Until now the Compton Gamma-Ray Observatory has detected pulsed gamma-ray emission from about 10 isolated pulsars, and more than a dozen X-ray pulsars have been detected by other satellites. Simulations of these emission processes in neutron star magnetospheres have not been able to pin down the location of the acceleration and emission regions whether the acceleration of particles occurs near the neutron star surface (polar cap models) or many stellar radii from the surface near the light cylinder (outer gap models). The team will improve current simulations by introducing realistic luminosities and geometries of radio and gamma-ray beams for both the polar cap and outer gap models. These calculations will put the polar cap and outer gap models on the same footing within the same calculation normalized by the comparison of the simulated radio pulsars with those observed by a selected group of radio surveys. The team will investigate further discriminating signatures by studying the correlations between the radio profiles and the gamma-ray profiles. There is growing evidence for the existence of a new class of isolated neutron stars with ultra-strong magnetic fields that includes soft gamma-ray repeaters (SGRs) in which photon splitting and Compton scattering play a significant role in the magnetospheric physics. As in the previously accomplished work for Compton scattering in the polar cap model, the team will develop magnetic Compton scattering required in these near or supra critical magnetic fields applicable to the SGR environments.
These projects have broad impacts primarily on the education of undergraduate students by providing an environment and challenging topics that lead to the enhancement of their knowledge and skills. The PI will take students for a month to Goddard Space Flight Center where the undergraduates will interact with NASA scientists discussing their findings as well as attending talks given in a wide variety of areas of investigation. The students are respected as fellow colleagues in the pursuit of the project and are encouraged to excel. The experience instills in the students the confidence in their quest and encourages them to train and discipline themselves. The students also gain oral and presentation skills as they prepare and present a poster at the end of their summer experience, later presented in a yearly research symposium at Hope College.
