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This thesis presents a theoretical study of the interaction of intense, ultrashort laser pulses with overdense
plasmas. Main objectives are to understand the basic phenomenon which leads to the formation
of non-linear electrostatic coherent wave structures in form of either solitary ion acoustic waves (SAW)
or collisionless shock waves (CSW). These different types of waves have been classified according to
Sagdeev’s theory and related formulas have been used for comparison with the numerical results. The
particular focus is on the effect on ion acceleration, by means of ion refection by the moving electrostatic
field associated to the shocks/solitons. An extensive numerical study by 1D PIC simulations has
been performed and in particular the differences arising between linearly polarized pulses and circularly
polarized pulses have been discussed. In a cold plasma, ion bunches produced by “hole boring” (HB)
radiation pressure acceleration at the target surface may propagate in the bulk as solitary waves. The acceleration
mechanism of these ion bunches has been discussed pointing out a distinction between shock
acceleration (SA) and HB acceleration, also with respect to some recent experimental results. Stability
of (SAW) or (CSW) and ion reflection from them has been found to be strongly dependent on the initial
velocity distribution of ions. The effect of both the ion and the electron temperature on the generation
and evolution of solitary acoustic waves have been discussed.