Large-scale numerical simulation of ionospheric Langmuir turbulence excited by a radio frequency electromagnetic wave

A numerical simulation is presented concerning an L/O mode electromagnetic wave propagating normally into an overdense magnetised plasma with a smooth density gradient leading to excitation of Langmuir turbulence in the vicinity of the reflection point. The simulation parameters are chosen to represent an ionospheric radio frequency heating experiment but may have relevance to other situations. The simulation model is one-dimensional for large-scale electromagnetic waves and two-dimensional for short-scale electrostatic waves. This allows consideration of local modulational and parametric-decay instabilities as well as the larger scale depletion of the driver electromagnetic wave by anomalous absorption due to the excited turbulence. Simulated growth rates are shown to be in broad agreement with expected values and the evolution of the spatial distribution of the turbulence and driver field profile are presented along with simulated scatter radar spectra.