PS7.1

Jupiter and Giant Planets: Results from Juno

PS7.1

Jupiter and Giant Planets: Results from Juno

Convener: Scott Bolton | Co-conveners: Michel Blanc, Paul Hartogh, Yamila Miguel

Presentations

| Thu, 26 May, 15:10–18:30 (CEST)

Room D2

Presentations: Thu, 26 May | Room D2

Chairpersons: Scott Bolton, Michel Blanc

Jupiter and Saturn's atmospheres

15:10–15:13

Introduction

15:13–15:19

EGU22-966

ECS

Virtual presentation

Jupiter’s Temperature Structure: A Reassessment of the Voyager Radio Occultation Results

Pranika Gupta, Sushil K. Atreya, Paul G. Steffes, Michael D. Allison, Scott J. Bolton, Leigh N. Fletcher, Tristan Guillot, Ravit Helled, Steven Levin, Cheng Li, Jonathan I. Lunine, Yamila Miguel, Glenn S. Orton, J. Hunter Waite, and Paul Withers

Atmospheric temperature is an important parameter controlled by the outward transport of internal energy and the absorption of solar radiation and auroral heating. It is used widely in models of cloud formation, photochemistry, retrieval of elemental abundances from observations, vertical extrapolation of cloud level winds, and as a boundary condition for interior models. The Galileo probe made very precise in situ measurements of Jupiter’s temperature from the upper atmosphere down to a pressure level of ~22 bars. However, those data correspond to a single location of the probe entry site, which also turned out to be a 5-micron hotspot. Other data covering a wider range of latitude and longitude locations are available from the Voyager radio occultation measurements (Lindal et al. JGR 86, A10, 8721, 1981). The use of S and X bands (2.3 GHz and 8.4 GHz) on Voyager allowed measurements of atmospheric refractivity from approximately 1 millibar to the 1 bar level. However, the temperatures derived from these observations were based on the then-available information on refractivities and composition, which have since been refined. Tabulated data are largely not available and so we have first digitized the data from the published figures of all available Voyager radio occultations and verified their fidelity. We then applied correction factors to the pressures and temperatures based on current laboratory data on radio refractivities of gases relevant to the radio occultation regime (H₂, He, CH₄, PH₃, Ne and Ar) and used the gas abundances measured by the Galileo probe, also accounting for their implied revision of the assumed molecular weight. Depending on the set of radio occultation observations, the corrected temperature is greater by as much as 3 K at the 1-bar level and 6 K at the 1-millibar level compared to the originally published profile (Lindal et al. 1981). Considering all available radio occultation data sets the corrected temperature at the 1-bar level is 168.69±6.13 K, including some allowance for small latitudinal, longitudinal, and temporal variations. That allows for the possibility of a wider temperature range of 163-175 K at the 1-bar level than the commonly assumed value of 166 K from the Galileo probe. The profile itself provides an alternative a priori profile for retrieval of temperatures from remote sensing of thermal emission. Temperature at the 1-bar level is a particularly important reference since it serves as an “anchor” in models for retrieving the atmospheric composition and thus has a potential effect on the derived water abundance. It also broadens the range of acceptable upper boundary temperatures for interior models. The corrected data will also serve as a baseline for the radio occultation of Jupiter observations planned in Juno’s extended mission.

How to cite: Gupta, P., Atreya, S. K., Steffes, P. G., Allison, M. D., Bolton, S. J., Fletcher, L. N., Guillot, T., Helled, R., Levin, S., Li, C., Lunine, J. I., Miguel, Y., Orton, G. S., Waite, J. H., and Withers, P.: Jupiter’s Temperature Structure: A Reassessment of the Voyager Radio Occultation Results, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-966, https://doi.org/10.5194/egusphere-egu22-966, 2022.

15:19–15:25

EGU22-2448

ECS

On-site presentation

The number and location of Jupiter's circumpolar cyclones explained by vorticity dynamics

Nimrod Gavriel and Yohai Kaspi

The Juno mission observed that both poles of Jupiter have polar cyclones that are surrounded by a ring of circumpolar cyclones (CPCs). The north pole holds eight CPCs and the south pole possesses five, with both circumpolar rings positioned along latitude ~84° N/S. Here we explain the location, stability and number of the Jovian CPCs by establishing the primary forces that act on them, which develop because of vorticity gradients in the background of a cyclone. In the meridional direction, the background vorticity varies owing to the planetary sphericity and the presence of the polar cyclone. In the zonal direction, the vorticity varies by the presence of adjacent cyclones in the ring. Our analysis successfully predicts the latitude and number of circumpolar cyclones for both poles, according to the size and spin of the respective polar cyclone. Moreover, the analysis successfully predicts that Jupiter can hold circumpolar cyclones, whereas Saturn currently cannot. Finally, this force balance explains the oscillation patterns observed in the south polar cyclones over a period of 4 years since Juno’s arrival to Jupiter. The match between the theory and observations implies that vortices in the polar regions of the giant planets are largely governed by barotropic dynamics, and that the movement of other vortices at high latitudes is also driven by interaction with the background vorticity.

