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Determining the composition and structure of Jupiter’s Lyman-Alpha Airglow from observations by Juno-UVS

Presentation #325.03 in the session Origin and Evolution of Giant Planet Systems I (Poster + Lightning Talk)

Published onOct 23, 2023
Determining the composition and structure of Jupiter’s Lyman-Alpha Airglow from observations by Juno-UVS

Jupiter’s hydrogen (H) airglow emission is created by Lyman alpha (Lyα) photons that are generated when solar photons scatter off of H atoms in the thermosphere. During perijove (PJ), the Juno spacecraft flies through the upper atmosphere about 3500km above the 1-bar level. This permits us to use Juno’s UltraViolet Spectrograph (UVS) to observe the Lyα emission. Juno’s rotation, which has a roughly 30 second period, allows the UVS to see the atmosphere in a wide range from near nadir to near zenith, including the crucial observation range close to the limb where the observed Lyα airglow will be brightest. We present here our methodology in measuring this emission, and the results of several PJ observations selected for their data quality. We will discuss how we account for Juno UVS’s decreasing Lyα sensitivity by calibrating our results with interplanetary Lyα models. We will discuss how determining the brightness as a function of local position, zenith angle, and local time allows us to reach reasonable conclusions about the structure, density, and characteristics of Jupiter’s H atmosphere, as well as potentially explain some of the questions surrounding the Lyα bulge.

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