Abstract
The development of a longitudinal—transverse instability in a plasma with the anisotropic velocity distribution of electrons produced by the tunnelling ionisation of a target by a short laser pulse is studied. The dependences of the growth rate of this longitudinal—transverse instability on the wave number and the propagation angle of perturbations are investigated. It is shown that the increasing longitudinal electrostatic field in a rather broad angular region is comparable with the exciting magnetic field. It is pointed out that the longitudinal—transverse instability of the anisotropic plasma can lead to the additional absorption of laser radiation by the nonthermal fluctuations of the electron density.