Anisotropic electron-distribution function in inverse-bremsstrahlung-heated plasmas

The electron-distribution function in homogeneous plasmas heated by a high-frequency laser field is calculated in velocity space from the Vlasov-Landau equation. The kinetic model is valid for moderate laser intensity defined by the relevant parameter alpha = v(0)(2)/v(t)(2) < 0.5 where v(0) and v(t) are the peak velocity of oscillation in the high-frequency electric field and the thermal velocity, respectively. The results obtained constitute an improvement of the results reported in the literature devoted to weak electric field intensities. The electron-distribution function is calculated solving the kinetic equation with the use of the Legendre polynomial expansion within the laser field dipole approximation. It results in an infinite set of equations for the isotropic component f(0)(v) and the anisotropic components f(n)>= 1(v) that we have solved numerically with appropriate truncation. For the second anisotropy f(2)(v), we found that its maximum increases from the weak electric field intensity (alpha < 0.01) to a moderate one (alpha = 0.5) by a factor f(2max)(alpha = 0.5)/f(2max)(alpha = 0.01) approximate to 48. Applications to the radiation pressure, electromagnetic instabilities, and photoabsorption are also considered.