How to cite: Gavriel, N. and Kaspi, Y.: The number and location of Jupiter's circumpolar cyclones explained by vorticity dynamics, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2448, https://doi.org/10.5194/egusphere-egu22-2448, 2022.

15:25–15:31

EGU22-3143

Presentation form not yet defined

Characteristics of Hazes in the Atmosphere of Jupiter from JunoCam Observations

Glenn Orton, Thomas Momary, John Rogers, Gerald Eichstaedt, Candice Hansen, Caleb Keaveney, Kevin Kelly, Daniel Wen, and Shawn Brueshaber

A complex series of high-altitude clouds and hazes have been unveiled by images from the Juno mission’s JunoCam instrument. They appear to be ubiquitous at higher latitudes in both of Jupiter’s hemispheres but are particularly pronounced in the north. Juno’s polar orbit and JunoCam’s filter centered on the 889-nm absorption band of methane make JunoCam uniquely suited to observing high-altitude polar features. Among these are the North and South Polar Hoods, which JunoCam’s methane-band filter reveals in greater detail than from the Earth, together with bright and dark haze bands. These bright and dark bands commonly appear together in bundles, indicating vertical structure in widespread haze layers. Some bright hazes near the terminator exhibit an apparent color dispersion, appearing bluish on the side generally in the direction of illumination and reddish on the other, an effect that is consistent with more efficient scattering by shorter-wavelength light. The morphology of the observed haze bands appears to be quite different from the well-known zonal wind profile affecting the main cloud deck. On the other hand, some, including a semi-persistent long band of haze near the South Pole, are related to the locations of underlying cyclones and chaotic cyclonic features known as folded filamentary regions. Our high-resolution observations of Jupiter’s limb have revealed hazes, some continuous with the lower atmosphere and others that are singly and doubly detached. Toward high northern latitudes, these limb hazes become completely opaque.

How to cite: Orton, G., Momary, T., Rogers, J., Eichstaedt, G., Hansen, C., Keaveney, C., Kelly, K., Wen, D., and Brueshaber, S.: Characteristics of Hazes in the Atmosphere of Jupiter from JunoCam Observations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3143, https://doi.org/10.5194/egusphere-egu22-3143, 2022.

15:31–15:37

EGU22-5454

ECS

Virtual presentation

Temporal variations in spectral reflectivity and vertical cloud structure of Jupiter’s Great Red Spot and its surroundings

Asier Anguiano-Arteaga, Santiago Pérez-Hoyos, Agustín Sánchez-Lavega, and Patrick Irwin

Jupiter's Great Red Spot (GRS) is a remarkable phenomenon among solar system atmospheres. In addition to its unique dynamical properties, the vertical structure of its clouds and hazes is a relevant subject of study, being of particular interest the unknown chromophore species responsible for the GRS characteristic reddish color. In a recently published paper (Anguiano-Arteaga et al., 2021) we showed the existence of a stratospheric haze (P < 100 mbar) that seemed to be compatible with the chromophore-candidate proposed by Carlson et al. (2016), although a second coloring agent located in the upper tropospheric levels (P < 500 mbar) was also suggested.

In this study, we have analyzed high-resolution images obtained with the Hubble Space Telescope’s Wide Field Camera 3 between 2015 and 2021, with a spectral coverage from the UV to the near IR, including two methane absorption bands. Following the same procedure as in our previous paper, we have obtained the spectral reflectivity of the GRS and a few dynamically interesting regions in the surrounding area under different viewing geometries.

From the measured spectra, and following the scheme proposed by Anguiano-Arteaga et al. (2021), we retrieved several key atmospheric parameters (optical depths, particle vertical and size distributions and refractive indices) for each of the regions using the NEMESIS radiative transfer suite (Irwin et al., 2008). We show the spatial and temporal variations on these parameters, including the evolution of the properties of the chromophore species.

