Echo phenomena in plasma and plasmalike media

The phenomenon of echo is examined with emphasis on the theory of nonlinear echo effects in plasma and plasma-like media and on methods used for the quantitative description of echo. The applicability limits of the self-consistent and ballistic approaches to echo description are analyzed. New methods are presented for wave transformation in plasma and for the dispersal of supercritical plasma layers and nontransparency regions using the echo effect. Some diagnostic uses of the echo, including the diagnostics of collisions and microturbulence in plasma, are discussed.