  We investigate the effect of external magnetic fields on equilibration in the
improved holographic QCD theory in the deconfined phase using the AdS/CFT
correspondence. In particular we calculate the quasinormal mode spectra in the
corresponding black brane solutions and study their dependence on temperature,
momentum and magnetic field, both in the scalar and the shear channels. We find
complex patterns in the motion of quasinormal modes on the complex plane,
including certain cross overs between the lowest lying modes under varying
magnetic field, momentum and temperature. We also discover a critical value of
the magnetic field $B_c$ above which the hydrodynamic approximation breaks
down, as the imaginary part of the first excited quasi-normal mode in the shear
channel becomes smaller than that of the hydro mode.
