Packets of cyclotron waves induced by electron beam injection from the Space Shuttle. I - Linear theory. II - Nonlinear theory

This paper investigates the generation mechanism responsible for the packets of electron cyclotron waves induced by an electron beam injected from the Space Shuttle and measured by Spacelab I instruments. The observed electron cyclotron emissions as well as their amplitude modulation are explained using a linear and a nonlinear treatments. Using a linear theory, it is shown that the emissions consist of the electronic Bernstein modes which are generated by an interaction between the neutralization return current and the ambient ionospheric plasma, and not directly by the primary beam. The observation of successive harmonic packets around the fundamental wave is interpreted using a two-dimensional single-wave model of the nonlinear interaction between a finite size ring beam and an infinite homogeneous magnetized plasma. 43 refs