Radio polarisation of millisecond pulsars with multipolar magnetic fields

NICER has observed a few millisecond pulsars where the geometry of the X-ray emitting hotspots on the neutron star is analyzed in order to constrain the mass and radius from X-ray light curve modeling. One example, PSR J0030+0451, is shown to possibly have significant multipolar magnetic fields at the stellar surface. Using force-free simulations of the magnetosphere structure, it has been shown that the radio, X-ray, and gamma-ray light curves can be modeled simultaneously with appropriate field configuration. An even more stringent test is to compare predictions of the force-free magnetosphere model with observations of the radio polarization. This paper attempts to reproduce the radio polarization of PSR J0030+0451 using a force-free magnetospheric solution. As a result of our modeling, we can reproduce certain features of the polarization well.