On anomalous Doppler instability in auroral and laboratory plasmas

This paper examines different conditions of appearance of anomalous Doppler instability when an electron beam moves under the presence of a strong magnetic field. The situations considered here are relevant to wave-particle interactions in space plasmas like lower-hybrid waves generated by Cherenkov and anomalous Doppler resonances [1] as well as to the experiment set at the University of Strathclyde, UK, to examine magnetized electron beams instabilities [2]. We consider growth rates produced by the relevant distribution functions with the beam drift velocity exceeding the wave velocity. Possible experiment configurations are addressed including a dielectric filled waveguide as well as a wave-slowing dielectric with a vacuum core at the axis for the electron beam. Possibilities to distinguish the anomalous Doppler resonance from other accompanying beam instabilities [3] are discussed. \\[4pt] [1] R. Bingham et al, J. Plasma Physics, 76, pp. 539-546 (2010) \\[0pt] [2] D. C. Speirs et al, Phys. Plasmas, 17, 056501 (2010) \\[0pt] [3] I. Vorgul et al, Phys. Plasmas, 18, 056501 (2011).