  We study the small mass limit of the equation describing planar motion of a
charged particle of a small mass $\mu$ in a force field, containing a magnetic
component, perturbed by a stochastic term. We regularize the problem by adding
a small friction of intensity $\e>0$. We show that for all small but fixed
frictions the small mass limit of $q_{\mu, \e}$ gives the solution $q_\e$ to a
stochastic first order equation, containing a noise-induced drift term. Then,
by using a generalization of the classical averaging theorem for Hamiltonian
systems by Freidlin and Wentzell, we take the limit of the slow component of
the motion $q_\e$ and we prove that it converges weakly to a Markov process on
the graph obtained by identifying all points in the same connected components
of the level sets of the magnetic field intensity function.
