Imaging Jupiter's aurorae from H⁺ ₃ emissions in the 3-4 μm band

SINCE H⁺ ₃ was first spectroscopically detected on Jupiter^1,2, there has been considerable interest in using this simple molecular ion to probe conditions existing in the planet's auroral regions. Here we present a series of images of Jupiter recorded at wavelengths sensitive to emission by H⁺ ₃, which reveal the spatial distribution of excited H⁺ ₃ molecular ions in the jovian ionosphere, as seen from Earth. We believe that they provide high-spatial-resolution images of polar aurorae on Jupiter. They suggest that the intensity of the auroral emission can vary on a timescale of an hour, a shorter period than had previously been noted. We also find that the spatial distribution of H⁺ ₃ emissions correlates only partially with the loci of auroral activity inferred from ultraviolet and longer-wavelength infrared observations. The H⁺ ₃ emission may therefore be controlled by auroral processes that are different from those responsible for the ultraviolet and infrared emissions.