  We report on critical currents and voltage noise measurements in Niobium
strips in the superconducting state, in the presence of a bulk vortex lattice
($B < B_{C2}$) and in the surface superconducting state ($B_{c2}< B < B_{C3}$).
For homogeneous surfaces, the correlation length of the current fluctuations
can be associated with the electromagnetic skin depth of vortex superficial
instabilities. The modification of the surface state by means of low energy
irradiation induces a strong modification of the critical current and of the
noise. The appearance of a corner frequency in the spectral domain can be
linked with the low wave-vectors of the artificial corrugation. Since this
latter occurs only for $B < B_{C2}$, we propose that the long-range
interactions allow the correlation length to extend up to values imposed by the
surface topography.
