The radiation from a density-modulated beam of ions, which penetrates a plasma perpendicular to a strong magnetic field B0, is investigated in two simplified situations: (a) the beam is an infinite plane parallel to B0, and (b) the beam is an infinite cylindrical surface parallel to B0, the radius of the cylinder being the gyroradius of the beam particles. This latter beam can be ideally constructed by injecting into a plasma a linear beam, modulated at a frequency which is an integral multiple of the gyrofrequency of the beam particles and incident in a direction which forms a very small angle with a plane perpendicular to B0.In both situations some resonances of the Poynting vector are found. The resonance, which occurs when the modulation frequency is equal to the "ion-resonance" frequency, is specifically investigated, taking into account the finite electric conductivity of the plasma. It is shown that, under appropriate conditions, the beam-plasma interaction at this resonance becomes very strong.
Generation of high-power electromagnetic radiation by a beam-driven plasma antenna