Condensed Matter Physics
Subjects: Science > Physics > Plasma physics. Ionized gases
Department: Faculty of Science > Physics
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Depositing user: Pure Administrator
Date Deposited: 25 Mar 2011 15:31
Last modified: 27 Mar 2014 09:12
URI: http://strathprints.strath.ac.uk/id/eprint/28938

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