Magnetars are young, highly magnetized neutron stars. Interactions between the strong magnetic fields, the dense neutron star material, and the hot plasma surrounding the magnetar can drive intense bursts of X-ray and radio emission and sustain the production of high-energy X rays. A research group at Dartmouth College will develop quantitative, self-consistent models of plasma flows around magnetars, enabling direct comparisons to observations. Understanding emission from these objects will provide a unique probe into extreme physics and provide insight into some of the universe’s most energetic processes. The research program also includes a comprehensive educational and outreach program to foster STEM education and public engagement in computational high-energy astrophysics. This project combines novel theoretical concepts about quantum electrodynamics (QED) reactions in super-Schwinger magnetic fields with innovative numerical tools to provide unprecedented insights into the plasma dynamics of magnetar magnetospheres. Advanced particle-in-cell (PIC) simulations using the ENTITY code will synthesize angularly dependent spectra of energetic photons escaping the magnetosphere, directly comparable to observed magnetar X-ray activity. The project has four main goals: (1) build an efficient infrastructure for modeling radiation-rich magnetar magnetospheres, (2) investigate different strong-field QED reactions capable of sustaining the magnetar circuit, including resonant