The Net Advance of Physics: Gamma-Ray Pulsar Emission Models, by Alice K. Harding -- Section 3C.

Inverse-Compton induced pair cascades

When , inverse Compton emission will provide the

primary spectrum to initiate the cascade, which then proceeds via

one-photon pair production and synchrotron radiation, similar to

the curvature initiated cascades. ICPC models have been

investigated by Dermer & Sturner (1994) and by Sturner et al.

(1995). The energy to which the primary electrons are accelerated

is assumed to be that only of the space-charge limited flow

potential, . However, the energies required to radiate photons with energies up to several GeV with Compton

scattering are much lower than for primary curvature radiation.

The final -ray spectra have power law indices that may be as

hard as in the case of no cascading to with a

synchrotron photon cascade contribution. Since pulsars with larger

will have softer spectra, this model may also explain the

correlation of spectral hardness with apparent age.

ICPC models cannot produce cascades several stellar radii above

the neutron star surface in pulsars whose thermal X-ray emission

from a hot polar cap dominates the non-thermal X-rays, because

the flux of soft photons decreases rapidly with altitude. In order to

reproduce the widely separated double-peaked profiles, these

models must require very small obliquities, (Sturner & Dermer 1995).

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