  The Chiral Magnetic Effect (CME) -- the separation of positive and negative
electric charges along the direction of the external magnetic field in
quark-gluon plasma and other topologically non-trivial media -- is a
consequence of the coupling of electrodynamics to the topological gluon field
fluctuations that form metastable $CP$-odd domains. In phenomenological models
it is usually assumed that the domains are uniform and the influence of the
domain walls on the electric current flow is not essential. This paper
challenges the latter assumption. A simple model consisting of a uniform
spherical domain in a uniform time-dependent magnetic field is introduced and
analytically solved. It is shown that (i) no electric current flows into or out
of the domain, (ii) the charge separation current, viz. the total electric
current flowing inside the domain in the external field direction, is a
dissipative Ohm current, (iii) the CME effect can be produced either by the
anomalous current or by the boundary conditions on the domain wall and (iv) the
charge separation current oscillates in plasma long after the external field
decays. These properties are qualitatively different from the CME in an
infinite medium.
