NCCS and NAS Enable ‘Pulsar in a Box’ Simulations

NASA Center for Climate Simulation (NCCS) and NASA Advanced Supercomputing (NAS) Facility supercomputers enabled groundbreaking simulations of spinning neutron stars—called pulsars—that trace the paths of charged particles in magnetic and electric fields surrounding the stars.

Goddard Space Flight Center (GSFC) and University of Milan astrophysicists ran more than 1,000 simulations to experiment with the effects of changing numerical and physical parameters. Each ‘pulsar in a box’ simulation with the team’s own C-3PA particle-in-cell (PIC) software code included between 100 million and 1 billion particles.

The simulations used from 1,728 to 4,096 cores on the NCCS Discover and NAS Pleiades supercomputers, with the longest run lasting 2 days. The scientists also leveraged several terabytes of online disk storage, VisIt visualization software, and consulting services for installing and using specific libraries.

A ‘pulsar in a box’ simulation tracks the fate of electrons (blue) and antimatter positrons (red) as they interact with powerful magnetic and electric fields around a neutron star. Lighter tracks indicate higher particle energies. Each particle seen here actually represents trillions of electrons or positrons. Visualization by Tom Bridgman, GSFC Scientific Visualization Studio.

Among other results, the computations reveal that antimatter positron particles flow out from the pulsar’s lower latitudes to form a thin current sheet. The continuous flow of positrons accelerating in the current sheet can generate the gamma-ray pulses observed by NASA’s Fermi Gamma-ray Space Telescope.

“The pulsar magnetosphere is a continuous interaction between electromagnetic fields and particle motions,” said Constantinos Kalapotharakos, an assistant research scientist affiliated with GSFC’s Astrophysics Science Division and the University of Maryland, College Park. The best way to study this system is by self-consistent methods like PIC methods, which require enormous computational power. Thanks to NASA supercomputing resources, we can now run realistic simulations that uncover some of the pulsar mysteries.”

More Information

‘Pulsar in a Box’ Reveals Surprising Picture of a Neutron Star’s Surroundings

Brambilla, G., C. Kalapotharakos, A.N. Timokhin, A.K. Harding, and D. Kazanas, 2018: Electron–Positron Pair Flow and Current Composition in the Pulsar Magnetosphere, Astrophysical Journal, 858, 81, doi:10.3847/1538-4357/aab3e1.