Polar Cap Boundary Layer waves are ELF/VLF electric and magnetic waves detected on field lines adjacent to the polar cap, thus their name. Waves are present at this location 96% of the time. The wave latitude-local time distribution is shown to be the same as that of the auroral oval. The most intense waves are detected coincident with the strongest magnetic field gradients (field-aligned currents). Specific frequency bands of whistler mode-waves are identified: ~200 Hz, 1-2 kHz and ~5 kHz. Two types of intense electric waves are present: Solitary bipolar pulses (electron holes) and ~kHz electric turbulence. The PCBL waves are most likely a consequence of auroral zone field-aligned current instabilities. The currents have in turn been ascribed to be due to magnetospheric convection driven by the solar wind.
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