Geometric aspects of HF driven Langmuir turbulence in the ionosphere

Abstract. The geometric aspects of HF-generated Langmuir turbulence in the ionosphere and its detection by radars are theoretically discussed in a broad approach, including local modelling (damped and driven Zakharov system), basic parametric instabilities, polarization and strength of the driving electric field, and radar configurations. Selected examples of numerical results from the local model are presented and discussed in relation to recent experiments, with emphasis on recent experiments at the EISCAT facilities. Anisotropic aspects of the cavitation process in the magnetized plasma are exhibited. Basic processes of cascades and cavitation are by now well identified in these experiments, but a few problems of the detailed agreement between theory and experiments are pointed out.