Experimental measurements of the large-scale anisotropy of Galactic cosmic rays (CRs) reveal a sharp change in the phase of the dipole component at energies around 100 TeV. Most traditional interpretations invoke macroscopic diffusion models of CR propagation or the influence of nearby sources; however, such approaches often do not adequately account for the local magnetic-field structure at the observer, which can substantially distort the measured anisotropy. Here we treat the anisotropy as a generic consequence of the local magnetic-field properties and the particle transport regime and therefore expect it to manifest at arbitrary locations in the Galaxy, rather than being specific to the vicinity of the Solar System. The source distribution and the local field parameters primarily determine the characteristic energy and the width of the dipole-phase transition region.

In this work, we model CR transport microscopically by numerically integrating particle trajectories in an interstellar magnetic field represented as the superposition of a uniform regular component and an isotropic turbulent component with a Kolmogorov spectrum. The turbulent field is generated using a harmonic method. The anisotropy is computed using the backtracking method to construct a sky map of the arrival intensity, followed by a multipole decomposition and extraction of the dipole term. We show that the sharp phase change is naturally associated with a crossover in the propagation regime. At energies where the Larmor radius is smaller than the turbulence correlation length, particles remain tied to local field lines and the dipole phase aligns with the local magnetic-field direction. Once the Larmor radius exceeds the correlation length, transport approaches standard three-dimensional diffusion, and the phase stabilizes along the direction set by the large-scale regular field. Our numerical results indicate that the position and the width of the phase-transition region are determined primarily by this transport-regime crossover.