Abstract
AbstractWe present multiwavelength measurements of the thermal, chemical, and cloud contrasts associated with the visibly dark formations (also known as 5‐μm hot spots) and intervening bright plumes on the boundary between Jupiter's Equatorial Zone (EZ) and North Equatorial Belt (NEB). Observations made by the TEXES 5‐ to 20‐μm spectrometer at the Gemini North Telescope in March 2017 reveal the upper‐tropospheric properties of 12 hot spots, which are directly compared to measurements by Juno using the microwave radiometer (MWR), JIRAM at 5 μm, and JunoCam visible images. MWR and thermal‐infrared spectroscopic results are consistent near 0.7 bar. Mid‐infrared‐derived aerosol opacity is consistent with that inferred from visible‐albedo and 5‐μm opacity maps. Aerosol contrasts, the defining characteristics of the cloudy plumes and aerosol‐depleted hot spots, are not a good proxy for microwave brightness. The hot spots are neither uniformly warmer nor ammonia‐depleted compared to their surroundings at p<1 bar. At 0.7 bar, the microwave brightness at the edges of hot spots is comparable to other features within the NEB. Conversely, hot spots are brighter at 1.5 bar, signifying either warm temperatures and/or depleted NH3 at depth. Temperatures and ammonia are spatially variable within the hot spots, so the precise location of the observations matters to their interpretation. Reflective plumes sometimes have enhanced NH3, cold temperatures, and elevated aerosol opacity, but each plume appears different. Neither plumes nor hot spots had microwave signatures in channels sensing p>10 bars, suggesting that the hot spot/plume wave is a relatively shallow feature.
Highlights
Jupiter’s tropical domain is characterised by two eastward jet streams: the jet at 6.0◦N that separates the red-brown North Equatorial Belt (NEB, 6.0 − 15.1◦N) from the visibly-white Equatorial Zone (EZ, 6.2◦S-6.0◦N); and the jet at 6.2◦S that separates the South Equatorial Belt (SEB, 6.2 − 17.4◦S) from the EZ
Observations made by the TEXES 5-20 μm spectrometer at the Gemini North Telescope in March 2017 reveal the upper-tropospheric properties of 12 hot spots, which are directly compared to measurements by Juno using the Microwave Radiometer (MWR), JIRAM at 5 μm, and JunoCam visible images
We explore whether the dark formations (DFs) and bright MWR-emission are co-located with 5 − μm bright hot spots, and whether we can discern any structure at higher pressures
Summary
Jupiter’s tropical domain is characterised by two eastward jet streams: the jet at 6.0◦N (planetocentric latitude) that separates the red-brown North Equatorial Belt (NEB, 6.0 − 15.1◦N) from the visibly-white Equatorial Zone (EZ, 6.2◦S-6.0◦N); and the jet at 6.2◦S that separates the South Equatorial Belt (SEB, 6.2 − 17.4◦S) from the EZ (see review by Sanchez-Lavega et al, 2019). The region surrounding the NEBs jet at 6.0◦N, both in the northern EZ and the southern NEB, is one of the most longitudinally variable regions on the planet, owing to the existence of an equatorially-trapped Rossby wave on the NEBs jet (Allison, 1990; Showman & Dowling, 2000; Friedson, 2005) This has been thoroughly characterised in visible light, where a chain of ∼ 10 − 13 compact (3000 × 10000 km, Choi et al, 2013), quasi-rectangular, and visibly-dark formations (DFs) spread around the full longitude circle of the NEBs (Vasavada et al, 1998; Arregi et al, 2006; Choi et al, 2013; Rogers, 2019).
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