Abstract
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.
Highlights
Ionospheric radio heating experiments performed over the past decades have utilised the ionosphere as a ‘natural plasma laboratory’ to study the interaction of electromagnetic waves with plasma in parameter regimes not accessible in laboratory experiments [1,2,3,4,5]
Large-scale two-dimensional electromagnetic simulations of ionospheric heating scenarios have been performed in other works [6, 16, 17] but not with the aim of simultaneously resolving electrostatic Langmuir turbulence excited by the electromagnetic driver
Note that the input power flux represents an equivalent radiated power (ERP) of only 35 MW assuming that the distance between the transmitter and F2 peak is around 250 km, which is considerably less than the maximum ERP of HAARP which is several GW
Summary
Ionospheric radio heating experiments performed over the past decades have utilised the ionosphere as a ‘natural plasma laboratory’ to study the interaction of electromagnetic waves with plasma in parameter regimes not accessible in laboratory experiments [1,2,3,4,5]. Large-scale two-dimensional electromagnetic simulations of ionospheric heating scenarios have been performed in other works [6, 16, 17] but not with the aim of simultaneously resolving electrostatic Langmuir turbulence excited by the electromagnetic driver. The simulation does allow the modelling of driver depletion of the electromagnetic wave which may be important at large input powers and conditions of highly developed turbulent modulation of the plasma. The model equations and their spatial discretisation are presented; appendix A describes the timestepping scheme
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