Influence of a collisional plasma background on the classification of the two-stream instability

This paper gives a general method for finding the line of marginal absolute instability and lines of equal asymptotic growth rates in parameter space for streams and a collisional plasma when the stability analysis for the same problem without plasma is known. The region of absolute instability is seen to be diminished whenever ν ≠ 0 (collision frequency ≠ 0). For ν = 0 the plasma background does not change the region of absolute instability, but growth rates are diminished. For this case and two cold streams the asymptotic growth rates are found analytically. Previous results are seen to be too narrow and singular to give an adequate picture of what is happening.