Particle Transport in Pulsar Halos and Their Contribution to the Diffuse Galactic Gamma-ray Emission

Abstract

In this contribution, we discuss the particle transport mechanism in pulsar halos. The isotropic diffusion model requires a feasible way of generating strong turbulence in the ambient interstellar medium. The streaming instability driven by escaping electron/positron pairs is not sufficient, but it might work with certain pre-amplification of the turbulence. The anisotropic diffusion model predicts many pulsar halos with elongated morphology, which are currently not detected. We demonstrate that those elongated halos are difficult for detection, but long-term exposure of LHAASO may discover some of them, which may serve as a critical test of the model. Finally, we show that pulsar halos, with either model, may have important contribution to the diffuse Galactic gamma-ray emission (DGE).