Particle-in-Cell Simulations of the Twisted Magnetospheres of Magnetars. I

Journal Article · Tue Aug 01 04:00:00 EDT 2017 · Astrophysical Journal

DOI:https://doi.org/10.3847/1538-4357/AA7A57· OSTI ID:22875971

Chen, Alexander Y.; Beloborodov, Andrei M. ^[1]

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1. Physics Department and Columbia Astrophysics Laboratory, Columbia University, 538 West 120th Street New York, NY 10027 (United States)

The magnetospheres of magnetars are believed to be filled with electron–positron plasma generated by electric discharge. We present a first numerical experiment demonstrating this process in an axisymmetric magnetosphere with a simple threshold prescription for pair creation, which is applicable to the inner magnetosphere with an ultrastrong field. The e{sup ±} discharge occurs in response to the twisting of the closed magnetic field lines by a shear deformation of the magnetar surface, which launches electric currents into the magnetosphere. The simulation shows the formation of an electric “gap” with an unscreened electric field (E⋅B≠0) that continually accelerates particles along the magnetic field lines and sustains pair creation. The accelerating voltage is self-regulated to the threshold of the e{sup ±} discharge. It controls the rate of energy release and the lifetime of the magnetic twist. The simulation follows the global evolution of the twisted magnetosphere over a long time and demonstrates its gradual resistive untwisting. A vacuum cavity forms near the star and expands, gradually erasing magnetospheric electric currents j. The active j-bundle shrinks with time and its footprints form shrinking hot spots on the magnetar surface bombarded by the created particles.

• OSTI ID: 22875971
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 844; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
AXIAL SYMMETRY
COMPUTERIZED SIMULATION
ELECTRIC DISCHARGES
ELECTRIC FIELDS
ELECTRON-POSITRON INTERACTIONS
HOT SPOTS
MAGNETIC FIELDS
NEUTRON STARS
PAIR PRODUCTION
PLASMA
RELATIVISTIC RANGE