References

- Anguiano-Arteaga, A., Pérez-Hoyos, S., Sánchez-Lavega, A., Sanz-Requena, J. F., & Irwin, P. G. J. (2021). Vertical distribution of aerosols and hazes over Jupiter's Great Red Spot and its surroundings in 2016 from HST/WFC3 imaging. J. Geophys. Res. Planets., 126, e2021JE006996 https://doi.org/10.1029/2021JE006996

- Carlson, R.W., Baines, K.H., Anderson, M.S., Filacchione, G., & Simon, A.A. (2016). Chromophores from photolyzed ammonia reacting with acetylene: Application to Jupiter’s Great Red Spot. Icarus, 274, 106-115. https://doi.org/10.1016/j.icarus.2016.03.008

- Irwin, P.G.J., Teanby, N.A., de Kok, R., Fletcher, L.N., Howett, C.J.A., Tsang, C.C.C., Wilson, C.F., Calcutt, S.B., Nixon, C.A., & Parrish, P. D. (2008). The NEMESIS planetary atmosphere radiative transfer and retrieval tool. J. of Quant. Spec. and Radiative Transfer, 109 , 1136-1150. https://doi.org/10.1016/j.jqsrt.2007.11.006

How to cite: Anguiano-Arteaga, A., Pérez-Hoyos, S., Sánchez-Lavega, A., and Irwin, P.: Temporal variations in spectral reflectivity and vertical cloud structure of Jupiter’s Great Red Spot and its surroundings, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5454, https://doi.org/10.5194/egusphere-egu22-5454, 2022.

Discussion

15:37–15:43

EGU22-8122

On-site presentation

A Genetic Algorithm Approach to Infer Jupiter's Rossby Wave Structure from JunoCam Images

Gerald Eichstädt, Glenn Orton, and Candice Hansen-Koharcheck

We use a selected pair of JunoCam images taken during the inbound or outbound branch of some of Juno's perijoves to derive a polar azimuthal vorticity map. Our goal is the inference of a Rossby wave structure from such vorticity map; Rossby waves are observed in one or more jets in Jupiter's south polar region (Rogers et al., 2022, Icarus 372, 114742). We implement a genetic algorithm to approach this goal. A genetic algorithm is a computer model inspired by Darwinian evolution.

We describe the phenotypical aspect of a Rossby wave structure by means of meridionally Gauss-weighted Fourier terms. The sum of those terms distort circles of latitudes meridionally into more general fibers. The standard deviation of the vorticity values along such a fiber provides a measure of the fitness of a modelled Rossby wave structure with respect to the observed vorticity map.

The genotypical aspect encodes each meridionally Gauss-weighted Fourier term by a gene. Such a gene encodes each parameter of the term by an integer number, which itself is encoded by a string of bits. A genome consists of a set of such genes. It represents the set of terms needed to be summed up into the meridional distortions approximating the Rossby wave structure. The genome describes and represents a member of a population. Our algorithm evolves such a population of genomes. The population starts with genomes initiated with parameters set to zero or to random values, which are then evolved through rounds of mutation and recombination. The basic evolution steps are

the creation of a new genome by recombining two randomly selected genomes of the population,
mutation of the new genome,
the calculation of the fitness of the new genome, and
the survival of the fittest genomes.

Recombination of two genomes selects randomly about half the genes from each of the two genomes to be recombined. Single bits of the parameters of the genome flip with a low probability to introduce random point mutations. New genes can form that way. Genes are deleted with a low probability after recombination in order to keep the genomes and hence the approximation of the Rossby structure simple.

Several populations can be run with different pseudo-random number seeds in order to investigate the reproducibility of the results.

The development of the algorithm is motivated by our intention to observe changes of the Rossby wave structure over time on the basis of JunoCam images, but also to define reasonable global initial conditions for simulation runs of the polar regions.

How to cite: Eichstädt, G., Orton, G., and Hansen-Koharcheck, C.: A Genetic Algorithm Approach to Infer Jupiter's Rossby Wave Structure from JunoCam Images, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8122, https://doi.org/10.5194/egusphere-egu22-8122, 2022.

