Current closure through the neutron star crust

Karageorgopoulos, V; Gourgouliatos, KN; Contopoulos, I

Abstract

Force-free pulsar magnetospheres develop a large-scale poloidal electric current circuit that flows along open magnetic field lines from the neutron star to the termination shock. The electric current closes through the interior of the neutron star where it provides the torque that spins-down the star. In the present work, we study the internal electric current in an axisymmetric rotator. We evaluate the path of the electric current by requiring the minimization of internal Ohmic losses. We find that, in millisecond pulsars, the current reaches the base of the crust, while in pulsars with periods of a few seconds, the bulk of the electric current does not penetrate deeper than about 100 m. The region of maximum spin-down torque in millisecond pulsars is the base of the crust, while in slowly spinning ones it is the outer crust. We evaluate the corresponding Maxwell stresses and find that, in typical rotation-powered radio pulsars, they are well below the critical stress that can be sustained by the crust. For magnetar-level fields, the Maxwell stresses near the surface are comparable to the critical stress and may lead to the decoupling of the crust from the rest of the stellar rotation.

Citation

Karageorgopoulos, V., Gourgouliatos, K., & Contopoulos, I. (2019). Current closure through the neutron star crust. Monthly Notices of the Royal Astronomical Society, 487(3), 3333-3341. https://doi.org/10.1093/mnras/stz1507

• Journal Article Type: Article
• Acceptance Date: May 28, 2019
• Online Publication Date: Jun 3, 2019
• Publication Date: Jun 3, 2019
• Deposit Date: Aug 15, 2019
• Publicly Available Date: Aug 15, 2019
• Journal: Monthly Notices of the Royal Astronomical Society
• Print ISSN: 0035-8711
• Electronic ISSN: 1365-2966
• Publisher: Royal Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 487
• Issue: 3
• Pages: 3333-3341
• DOI: https://doi.org/10.1093/mnras/stz1507
• Public URL: https://durham-repository.worktribe.com/output/1295845