Radiation from nonuniform charged particle beams in ionospheric plasmas

The radiation from a class of nonuniform charged particle beams of finite dimensions moving through a magnetoplasma is studied. The beam structures include bunched beams which could result from natural interaction of plasma‐supported waves with the beam particles or those which could be generated by spacecraft‐borne particle accelerators. The generation of narrow band noise by beam structures generated by whistler wave‐beam particle interaction is illustrated. It is also shown how radiation by bunched particles remains finite in regions of refractive index resonances regardless of how slowly the particles move in contrast to the theoretical result for radiation from individual particles which unrealistically gives infinite radiated power. The theory developed includes thermal effects, including temperature anisotropy for the electrons and ions. Illustrative numerical results for the special case of a single electron with zero perpendicular velocity and a large axial velocity are given using two warm plasma theories. It is shown that near the upper hybrid resonance frequency, radiation into thermal and cold plasma modes is comparable.