  We have studied the longitudinal and the transverse velocity fluctuations of
a moving vortex lattice (VL) driven by a transport current. They exhibit both
the same broad spectrum and the same order of magnitude. These two components
are insensitive to the velocity and to a small bulk perturbation. This means
that no bulk averaging over the disorder and no VL crystallization are
observed. This is consistently explained referring to a previously proposed
noisy flow of surface current whose elementary fluctuator is measured
isotropic.
