Project: PULSAR - Plasma physics of ultra high fields in neutron stars

Prace Call: 17th
ID: 2018184464, Leader: Luis Silva
Affiliation: Instituto Superior Tecnico, PT
Research Field: Fundamental Constituents of Matter
Collaborators: Marija Vranic Instituto Superior Tecnico PT , Thomas Grismayer Instituto Superior Tecnico PT , Kevin Schoeffler Instituto Superior Tecnico PT , Fabio Cruz Instituto Superior Tecnico PT , Fabrizio Del Gaudio Instituto Superior Tecnico PT
Resource Awarded: 40 Mil. core hours on MareNostrum

Abstract

How are electron-positron pair plasmas generated at the polar cap of pulsars? How does the produced pair contribute to feeding the pulsar magnetosphere? What are the expected radiation signatures? These are prominent scientific questions where plasma astrophysics is intimately connected with quantum electrodynamics. This proposal aims to exploit the outstanding computing facilities provided by PRACE to address these compelling challenges by leveraging on the pioneered advances in coupling quantum electrodynamics effects with particle-in-cell simulations. The main scientific route to answer some of these questions consists in understanding the coupling of the pair production region with the global field organization of the pulsar magnetosphere. In particular, it is crucial to assess self-consistently the dependence of the pair multiplicity at the polar cap on the global magnetic field topology and vice versa. This task requires a special computational effort given the separation of the scales involved, namely the macroscopic size of the magnetosphere down to the plasma kinetic and quantum electrodynamics scales. The first goal of this research project is to study the production of pair plasma via cascades that occur in a localized portion of the magnetosphere around the polar cap of pulsars. The second goal is to model the global pulsar magnetosphere, leveraging on the knowledge coming from the first task. The self-consistent study of the interdependence among the plasma dynamics pertinent to such different spatial and temporal scales is difficult and massively parallel kinetic particle-in-cell simulations are critical to establishing this bridge. The unique computational infrastructures provided by PRACE would be critical to explore some of the most exciting fundamental physics questions at the forefront of science identified in this proposal. This project will leverage on the massively parallel, fully relativistic particle-in-cell code OSIRIS, which includes a set of dedicated modules to study the development of pair cascades at the polar cap of pulsars and their global magnetosphere. These are (i) a QED module for photon emission and pair creation, (ii) a merging module for withstanding the exponential increase of macro-particles in the cascades, (iii) a Compton collisional module for the accounting of direct exchange of energy between photons and electron-positron pairs, and (iv) a spherical coordinates module for modeling the global magnetosphere. This research route embraces the spirit and the path outlined by the ERC advanced grant in Pairs, which aims at understanding the dynamics of electron-positron pair plasmas in extreme fields. Many steps were already taken in this direction, and our numerical infrastructure is now ready to be massively employed in studying some of the most puzzling but marvelous questions in plasma astrophysics