Filamentation instability of relativistic-intensity electromagnetic waves in a plasma

A study is reported of a filamentation instability of electromagnetic waves making allowance for the relativistic effect and for the electron striction. The increment and the threshold intensity are found for a semibounded homogeneous plasma. The relativistic effect and the electron striction favor the development of an instability. Numerical calculations are used also to study the case of an inhomogeneous plasma with a linear profile.