Anisotropic diffusion modeling of cosmic-ray lepton propagation

Abstract

We analyze DAMPE and H.E.S.S. measurements of the total cosmic-ray electron-positron spectrum, together with the AMS-02 positron fraction, using an anisotropic, spatially varying diffusion framework. The diffusion-tensor components are computed via numerical integration of test-particle trajectories in a prescribed Galactic magnetic-field model. We show that simultaneously accounting for the spatial dependence and anisotropy of the diffusion tensor yields an accurate description of the local electron and positron data up to TeV energies. The inferred injection spectral index, $\gamma =2.169$, is fully consistent with expectations from diffusive shock-acceleration theory. In this approach, the observed spectral softening arises naturally from enhanced energy losses experienced by leptons propagating over larger effective distances along the large-scale magnetic field.

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