  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.
