  The Ginzburg-Landau theory is used to model the order parameter of a
finite-size mesoscopic ring to investigate the effects of the onset of
screening currents on the transport of incoming ones. The magnetic flux breaks
the symmetry of currents between input and output stubs by means of an induced
spatial ordering upon diamagnetic and paramagnetic supercurrents circulating in
the ring. The distribution of those screening currents drives the interference
of incoming/outgoing supercurrents resulting into a sinusoidal variation of
resistance as a function of the magnetic flux even if the density of
quasiparticles is not modified by the external magnetic field.
