  We explore the hardness-intensity correlations observed in several AXPs and
SGRs within the framework of a thermally emitting magnetar model. Using our
detailed atmosphere models and taking into account reprocessing of the surface
emission by the magnetosphere, we show that the hardness of the surface spectra
increases with increasing temperature and hence the changes in the effective
temperatures of the outer layers of the star alone can account for the observed
correlations. We conclude that the slow release of the heat deposited in the
deep crust during a magnetar burst naturally accounts for the spectral changes
during the afterglow. The correlations are further enhanced by changes in the
structures of the magnetic currents during or following a burst. However, the
additional hardening produced by scattering of the surface photons off the
magnetospheric charges saturates at moderate values of the scattering optical
depth.
