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Simultaneous Multi-wavelength Radiative Transfer Modeling of Jovian Hot Spots and Ammonia Plumes with HST UVIS and Keck NIRSPEC

Presentation #205.02 in the session Vortices and Plumes on Jupiter.

Published onOct 20, 2022
Simultaneous Multi-wavelength Radiative Transfer Modeling of Jovian Hot Spots and Ammonia Plumes with HST UVIS and Keck NIRSPEC

We present jointly-fitted visible/near-infrared and thermal infrared radiative transfer (RT) models of six hot spots and ammonia (NH3) plumes found in Jupiter’s North Equatorial Belt (NEB) in January 2017. Hot spots are downwelling regions of the Jovian atmosphere that appear bright in the thermal infrared and dark at visible wavelengths, owing to a combination of low cloud opacities and volatile abundances. They open a window into Jupiter’s deeper atmospheric layers, which are normally obscured by overlying clouds. Conversely, NH3 plumes are upwelling regions with thick overlying clouds and high NH3 abundances, which appear bright at visible wavelengths and dark in the thermal infrared. NH3 is a tracer of atmospheric dynamics, so studying these alternating NH3-rich and -poor regions is important for understanding the dynamics that drive Jupiter’s atmosphere. Our dataset contains observations from seven Hubble Space Telescope (HST) UVIS filters between 0.3-0.9μm and three wavelength windows from Keck II’s NIRSPEC instrument between 4.6-5.3μm. HST observations are sensitive to atmospheric conditions between the tropopause at 0.1 bar down to the uppermost opaque cloud tops, which can range from 0.7-5 bar. Our NIRSPEC observations are sensitive to pressures between 2-7 bar depending on the opacities of the NH3-ice, NH4SH, and H2O-ice clouds. We combine these two datasets to determine the structure and composition of Jupiter’s hot spots and NH3 plumes from 0.1-7 bar, using our in-house RT modeling package, SUNBEAR, to model the extent and thickness of the tropospheric hazes, the location and structure of Jupiter’s clouds, and the abundances of volatiles such as NH3, H2O, and PH3. We find hot spots covering a range of radiances are all devoid of NH4SH and H2O-ice clouds, and instead have their relative brightnesses scaled by the combined opacity of the NH3-ice cloud and upper tropospheric aerosols. NH3 and H2O abundances vary by a factor of ~2-4 between our brightest and dimmest hot spots, and are depleted relative to NEB background models. Our NH3 plume models find high opacity NH3-ice, NH4SH, and H2O-ice clouds along with thick upper tropospheric aerosols, with higher volatile abundances relative to background models.

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