(Abridged) Gamma-ray emission from pulsars has long been modeled using avacuum dipole field. This approximation ignores changes in the field structurecaused by the magnetospheric plasma and strong plasma currents. We present thefirst results of gamma-ray pulsar light curve modeling using the more realisticfield taken from 3D force-free magnetospheric simulations. Having the geometryof the field, we apply several prescriptions for the location of the emissionzone, comparing the light curves to observations. We find that the conventionaltwo-pole caustic model fails to produce double-peak pulse profiles, mainlybecause the size of the polar cap in force-free magnetosphere is larger thanthe vacuum field polar cap. The conventional outer-gap model is capable ofproducing only one peak under general conditions, because a large fraction ofopen field lines does not cross the null charge surface. We propose a novel"separatrix layer" model, where the high-energy emission originates from a thinlayer on the open field lines just inside of the separatrix that bounds theopen flux tube. The emission from this layer generates two strong caustics onthe sky map due to the effect we term "Sky Map Stagnation" (SMS). It is relatedto the fact that force-free field asymptotically approaches the field of arotating split monopole, and the photons emitted on such field lines in theouter magnetosphere arrive to the observer in phase. The double-peak lightcurve is a natural consequence of SMS. We show that most features of thecurrently available gamma-ray pulsar light curves can be reasonably wellreproduced and explained with the sepatratrix model using the force-free field.Association of the emission region with the current sheet will guide moredetailed future studies of the magnetospheric acceleration physics.
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