Modulation of ionization in the plasma column of an optical discharge

Stability of the ionization in the plasma column of an optical discharge is discussed. It is shown that a plasma filament formed by a long laser spike under optical discharge conditions may break up into a chain of bright luminous layers oriented in the direction of propagation of a laser beam and characterized by a higher gas ionization ("optical striations"). A nonlinear formulation of the problem is used to find the depth of modulation of the gas ionization.