Galileo Images of Lightning on Jupiter

Little, Blane; Anger, C. D.; Ingersoll, Andrew P.; Vasavada, A. R.; Senske, D. A.; Breneman, H.; Borucki, W. J.

doi:10.1006/icar.1999.6195

Cited by 140 publications

(139 citation statements)

References 31 publications

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“…Schneider and Liu (2009) and Liu and Schneider (2010) also find a broad polar cyclone that precesses around the pole in a spherical shell that extends in pressure to 3 bars. The model used in the present work is the first to force a polar domain with small thermal perturbations that mimic observed moist convection in size, strength, and duration, motivated by abundant observations of intense moist convection on the gas giants (Little et al 1999;Gierasch et al 2000;Li et al 2004).…”

Section: Beta Drift On Earth and Giant Planetsmentioning

confidence: 99%

Weak Jets and Strong Cyclones: Shallow-Water Modeling of Giant Planet Polar Caps

O’Neill

Emanuel

Flierl

2016

Journal of the Atmospheric Sciences

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Giant planet tropospheres lack a solid, frictional bottom boundary. The troposphere instead smoothly transitions to a denser fluid interior below. However, Saturn exhibits a hot, symmetric cyclone centered directly on each pole, bearing many similarities to terrestrial hurricanes. Transient cyclonic features are observed at Neptune's South Pole as well. The wind-induced surface heat exchange mechanism for tropical cyclones on Earth requires energy flux from a surface, so another mechanism must be responsible for the polar accumulation of cyclonic vorticity on giant planets. Here it is argued that the vortical hot tower mechanism, claimed by Montgomery et al. and others to be essential for tropical cyclone formation, is the key ingredient responsible for Saturn's polar vortices. A 2.5-layer polar shallow-water model, introduced by O'Neill et al., is employed and described in detail. The authors first explore freely evolving behavior and then forceddissipative behavior. It is demonstrated that local, intense vertical mass fluxes, representing baroclinic moist convective thunderstorms, can become vertically aligned and accumulate cyclonic vorticity at the pole. A scaling is found for the energy density of the model as a function of control parameters. Here it is shown that, for a fixed planetary radius and deformation radius, total energy density is the primary predictor of whether a strong polar vortex forms. Further, multiple very weak jets are formed in simulations that are not conducive to polar cyclones.

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Section: Beta Drift On Earth and Giant Planetsmentioning

confidence: 99%

Weak Jets and Strong Cyclones: Shallow-Water Modeling of Giant Planet Polar Caps

O’Neill

Emanuel

Flierl

2016

Journal of the Atmospheric Sciences

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“…However, with the excep-tion of a recent quasigeostrophic study by Li et al (2006), numerical models with realistic thunderstorm turbulence have not been performed. On Jupiter and Saturn, thunderstorms are localized, episodic, and cover only a small fraction (Ͻ1%) of the planet's area (Little et al 1999;Porco et al 2003). In contrast, most two-dimensional turbulence studies use random forcing that occurs everywhere simultaneously and is confined to a small range of wavenumbers.…”

Section: Introductionmentioning

confidence: 99%

Numerical Simulations of Forced Shallow-Water Turbulence: Effects of Moist Convection on the Large-Scale Circulation of Jupiter and Saturn

Showman

2007

Journal of the Atmospheric Sciences

109

140

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To test the hypothesis that the zonal jets on Jupiter and Saturn result from energy injected by thunderstorms into the cloud layer, forced-dissipative numerical simulations of the shallow-water equations in spherical geometry are presented. The forcing consists of sporadic, isolated circular mass pulses intended to represent thunderstorms; the damping, representing radiation, removes mass evenly from the layer. These results show that the deformation radius provides strong control over the behavior. At deformation radii Ͻ2000 km (0.03 Jupiter radii), the simulations produce broad jets near the equator, but regions poleward of 15°-30°latitude instead become dominated by vortices. However, simulations at deformation radii Ͼ4000 km (0.06 Jupiter radii) become dominated by barotropically stable zonal jets with only weak vortices. The lack of midlatitude jets at a small deformation radii results from the suppression of the beta effect by column stretching; this effect has been previously documented in the quasigeostrophic system but never before in the full shallow-water system. In agreement with decaying shallow-water turbulence simulations, but in disagreement with Jupiter and Saturn, the equatorial flows in these forced simulations are always westward. In analogy with purely two-dimensional turbulence, the size of the coherent structures (jets and vortices) depends on the relative strengths of forcing and damping; stronger damping removes energy faster as it cascades upscale, leading to smaller vortices and more closely spaced jets in the equilibrated state. Forcing and damping parameters relevant to Jupiter produce flows with speeds up to 50-200 m s Ϫ1 and a predominance of anticyclones over cyclones, both in agreement with observations. However, the dominance of vortices over jets at deformation radii thought to be relevant to Jupiter (1000-3000 km) suggests that either the actual deformation radius is larger than previously believed or that three-dimensional effects, not included in the shallow-water equations, alter the dynamics in a fundamental manner.

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“…Juno will thread magnetic field lines which pass through latitudes in which lightning has been detected by Voyager and Galileo, typically near ∼ 50 • jovigraphic latitude (Little et al 1999). Because Juno will be close to the lightning source in a strong magnetic field, the dispersion will be small, since this is a function of the electron density integrated along the ray path of the whistlers.…”

Section: Lightningmentioning

confidence: 99%

The Juno Waves Investigation

et al. 2017

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Jupiter is the source of the strongest planetary radio emissions in the solar system. Variations in these emissions are symptomatic of the dynamics of Jupiter's magnetosphere and some have been directly associated with Jupiter's auroras. The strongest radio emissions are associated with Io's interaction with Jupiter's magnetic field. In addition, plasma waves are thought to play important roles in the acceleration of energetic particles in the magnetosphere, some of which impact Jupiter's upper atmosphere generating the auroras. Since the exploration of Jupiter's polar magnetosphere is a major objective of the Juno mission, it is appropriate that a radio and plasma wave investigation is included in Juno's payload. This paper describes the Waves instrument and the science it is to pursue as part of the Juno mission.

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Galileo Images of Lightning on Jupiter

Cited by 140 publications

References 31 publications

Weak Jets and Strong Cyclones: Shallow-Water Modeling of Giant Planet Polar Caps

Weak Jets and Strong Cyclones: Shallow-Water Modeling of Giant Planet Polar Caps

Numerical Simulations of Forced Shallow-Water Turbulence: Effects of Moist Convection on the Large-Scale Circulation of Jupiter and Saturn

The Juno Waves Investigation

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