  The problem of reconstruction of a flow of conducting incompressible fluid
generating a given magnetic mode is considered. We use the magnetic induction
equation to derive ordinary differential equations along the magnetic field
lines, which give an opportunity to determine the generating flow, if
additional data is provided on a two-dimensional manifold transversal to
magnetic field lines, and show that an arbitrary solenoidal vector field can
not be a neutral magnetic mode sustained by any flow of conducting fluid.
