Simultaneous emissions at harmonics and half harmonics of the electron gyrofrequency

Experiments done in space and laboratory on the interaction of an electron beam and a magnetized plasma exhibit the simultaneous excitation of waves near harmonics and half harmonics of the electron gyrofrequency ωc. No theoretical explanation was available up to now for these double ECH series. The dispersion equation for electrostatic modes has been solved for an anisotropic maxwellian plasma with a suprathermal population (''beam'' in the text), such a distribution presenting both anisotropy and regions of ∂f0/∂v>0. Double series of ECH can indeed be reproduced numerically by this way, for a propagation oblique to the magnetic field. (author) 4 refs., 3 figs