On the Theory of Beam-Plasma Instability in the Nonstationary Plasma

The beam instability in the plasma with density slowly varying with time has been investigated using the potential approximation. It has been shown that a frequency shift occurs in the amplified signal propagating in such an electrodynamic system; analytical relations for determining the value of this shift have been obtained. It is demonstrated that the frequency is shifted most strongly as the plasma density decreases, when the Langmuir frequency of plasma electrons approaches the signal frequency and the instability increment increases with time.