A new Weibel source due to the inverse bremsstrahlung absorption is presented. It has been shown that in homogeneous plasmas, this mechanism may drive strong collisionless Weibel modes with growth rates of order of ␥ϳ10 11 s Ϫ1 and negligible group velocities. In the laser-produced plasmas, for short laser wavelengths ( L Ͻ1 m) and high laser fluxes (IϾ10 14 W/cm 2 ), this Weibel source is most efficient as the ones due to the heat flux and the plasma expansion. The useful scaling law of the convective e-foldings, with respect to the laser and the plasma parameters, is also derived. ͓S1063-651X͑97͒07206-1͔PACS number͑s͒: 52.40.Nk, 52.35.Qz

Using the projection operators, the analytic solution of the Vlasov equation linearized with respect to the global Maxwellian distribution function is presented. The expressions of the generalized quasistatic collisionless transport coefficients are computed, and in particular, a strong plasma temperature anisotropy and a convective heat flux are pointed out. The results obtained have been used to close the fluid equations. The spectral range validity of the collisionless fluid equations is also studied with the use of the plasma response function.