Magnetic mirroring and curvature scattering cause anomalous cosmic-ray transport

We study the transport of test particles in anisotropic magnetohydrodynamic turbulence. In the regime of large fluctuations, the turbulence develops coherent structures and intermittency. Coherent field line bundles can act as magnetic mirrors and localized patches with sharp field line curvature can intermittently break magnetization of test particles. We record magnetic moment variations and experienced field line curvature around pitch-angle reversals. We find that both mechanisms (magnetic mirroring and curvature scattering) govern parallel transport via pitch-angle reversals, which occur with power-law distributed waiting times and can be modeled as a Lévy walk, while classical gyro-resonance only plays a minor role. Further, perpendicular transport is either enhanced by curvature scattering in synergy with chaotically separating field lines or diminished by magnetic mirroring due to confinement in coherent field line bundles. For strongly magnetized particles, most reversal events are caused by magnetic mirroring, while curvature scattering additionally acts on particles with small pitch angles that fall in the loss cones of most magnetic mirrors. Finally, we discuss how energy-independent transport coefficients may arise in structured intermittent turbulence.