Polarization of pulsar wind nebulae and millisecond pulsars

The recent IXPE polarization mapping of the Crab and Vela nebulae reveals unexpectedly high polarization degree in large patches of the nebulae. Such a high polarization degree poses a serious challenge to the physical picture that the striped winds from the pulsar are disrupted and dissipated to accelerate particles. Here we present a magnetic reconnection model, where the striped winds are only partially disrupted, leading to high polarization in large patches of the nebulae. The low polarization patches result from the plasmoids produced via magnetic reconnection. Millisecond pulsars can be highly polarized as the pulsar wind nebulae as well. Their polarization signatures are phase-dependent, which can provide crucial information for the geometry and magnetic field of the intra-binary shock. Their spectra, light curves, and polarization can also unravel the particle acceleration in the shock. We present a detailed model of the spectrally and temporally dependent radiation and polarization signatures from millisecond pulsars, based on different geometry and magnetic field structure of the intra-binary shock. Our prediction can be tested with future IXPE and COSI observations.