  We compute quasinormal modes (QNMs) of the metric and gauge field
perturbations about black branes electrically and magnetically charged in the
Einstein-Maxwell-Chern-Simons theory. By the gauge/gravity correspondence, this
theory is dual to a particular class of field theories with a chiral anomaly,
in a thermal charged plasma state subjected to a constant external magnetic
field, $B$. The QNMs are dual to the poles of the two-point functions of the
energy-momentum and axial current operators, and they encode information about
the dissipation and transport of charges in the plasma. Complementary to the
gravity calculation, we work out the hydrodynamic description of the dual field
theory in the presence of a chiral anomaly, and a constant external $B$. We
find good agreement with the weak field hydrodynamics, which can extend beyond
the weak $B$ regime into intermediate regimes. Furthermore, we provide results
that can be tested against thermodynamics and hydrodynamics in the strong $B$
regime. We find QNMs exhibiting Landau level behavior, which become long-lived
at large $B$ if the anomaly coefficient exceeds a critical magnitude. Chiral
transport is analyzed beyond the hydrodynamic approximation for the five
(formerly) hydrodynamic modes, including a chiral magnetic wave.
