Fig. 6: Schematic illustration of the generation mechanism for AKR precursors and auroral beads (Wave-like aurora).
From: Radio emissions reveal Alfvénic activity and electron acceleration prior to substorm onset
a Overview of the global process: dispersive Alfvén waves (white background wavy lines) accelerate electrons, stimulating double-layer structures (two parallel arrowed lines along magnetic field lines). These accelerated electrons precipitate along magnetic field lines, producing auroral beads in the ionosphere. Simultaneously, the earthward movement of the double layers generates the frequency-drifting AKR emissions. The bead's wavelength plotted in the ionosphere roughly corresponds to the spatial wavelength of the DAWs in the magnetosphere according to the previous study. b Example of auroral beads observations captured at the Muonio station. c Typical AKR precursor observations from the Polar PWI instrument, showing frequency-drifting tones indicated by the white dashed lines. Source data are provided as a Source Data file.
