Open AccessCyclotron amplification of whistler‐mode waves: A parametric study relevant to discrete VLF emissions in the Earth's magnetosphere
Author(s) -
Pasmanik D. L.,
Demekhov A. G.,
Nunn D.,
Trakhtengerts V. Y.,
Rycroft M. J.
Publication year - 2002
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2001ja000256
Subject(s) - magnetosphere , whistler , physics , geophysics , computational physics , cyclotron , van allen radiation belt , instability , magnetic field , space physics , noise (video) , electron , mechanics , nuclear physics , quantum mechanics , artificial intelligence , computer science , image (mathematics)
We study the amplification of ducted whistler‐mode waves in the Earth's magnetosphere by the cyclotron instability for different types of energetic electron distributions in velocity space. Particular attention is paid to the comparison between cases of smooth distribution functions and those with sharp gradients (“steps”) in velocity space, which arise naturally owing to interactions with noise‐like VLF emissions. We show that step‐like features greatly favor the amplification of whistler‐mode waves propagating along the Earth's magnetic field line and hence the generation of narrowband VLF emissions even if the electron anisotropy is only moderate. The results obtained are discussed in light of observations of discrete VLF emissions from the magnetosphere, in particular those of Bell et al. [2000].