First-principles simulations of pulsar magnetoshpheres pulsars are rotating magnetized neutron STARS which produce broadband pulsed emission. Observations with fermi gamma-RAY space telescope have…

This federal contract award NNX15AM30G was granted by the National Aeronautics and Space Administration (NASA) to The Trustees of Princeton University for research related to "First-Principles Simulations of Pulsar Magnetospheres." The $598,779.33 grant will support Princeton's development of three-dimensional kinetic simulations of pulsar magnetospheres using particle-in-cell methods. The research aims to produce self-consistent models of pulsar plasma supply and magnetospheric structure, enabling the calculation of gamma-ray light curves and spectra to interpret data from the Fermi Gamma-Ray Space Telescope. This grant does not have a set-aside designation. Princeton University is the prime contractor and will likely collaborate with other academic institutions, though no major subcontractors were specified.

First-principles simulations of pulsar magnetoshpheres pulsars are rotating magnetized neutron STARS which produce broadband pulsed emission. Observations with fermi gamma-RAY space telescope have uncovered more than 100 gamma-RAY emitting pulsars, dramatically expanding the number of such sources known, and producing unprecedented data on light curves and spectra in the gamma-RAY band. The magnetospheric processes that lead to this emission are very interesting and currently not understood in detail. The main difficulty is the absence of a self-consistent model of the pulsar magnetosphere that can predict the global shape of the magnetic field and the state of the plasma throughout the magnetosphere. The standard picture envisions the magnetosphere as filled with plasma due to space-charge-limited flow of charges from the surface of the star. These charges are accelerated by strong electric fields induced by rapid stellar rotation. As charges are curved while traveling along the magnetic fields, they emit curvature radiation which can pair-produce and fill the magnetosphere with pair plasma. The currents and charges in this plasma affect magnetic field structure and particle acceleration. Until recently, no self-consistent solutions of the pulsar electrodynamics that accounted for plasma supply and production existed. Considerable progress on the global magnetospheric structure was made under assumptions about the plasma supply in the force-free and magnetohydrodynamic limits, which assume abundant plasma throughout the magnetosphere. These solutions allowed to calculate the global structure of oblique rotators and their spin-down power at the expense of losing information about particle density and acceleration, and making IT difficult to compute emision spectra. Recently, the development of multidimensional kinetic simulations has brought the goal of self-consistently calculating palsma supply and magnetospheric shape of pulsars closer to reality. In this proposal, we plan to perform first three-dimensional kinetic simualtions of pulsar magnetospheres using particle-in-cell (PIC) method. PIC is an established technique for plasma simulations that represents the plasma as charged macroparticles that are advanced in electromagnetic fields. The fields are evolved with particle currents as sources, completing the cycle. We recently demonstrated that self-consistent PIC simulations with particle extraction from the star and pair production in the magnetosphere lead to solutions which resemble the force-free state, but carry information about particle acceleration and beaming. We will perform a numerical survey of pulsar magnetospheres with a multitude of pair production prescriptions in order to ascertain the regimes of pulsar parameter space where magnetospheres with abundant plasma occur. Further, we will use the plasma distribution function from these simulations to calculate the gamma-RAY light curves and phase-resolved spectra, comparing them with our previous work on emission from force-free magnetic geometries. These results will be applied to interpret the library of pulsar light curves from fermi. 45 years after discovery of pulsars, the study of pulsar magnetospheres is now undergoing an exciting transformation, where a calculable standard model is being formulated. The advent of global kinetic simulations that we will utilize in this research will enable US to produce the first complete abinitio models of pulsar magnetospheres and their emission, solving one of the oldest unsovled problems in astophysics.