Effects of density profile steepening on generation of suprathermal particles, harmonics and magnetic fields in a laser produced plasma

The propagation of obliquely incident p-polarized laser radiation through a laser plasma with a density profile steepening in the domain of the critical point is considered. Such a density profile seems to be a long term profile in a laser produced plasma. It is shown that the structure of the laser radiation electric field is significantly changed in reference to Ginzburg's treatment. In the case of total absorption of the laser radiation a simple expression for the electric field is obtained. The effects of such a new structure of the electric field on the generation of suprathermal particles, harmonics and magnetic fields is considered. It is shown that in this field, ions (due to the ponderomotive force) could be accelerated up to the energies of the order of 10 keV. It is also shown that such a structure of the electric field significantly affects generation of magnetic fields (by the p-component of the laser radiation electric field) in plasma. Finally, it is shown that due to the density profile steepening a direct transformation (as a consequence of parametric instability) of laser radiation into ω0.2-1 harmonic takes place. (author)