Аннотация:Magnetic perturbations in the topside auroral ionosphere observed by the FAST satellite in the events of broadband extra low frequency (BB ELF) turbulence are investigated at frequencies 0.5-8 Hz (scales from 14 km down to 0.9 km). The power-law scaling and peculiar polarization patterns of the perturbations are highlighted. By comparing with the magnetic fields simulated according to the Chang et al. (2004) scenario of coarse-graining process development, we demonstrate that the magnetic perturbations observed in the events of the BB ELF turbulence can be reasonably understood in terms of non-linearly interacting multiscale field-aligned currents traversed by the spacecraft.