A Survey of Small-Scale Waves and Wave-Like Phenomena in Jupiter's Atmosphere Detected by JunoCam

Abstract

In the first 20 orbits of the Juno spacecraft around Jupiter, we have identified a variety of wave-like features in images made by its public-outreach camera, JunoCam. Because of Juno's unprecedented and repeated proximity to Jupiter's cloud tops during its close approaches, JunoCam has detected more wave structures than any previous surveys. Most of the waves appear in long wave packets, oriented east-west and populated by narrow wave crests. Spacing between crests were measured as small as 30 km, shorter than any previously measured. Some waves are associated with atmospheric features, but others are not ostensibly associated with any visible cloud phenomena and thus may be generated by dynamical forcing below the visible cloud tops. Some waves also appear to be converging, and others appear to be overlapping, possibly at different atmospheric levels. Another type of wave has a series of fronts that appear to be radiating outward from the center of a cyclone. Most of these waves appear within 5°of latitude from the equator, but we have detected waves covering planetocentric latitudes between 20°S and 45°N. The great majority of the waves appear in regions associated with prograde motions of the mean zonal flow. Juno was unable to measure the velocity of wave features to diagnose the wave types due to its close and rapid flybys. However, both by our own upper limits on wave motions and by analogy with previous measurements, we expect that the waves JunoCam detected near the equator are inertia-gravity waves.Plain Language Summary JunoCam, the visible camera on the Juno spacecraft orbiting Jupiter, has detected hundreds of small-scale waves and wave-like features, some as small as 30 km, shorter than ever measured before. Some waves appear near larger features, which may be associated with their origin, but others must be the result of winds hidden beneath the clouds. Most of the waves appear like long trains of narrow, parallel lines, but there is a wide variety of other types of wave-like features. Some waves converge on each other or cross over each other, and some wavefronts appear to radiate outward from a hurricane-like storm. Although waves are found over a wide range of latitudes from 20°S to 45°N, the overwhelming majority are found in a narrow band between 5°S and 5°N. The vast majority of these features are found at latitudes with strong prevailing eastward winds, heading in the same direction as Jupiter's rotation. The lack of motion associated with waves at the equator and their similarity to waves measured over even longer time spans by previous spacecraft imply that they are like ripples in a pond but in a rotating fluid, a phenomenon known as inertia-gravity waves.

Jovian sodium nebula and Io plasma torus S$^+$ and brightnesses 2017 – 2023: insights into volcanic vs.\ sublimation supply

“…In particular, nearly all of the plasma found in Jupiter's magnetosphere comes from Io and makes its way through the IPT in 20 -80 days before rapidly spiraling out through the rest of the magnetosphere Hess et al, 2011;Copper et al, 2016;Tsuchiya et al, 2018). The modulations seen in the lower panel of Figure 4 therefore precede modulation in plasma density throughout the Jovian magnetosphere, a feature that can be used to enhance the science operations of the Juno mission (Bolton et al, 2017) and supporting observations (Orton et al, 2020(Orton et al, , 2022). NASA's Europa Clipper (Howell & Pappalardo, 2020)…”

“…Once material has left the IPT, it rapidly spirals outward in a few days . Thus, long-term monitoring of the IPT, such as that presented here, provides critical context to any study of Jupiter's broader magnetosphere, such as that conducted by NASA's Juno mission (Bolton et al, 2017) and supporting observations (Orton et al, 2020(Orton et al, , 2022.…”

“…We anticipate the IoIO data will be very useful for correlative studies for observations focusing on Io and the effect that material escaping Io has on Jupiter's magnetosphere, such as afforded by NASA's Juno mission (Bolton et al, 2017) and supporting observations (Orton et al, 2020(Orton et al, , 2022. To that effect, the surface brightness points shown in Figure 4 have been archived at Zenodo (Morgenthaler et al, 2023).…”

Jupiter's Overturning Circulation: Breaking Waves Take the Place of Solid Boundaries

“…Since the EMF eddies are accelerating both the eastward and westward jets, it is natural to assume that the phase speeds c of the waves are similarly bounded by the jet speeds. Most of the mesoscale waves, which have wavelengths around 300 km, are inertia‐gravity waves (Orton et al., 2020), and they satisfy this criterion—their phase speeds are <50% and often <10% of the zonal flow speeds, regardless of direction (Arregi et al., 2009; Hunt & Muller, 1979; Orton et al., 2020; Simon et al., 2015). So, we choose a reference frame that has eastward jets on the poleward sides of the zones and westward jets on their equatorward sides, and we assume c = 0 in that frame.…”

A Survey of Small‐Scale Waves and Wave‐Like Phenomena in Jupiter's Atmosphere Detected by JunoCam

“…The map can also be referenced directly via Wong (2017). The values of the measurements shown in Figures 16 and 17 are displayed in a table in Section SI2 of the supporting information, and they can be accessed via Orton (2020). We note that preliminary results, including a version of Figure 11, were included in a NASA press release: https://www.jpl.nasa.gov/news/news.php?feature=7264.…”