ABSTRACT
For normal laser light incidence on plasma the ponderomotive force fp per unit volume is given by (the proof of this equation is given at the end of section 4.1 and in section 4.2)
fp ¼ !2p
8!2L rhE2i ð4:1Þ
where !2p ¼ 4nee2=me is the plasma frequency, !L is the angular laser frequency, Es is the space-dependent electric field of E, given by
E ¼ EsðrÞ cos!Lt ð4:2Þ and the time average over one laser oscillating period (i.e. over one wavelength) is denoted by h i. The ponderomotive force is a nonlinear force where a high-frequency electromagnetic laser field induces a slow time scale force. This force is involved in many physical phenomena, such as:
(a) momentum transfer to the target (Hora 1969,Arad et al. 1980,Hora 1981); (b) self-focusing and filamentation of the laser beam (Kaw et al. 1973, Max
1976); (c) plasma profiles density changes such as the formation of cavitons and
solitons (Morales and Lee 1977, Mulser and van Kessel 1977, Evely and Morales 1978);
(d) parametric instabilities (Chen 1977); (e) second harmonic generation (Jackel et al. 1981); (f ) magnetic field generation (Stamper and Tidman 1973, Lehner 1994,
Horovitz et al. 1997, Horovitz et al. 1998).
