Current closure through the neutron star crust. (arXiv:1903.05093v1 [astro-ph.HE])
<a href="http://arxiv.org/find/astro-ph/1/au:+Karagergopoulos_V/0/1/0/all/0/1">V. Karagergopoulos</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gourgouliatos_K/0/1/0/all/0/1">K.N. Gourgouliatos</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Contopoulos_I/0/1/0/all/0/1">I. Contopoulos</a>
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.
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.
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