  The fraction of heavy vector mesons detected after a heavy ion collision
provides information about the possible formation of a plasma state. An
interesting framework for estimating the degree of dissociation of heavy mesons
in a plasma is the holographic approach. It has been recently shown that a
consistent picture for the thermal behavior of charmonium and bottomonium
states in a thermal medium emerges from holographic bottom up models. A crucial
ingredient in this new approach is the appropriate description of decay
constants, since they are related to the heights of the quasiparticle peaks of
the finite temperature spectral function. Here we extend this new holographic
model in order to study the effect of magnetic fields on the thermal spectrum
of heavy mesons. The motivation is that very large magnetic fields are present
in non central heavy ion collisions and this could imply a change in the
dissociation scenario. The thermal spectra of $ c \bar c$ and $ b \bar b \, $ S
wave states is obtained for different temperatures and different values of the
magnetic $e B$ field.
