Numerical simulation of unconstrained cyclotron resonant maser emission
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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 (AKR) an intense rf emission sourced at high altitudes in the terrestrial auroral magnetosphere. PiC 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 to 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 2.68GHz, 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 radiation emission can be obtained from an electron horseshoe distribution in the absence of radiation boundaries.
Speirs , D C , Gillespie , K M , Ronald , K , McConville , S L , Phelps , A D R , Cross , A W , Bingham , R , Kellett , B J , Cairns , R A & Vorgul , I 2014 , Numerical simulation of unconstrained cyclotron resonant maser emission . in 15th International Congress on Plasma Physics (ICPP2010) & 13th Latin American Workshop on Plasma Physics (LAWPP2010) . Journal of Physics Conference Series , vol. 511 , IOP Publishing Ltd. , Bristol , 15th International Congress on Plasma Physics (ICPP) / 13th Latin American Workshop on Plasma Physics (LAWPP) , Chile , 8/08/10 . DOI: 10.1088/1742-6596/511/1/012052conference
15th International Congress on Plasma Physics (ICPP2010) & 13th Latin American Workshop on Plasma Physics (LAWPP2010)
© 2014 The Authors. Published under licence by IOP Publishing Ltd. The following article appeared in D C Speirs et al 2014 J. Phys.: Conf. Ser. 511 012052 and may be found at http://iopscience.iop.org/1742-6596/511/1/012052/. Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
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