Images of aurorae on Jupiter from H⁺₃ emission at 4 μm

Abstract

SINCE their discovery by Voyager¹, aurorae on Jupiter have been regularly observed over the past ten years, from space at ultraviolet wavelengths² and from the Earth in the thermal infrared band³ (8–13 μm). The ultraviolet emissions originate from H and H₂ in the highest part of the atmosphere, whereas the thermal infrared emissions originate from the stratosphere. Here we present images of near-infrared H⁺₃ emission, recorded simultaneously with high-resolution spectra. Having both imaging and spectral data provides us with a much improved opportunity to study the spatial and spectral characteristics of the H⁺₃ emission. We find that northern and southern emissions show strong spatial variation at the wavelengths of H⁺₃ emission. We suggest that the appearance of the jovian auroral regions at these wavelengths may be explained by a combination of localized H⁺₃ emission, reflection of sunlight by polar haze and stratospheric CH4 emission in the 3.3–3.6 μm range.