The impact of fluctuations on the propagation of radio frequency waves

In fusion devices, radio frequency (RF) electromagnetic waves encounter turbulent plasmas in the edge region as they propagate from the excitation structures to the core of the device. In order to optimize heating and current drive by RF waves, it is necessary to understand the effect of turbulence on the propagation characteristics of the waves. A common approach towards quantifying the effects of turbulence on RF waves is the Kirchhoff technique. The wave fields and their normal derivatives are evaluated at a surface, separating two different densities, using physical optics. The fields at any point on this surface are approximated to be the same as the fields on a tangent plane at that point. The results from this theoretical analysis are compared with full-wave numerical simulations. A complementary set of studies is to construct the effective permittivity of turbulent plasmas that are a mix of coherent (blobs and filaments) and incoherent fluctuations. Towards this end, we use the effective medium approximation and the homogenization theory for magnetized plasmas to formulate the plasma permittivity. This effective permittivity will be implemented in the full-wave and in the physical optics studies of RF scattering.