Abstract
SEVERAL investigations1 published within the past few years deal with the interaction of a stationary plasma in the outer regions of the ionosphere (exosphere) with an assembly of charged particles trapped in the Earth's magnetic field. Such an interaction results in electromagnetic radiation within the audible range which is detected at the Earth's surface in the form of continuous white noise or whistlers. The trapped particles spiral around the lines of the magnetic field B0 and form a ‘helical beam’, characterized by velocity components β⊥c and β∥C which are, respectively, perpendicular and parallel to B0 (c is the velocity of light). A whistler wave thus produced and aligned in the direction of B0 is usually described by the equalities: in which ω is the frequency, k is the wave number, β2 = β∥2 + β⊥2, Ωe is the electron gyrofrequency, and n = ωe2/ω(ω − Ωe) is the refractive index for the whistler mode (ωe is the plasma frequency).
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NEUFELD, J., WRIGHT, H. Generation of Whistler Waves by Helical Electron Beams. Nature 203, 288–289 (1964). https://doi.org/10.1038/203288a0
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DOI: https://doi.org/10.1038/203288a0
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