  In a three-dimensional Riemannian manifold M that admits a unit Killing
vector field $\xi$, we regard $\xi$ as a magnetic vector field. A magnetic Hopf
surface is a surface obtained by Lie dragging the magnetic curve with $\xi$.
Then we characterize Sasakian structure on M from magnetic Hopf surfaces. That
is, we show that if an arbitrary magnetic Hopf surface is a constant mean
curvature surface then M is a Sasakian manifold.
