Landau damping of plasma waves

The Landau theory of collisionless damping of plasma waves is discussed. The arguments are given in favor that one of the two contours used by Landau in his theory should be understood in this problem as the base Landau contour, however, it is not the contour typically referred to as the “Landau contour.” The place that this Landau contour should occupy is found in the approximate analytic theory of weak damping of waves, as well as in the quasi-stationary theory of ion-acoustic turbulence.