Propagation of EM Signals through a High Speed Flow with Ion Acoustic Wave Instabilities when Signal Frequencies are close to Plasma Frequency of the Flow

It is known that in the absence of external magnetic field a high speed flow with velocity shear will lead to ion acoustic wave instabilities. Electromagnetic (EM) signals propagating through the flow will get scattered by the instabilities resulting in shifts in signal wavenumbers and frequencies. When the EM signal frequencies are large compared to the plasma frequency of the flow the scattering process is entirely electromagnetic in nature. However, when the signal frequencies are close to the plasma frequency of the flow, the scattered fields will be partly electrostatic (Langmuir) and partly EM. Multiple scattering will lead to coupling and energy exchange between the electrostatic and EM parts. The coherent part of the scattered waves has the same spectrum as that of the source signal. The diffuse part is obtained as a convolution (in wavenumber and frequency) of the source signal with the spectrum of electron density fluctuations. This is a constrained convolution in the sense that the spectrum has to satisfy the IAW dispersion relation. The mean free path is a key quantity that determines the significance of coherent and diffuse parts. We will highlight details of the impact of the IAW turbulence on radiation and reception of EM signals with the help of examples.