  The non-linear back reaction of accelerated cosmic rays at the shock fronts,
leads to the formation of a smooth precursor with a length scale corresponding
to the diffusive scale of the energetic particles. Past works claimed that
shocklets could be created in the precursor region of a specific shock width,
which might energize few thermal particles to sufficient acceleration and
furthermore this precursor region may act as confining large angle scatterer
for very high energy cosmic rays. On the other hand, it has been shown that the
smoothing of the shock front could lower the acceleration efficiency. These
controversies motivated us to investigate numerically by Monte Carlo
simulations the particle acceleration efficiency in oblique modified shocks.
The results show flatter spectra compared to the spectra of the pressumed sharp
discontinuity shock fronts. The findings are in accordance with theoretical
predictions, since the scattering inside the precursor confines high energy
particles to further scattering, resulting in higher energies making the whole
acceleration process more efficient.
