Backward wave cyclotron-maser emission in the auroral magnetosphere

Speirs, D. C. and Bingham, R. and Cairns, R. A. and Vorgul, I. and Kellett, B. J. and Phelps, A. D R and Ronald, K. (2014) Backward wave cyclotron-maser emission in the auroral magnetosphere. Physical Review Letters, 113 (15). 155002. ISSN 0031-9007

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    In this Letter, we present theory and particle-in-cell simulations describing cyclotron radio emission from Earth's auroral region and similar phenomena in other astrophysical environments. In particular, we find that the radiation, generated by a down-going electron horseshoe distribution is due to a backward-wave cyclotron-maser emission process. The backward wave nature of the radiation contributes to upward refraction of the radiation that is also enhanced by a density inhomogeneity. We also show that the radiation is preferentially amplified along the auroral oval rather than transversely. The results are in agreement with recent Cluster observations.