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 1079-7114 (

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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.