Antenna Noise Temperature in Plasma Environment

The total noise power available at a receiving antenna on a hypervelocity space vehicle is determined by considering the engulfing plasma sheath as a uniform slab of plasma. The noise emission from the plasma is treated as a boundary-value problem which for this simple model can be completely solved. The effect of the hot vehicle surface and other external sources is included. The general conclusions are that for an isotropic plasma the main noise contributions result from the vehicle surface for RF frequencies well below the plasma frequency, from external sources for RF frequencies well above the plasma frequency, and from direct emission by the plasma for RF frequencies about the plasma frequency. The noise power from the plasma is the most significant and exhibits a pronounced peak at an RF frequency just above the plasma frequency. The effect of an anisotropic plasma sheath (due to an auxiliary magnetic field carried by the vehicle) has been investigated for magnetic field orientations normal to and parallel to the plasma. The anisotropy completely alters the spectral characteristics of the available noise power resulting in several frequency regions of weak and intense noise emission.