Abstract
A high power millimetre wave, employed for communication with a re-entry space vehicle surrounded by a high-density plasma sheath, is affected by linear and nonlinear effects. A signal originating from the ground suffers diffraction divergence through space, prior to entering the fast evolving plasma sheath surrounding the vehicle, and undergoes time dependent absorption inside the sheath. The net signal loss due to diffraction and absorption varies as the spacecraft approaches the ground. The wave launched from the spacecraft for downward communication has a large amplitude in the plasma sheath and gives rise to nonlinear effects. The millimetre wave heats the electrons more strongly in the region where the wave intensity is maximum, causing ambipolar diffusion of the plasma leading to an increase in the refractive index at the axis, thus self-focusing the millimetre wave signal. In free space, after passing through the plasma sheath, the beam suffers defocusing.
Published Version
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