Reflection and transmission of an electromagnetic wave by a gaseous plasma

The paper reports a study of a one-dimensional model of the interaction of an electromagnetic wave and the plasma of an ionized gas in the absence of a static magnetic field. It is shown that the reflection and transmission coefficients at the boundary of a semi-infinite plasma can be usefully discussed in terms of the Smith chart of transmission-line practice. A plasma of finite thickness is then considered, and it is found possible to avoid certain approximations that have been used in the past when plasmas with various distributions of electron density have been treated. This is achieved by carrying out the integration of the appropriate differential equations on a digital computer using quantized versions of the density and collision-frequency distributions for the electrons. This technique may be applied to plasmas with arbitrary distributions for which no analytic solutions are known. In the paper the application of the technique is restricted to certain simple distributions, namely the rectangular, triangular and half-cosine density distributions, each with a uniform distribution of collision frequency. The results for the reflection, absorption and transmission coefficients are presented graphically for a number of plasmas. Finally, the accuracy of determining the electron density from phase-bridge or interferometer measurements is discussed briefly in the light of these results.