  In a conducting medium held at finite temperature, free carriers are
performing Brownian motion and generate fluctuating electromagnetic fields. We
compute the averaged Lorentz force density that turns out nonzero in a thin
sub-surface layer, pointing towards the surface, while vanishing in the bulk.
This is an elementary example of rectified fluctuations, similar to the Casimir
force or radiative heat transport. Our results also provide an experimental way
to distinguish between the Drude and so-called plasma models.
