The general properties of the non-thermal non-pulsed X-ray emission of rotation powered pulsars are investigated in the context of a pulsar wind nebula model .
An examination of the observed X-ray emission from a sample of 23 pulsars in the energy range between 2-10 keV reveals that the relation of X-ray luminosity , L _ { x } , to the pulsar spin down power , \dot { E } , is steeper for the non-pulsed component than for the pulsed component .
Specifically , L _ { x } ^ { npul } \propto \dot { E } ^ { 1.4 \pm 0.1 } for the non-pulsed component , whereas L _ { x } ^ { pul } \propto \dot { E } ^ { 1.2 \pm 0.08 } for the pulsed component .
The former relation is consistent with emission from a pulsar wind nebula model in which L _ { x } ^ { npul } \propto \dot { E } ^ { p / 2 } where p is the power law index of the electron energy distribution .
The relation for the pulsed component , on the other hand , is consistent with a magnetospheric emission model .
In addition , the photon spectral index , \Gamma , was found to be correlated to the conversion efficiency of spin down power to non-pulsed X-ray emission with greater efficiencies for \Gamma \sim 2 - 2.5 than for \Gamma \sim 1.5 - 2 .
Such a relation is naturally understood within the framework of a pulsar wind nebula model with the former relation corresponding to the emission of X-rays in the fast cooling regime and the latter relation corresponding to emission in the slow cooling regime .

The X-ray properties of pulsar wind nebulae are sensitive to the physical conditions ( e.g. , the density and magnetic field ) of the interstellar medium and can lead to important differences between the X-ray emission characteristics ( luminosity , photon spectral index and emission morphology ) of pulsars in various environments .
Such wind nebulae can contribute to the non-thermal symmetric emission morphology ( point-like ) and elongated emission morphology ( tail-like ) from sources similar to Geminga and PSR B1757-24 .