  We study the spacetime evolution of electric $(\textbf{E})$ and magnetic
$(\textbf{B})$ fields along with the electromagnetic anomaly
$(\textbf{E}\cdot\textbf{B})$ in the presence of electric ($\sigma$) and chiral
magnetic ($\sigma_{\chi}$) conductivities in Au+Au collisions at
$\sqrt{s_{\mathrm{NN}}}=200$~GeV. By comparing to the Lienard-Wiechert
solutions with zero conductivities, we observe a symmetry breaking of the
electromagnetic field in a conducting medium with respect to the reaction
plane. The decay of the field is also significantly decelerated after the
conductivities are introduced. Similar effects are also found for the dipole
structure of $\textbf{E}\cdot\textbf{B}$ as well as the quadrupole structure of
$(\textbf{E}\cdot\textbf{B})\textbf{B}$, which may finally affect the charge
separation of the elliptic flow coefficient of hadrons observed in high-energy
nuclear collisions.
