  We analyse the Hanle effect on a closed $F_g\to F_e=F_g+1$ transition. Two
configurations are examined, for linear- and circular-polarized laser
radiation, with the applied magnetic field collinear to the laser light
wavevector. We describe the peculiarities of the Hanle signal for
linearly-polarized laser excitation, characterized by narrow bright resonances
at low laser intensities. The mechanism behind this effect is identified, and
numerical solutions for the optical Bloch equations are presented for different
transitions.
