The ionospheric response to auroral precipitation at the giant planets is reviewed,
using models and observations. The emission processes for aurorae at radio, infrared, visible,
ultraviolet, and X-ray wavelengths are described, and exemplified using ground- and
space-based observations. Comparisons between the emissions at different wavelengths are made, where possible, and interpreted in terms of precipitating particle characteristics or
atmospheric conditions. Finally, the spatial distributions and dynamics of the various components
of the aurorae (moon footprints, low-latitude, main oval, polar) are related to magnetospheric
processes and boundaries, using theory, in situ, and remote observations, with
the aim of distinguishing between those related to internally-driven dynamics, and those
related to the solar wind interaction.