  This work looks at some definitive signatures of magnetars, in particular of
period closures accompanied by a decline of X-ray radiation in two models. We
review some of the previous works which are based on the well known dynamo
model in which the star is born with a period of a few milliseconds at high
temperatures. In such a convection regime the dynamo mechanism can amplify the
the magnetic fields to the magnetar value. This is in contrast to a screened
core model which posits that a high density phase transition occurs in the
inner core of magnetars that dynamically aligns all the neutron magnetic
moments producing a large magnetic field in the core. The accompanying change
of flux gives rise to shielding or screening currents in the surrounding high
conductivity plasma that do not permit the field to exit to the surface.
Ambipolar diffusion then transports the field to the crust dissipating energy
in neutrinos and X-rays. The up-welling field cleaves the crust resulting in
flares and X-ray radiation from ohmic dissipation in the crust till the
screening currents are spent and the surface polar field attains its final
value. In the dynamo model the polar magnetic field decreases with time whereas
in our screened model it increases to its final value. One consequence of this
is that in the latter model, as a function of time and period, the ratio of the
dipole radiation loss, $\dot E$ to the X-ray luminosity, $ L_X$, is a 'U'
curve, indicating that it is the exponential decline in $L_X$, that brings
closure to the periods that are observed for magnetars.
