Pulsar Magnetospheres
Magnetospheres of rotating neutron stars, pulsars, allow studying a wide range of physics under extreme conditions. The observed radiation from neutron stars is emitted by plasma which is produced close to the neutron star surface, in a process resembling a lightning. It involves intense acceleration of electrons, emission of energetic photons and their quantum-electrodynamical decay into electron-positron pairs in extreme magnetic fields of a neutron star. Efficiency of these unique anti-matter factories sets radiative signatures of neutron stars, determines the abundance of galactic cosmic-ray positrons and may even provide clues for physics beyond the Standard Model (i.e., by sourcing light axions — hypothetical particle that is a Dark Matter candidate).
Our group applies first-principles particle-in-cell plasma simulations to unravel long-standing mysteries of electromagnetic radiation produced by pulsars. Recent work targeted understanding the coherent radio emission mechanism (paper 1, paper 2, paper 3), particle acceleration and production of gamma-ray emission in magnetospheric current sheet (paper 4, paper 5) and polarization of X-ray emission (in preparation).
Our current understanding is summarized in the Annual Review article: Philippov & Kramer (2022).
Time-dependent physics in the pulsar magnetosphere. (a): 3D PIC simulation of the global pulsar magnetosphere. The zoom box highlights an example X-point, where magnetic field lines break and reconnect. The dense structures in the current sheet correspond to 3D plasmoids, or flux ropes, with an example magnetic field line wrapping around the plasmoid shown right next to the X-point. (b): Slice through the 3D PIC simulation of the magnetosphere of an aligned rotator, which shows the plasmoid unstable current sheet. (c) 2D PIC simulation of the reconnecting current sheet. (d) 2D PIC simulation of the pair lightning.
