Electron distribution functions in laser fields

A short review of the properties of electron distribution functions in a fu lly ionized plasma in the presence of high-frequency laser radiation is giv en. Weak and strong field situations are considered. In a weak held, when t he amplitude of the electron quiver velocity in the field is smaller than t he electron thermal velocity the distributions of both the thermal and the under thermal electrons are considered. The conditions are shown when it is necessary to take into account the deviation of the electron distribution function from a Maxwellian. In a strong field the kinetics of the electron is strongly determined by the field intensity and the distribution function in the coordinate system oscillating with the radiation frequency is aniso tropic under broad physical conditions, and may be approximated by a bi-Max wellian distribution with two different transverse and longitudinal tempera tures. Among the most peculiar features of the laser modified electron dist ribution functions, it is worth quoting the pathway of the anisotropy evolu tion. Depending on the laser field parameters, the distribution function in the initial stages of the laser-plasma interaction is either elongated or squeezed parallel to the field polarization. In the later stages it evolves towards isotropization, which is always approached from the elongated shap e. Thus, an initially squeezed distribution function first evolves towards an elongated shape and subsequently towards isotropization. The physical or igin and the consequences of the reported features are discussed. In additi on, a number of physical processes for which the theory demands the use of the described non-equilibrium distribution functions are briefly addressed.