Accreting Neutron Stars in 3D GRMHD Simulations: Jets, Magnetic Polarity, and the Interchange Slingshot

TL;DR

This study uses 3D GRMHD simulations to explore how magnetic polarity affects accreting neutron stars' jets, disk structure, and outflows, revealing that the star-disk magnetic alignment influences jet power and disk properties.

Contribution

It introduces the concept of the interchange slingshot mechanism and compares the effects of parallel and antiparallel magnetic polarities in neutron star accretion systems.

Findings

Jet power is unaffected when the magnetosphere truncates the disk near or beyond the corotation radius.

Parallel magnetic orientation suppresses jet power and results in a less dense, more magnetized inner disk.

The interchange slingshot mechanism explains the influence of magnetic polarity on disk and jet behavior.

Abstract

Accreting neutron stars differ from black holes by the presence of the star's own magnetic field, whose interaction with the accretion flow is a central component in understanding these systems' disk structure, outflows, jets, and spin evolution. It also introduces an additional degree of freedom, as the stellar dipole can have any orientation relative to the inner disk's magnetic field. We present a suite of 3D general-relativistic magnetohydrodynamic (GRMHD) simulations in which we investigate the two extreme polarities, with the dipole field being either parallel or antiparallel to the initial disk field, in both the accreting and propeller states. When the magnetosphere truncates the disk near or beyond the corotation radius, most of the system's properties, including the relativistic jet power, are independent of the star-disk relative polarity. However, when the disk extends well inside the corotation radius, in the parallel orientation the jet power is suppressed and the inner disk is less dense and more strongly magnetized. We suggest a physical mechanism that may account for this behavior - the interchange slingshot - and discuss its astrophysical implications.