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Vertical Structure and Temporal Variation of Auroral H₃⁺ at Jupiter

Presentation #324.06 in the session Giant Planet Magnetospheres, Ionospheres and Aurorae (Poster)

Published onOct 23, 2023
Vertical Structure and Temporal Variation of Auroral H₃⁺ at Jupiter

The dominant molecular ion in Jupiter’s ionosphere, H3+, is an efficient radiator that can be readily observed at NIR wavelengths using ground-based telescopes. Temperatures and densities of ionospheric H3+ are representative of the energetic and dynamic drivers of the upper atmosphere, and have been leveraged to study the complicated magnetosphere-ionosphere-atmosphere coupling processes at work in the system since H3+ emissions were first detected in Jupiter’s auroral region more than 30 years ago.

Prior remote studies of H3+ have largely been focused on mapping column-integrated temperatures and densities above the disk. Here, using observations from Keck/NIRSPEC obtained in conjunction with Juno perijoves in 2022, we instead present a series of profiles of H3+ in altitude above Jupiter’s active aurorae. These preliminary results find substantial spatiotemporal variations in temperature. For the periods sampled, the northern auroral limb profiles exhibit a much higher temperature, with peak values up to 1700 K and at a mean peak altitude of 1100 km above the limb, whereas the southern auroral temperatures were approximately 1000 K with a slightly lower altitude peak. Differences in northern and southern H3+ densities are more muted. These results provide important constraints on the processes governing temperatures in Jupiter’s upper atmosphere and insight into vertical ionospheric structure in the auroral region. This campaign of ground-based support for the Juno mission using Keck continues through the 2023B semester, so upcoming H3+ limb profiles will further constrain longer-term variability in conjunction with Juno observations.

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