First-Principles Modeling of Pulsar Multi-Wavelength Emission

Pulsars, which are rapidly rotating, strongly magnetized neutron stars emitting pulsed multi-wavelength radiation, present some of the universe's most extreme environments. These objects combine the effects of relativistic plasma physics, ultra-strong magnetic fields, nonlinear quantum electrodynamics, and general relativity. Despite more than five decades of observational data on over 2,000 known pulsars, many open questions remain regarding how they produce their broadband radiation. Among these questions, the mechanism of their radio emission is one of the most famous unsolved problems in astrophysics. Leveraging current multi-wavelength observational coverage and unprecedented computing power, a research team at Washington University in St. Louis will work toward answering these questions using direct numerical simulations. Extreme objects such as pulsars are excellent topics to capture the curiosity of students and the general public. For undergraduate and graduate students, studying these objects gives them excellent training in analyzing complex physical phenomena. For the public, these extreme objects can conjure their deep curiosity and may persuade more people to engage in STEM-related activities or pursue a career related to physics or astrophysics. To achieve this cultural influence, the team will mentor students, participate in community events in St. Louis, and organize a high energy astrophysics summer school. This work will provide a unified theoretical model of the pulsar emission mechanism, directly connecting plasma physics processes with observational data. The project will take a two-pronged approach based on first-principles plasma simulations to systematically understand how pulsar physics leads to observational signals. First, the team will study local radiation and plasma microphysics that lead to the emission of radio signals as well as very high-energy gamma-rays. Then they will study how the global structure of the pulsar magnetosphere determines its multi-wavelength light curve and develop a model to infer physical properties based on observational data at all wavelengths. The study will also provide key insights into other branches of physics: it will inform model builders to better constrain the nuclear equation of state within a neutron star; it will give us better understanding of relativistic plasma physics in such extreme environments; it can also constrain physics beyond the Standard Model and probe parameter spaces for dark matter particle candidates. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.