Temporal Variability of the Northern Infrared Aurora of Jupiter as Captured by JWST

We present near-infrared observations of the northern aurora of Jupiter using the NIRSpec instrument on the James Webb Space Telescope, mapping emissions from H+3 and CH4 across the polar region. The data were acquired over a period of ~4 hr, providing a temporally averaged view of these emissions. From the H+3 spectra we derive the temperature of the upper atmosphere and H+3 ion densities. Temperatures are elevated along the main auroral oval at both dawn and dusk, though the highest temperatures recorded were poleward of the main oval at dawn, approaching 1500 K. The highest ion densities were observed dusk-ward of the main oval, closely correlating with the observed H+3 radiance. Using overlapping individual observations (or dithers) we investigate the temporal variability of the temperatures, which we found change too fast to represent wholesale changes to the vertical temperature structure of the upper atmosphere. Instead, these fast changes are likely connected to variable electron precipitation energies, which produce H+3 at different altitudes that sample different parts of the thermospheric temperature profile. The 3.3 μm CH₄ fundamental and hotband emissions are brightest at 210°W close to the pole, which has been seen previously. However, we also see emission along the main oval, suggesting excitation of this non-LTE emission by direct precipitation. Lastly, we suggest that the CH₄ band ratios can be used to trace the penetration depth of the precipitating electrons, and therefore their energies.