  Recently, it is found that when an external magnetic field parallel to the
boundary is applied, Weyl anomaly gives rises to a new anomalous current
transport in the vicinity of the boundary. At the leading order of closeness
from the boundary, the current is determined universally by the central charge
of the theory. In this paper, we give a holographic proof for the existence and
universality for this transport phenomena. We show that the current is
independent of boundary conditions in four dimensions while it depends on
boundary conditions in other dimensions. We also study the backreaction of the
bulk Maxwell fields on the AdS spacetime and obtain the holographic Weyl
anomaly for 5d BCFTs in presence of the background field strength.