15:43–15:49

EGU22-9155

ECS

Virtual presentation

Evidence for Multiple Ferrel-Like Cells on Jupiter

Keren Duer, Nimrod Gavriel, Eli Galanti, Yohai Kaspi, Leigh Fletcher, Tristan Guillot, Scott Bolton, Steven Levin, Sushil Atreya, Davide Grassi, Andrew Ingersoll, Cheng Li, Liming Li, Jonathan Lunine, Glenn Orton, Fabiano Oyafuso, and Hunter Waite

Jupiter’s atmosphere is governed by multiple jet streams, which are strongly tied to its three-dimensional atmospheric circulation. Lacking a solid surface, several theories exist for how the meridional circulation extends into the interior. Here we show, collecting evidence from multiple instruments of the Juno mission, the existence of mid-latitudinal, turbulent driven, meridional circulation cells, similar to the Ferrel cells on Earth. Different than Earth, which contains only one such cell in each hemisphere, Jupiter can incorporate multiple cells due to its large size and fast spin. The cells form regions of upwelling and downwelling, which we show are clearly evident in Juno’s MWR data between latitudes 60S and 60N. The existence of these cells is confirmed by reproducing the ammonia observations using an advection-relaxation model. This study solves a long-standing puzzle regarding the nature of Jupiter’s sub-cloud dynamics and provides evidence for 8 cells in each Jovian hemisphere.

How to cite: Duer, K., Gavriel, N., Galanti, E., Kaspi, Y., Fletcher, L., Guillot, T., Bolton, S., Levin, S., Atreya, S., Grassi, D., Ingersoll, A., Li, C., Li, L., Lunine, J., Orton, G., Oyafuso, F., and Waite, H.: Evidence for Multiple Ferrel-Like Cells on Jupiter, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9155, https://doi.org/10.5194/egusphere-egu22-9155, 2022.

15:49–15:55

EGU22-9566

On-site presentation

Jupiter’s Elevated Atmosphere as Illuminated by the Galilean Satellites

Mathias Benn, John L. Jørgensen, Peter S. Jørgensen, Troelz Denver, Matija Herceg, and John E. Connerney

15:55–16:01

EGU22-10499

ECS

Highlight

Presentation form not yet defined

Multi-Instrument Observations of a Jovian Thunderstorm from Juno and Ground-Based Telescopes

Shawn Brueshaber

Multi-Instrument Observations of a Jovian Thunderstorm from Juno and Ground-Based Telescopes

Brueshaber¹, G. Orton¹, S. Brown¹, S. Levin¹, A. Ingersoll², C. Hansen³, D. Grassi⁴, A. Mura⁴, L. N. Fletcher⁵, S. Bolton⁶

On November 29^th, 2021, the Juno Spacecraft completed its 38^th perijove as part of its Extended Mission. Three of the spacecraft’s instruments, JunoCam, JIRAM, and MWR, imaged a thunderstorm in the NEB at approximately 9^oN planetocentric latitude. JunoCam and the MWR captured data from an altitude of a few thousand kilometers, following JIRAM’s images of the storm four hours before. Ground-based observers tracked this storm over a period of a few days, providing a planetary-scale perspective to Juno’s observations.

The morphology of the storm as shown in JunoCam’s RGB filters (observations with the methane filter were not conducted), and from ground-based observers, is highly suggestive of a moist-convective thunderstorm complex with clouds reaching the upper troposphere. Furthermore, JunoCam images suggest that the storm is shaped by vertical shear as the presumed anvil is offset from a thicker region of white clouds. On Earth, vertical shear is necessary for non-tropical cyclone thunderstorm systems to persist for prolonged periods. JunoCam imaging also suggests a previous anvil top located to the west of the optically thick clouds, which may indicate a temporarily-varying nature to the convection, which is consistent with ground-based observations showing upwelling at this location for several days before the Juno images. JIRAM’s observations show a cold spot at 4.78 µm near the region of the thickest white clouds, which would be expected from optically thick clouds blocking heat transport to space. Spectroscopic retrievals show a slight enhancement of H₂0 and PH₃ compared to the surrounding region, which is expected from upwelling from the interior. The MWR instrument detected numerous lightning flashes at 0.6 GHz (Channel 1) and several flashes at 1.2 and 2.4 GHz (Channels 2 and 3, respectively), which are correlated with JunoCam and JIRAM’s observations of optically thick clouds.

Given the close approach of the Juno spacecraft with three instruments observing the storm, this feature may be the most highly instrumented observation of a Jovian thunderstorm to date. The cloud morphology, size, optical thickness of its clouds, and lightning detection in this feature suggest that the storm is probably the equivalent of a terrestrial mesoscale convective complex, possibly composed of multiple individual thunderstorms as is the case on Earth. However, differences between jovian and terrestrial thunderstorms exist, most notably the lack of a surface to help focus convection and the composition of the atmosphere. Nevertheless, the observations that we detail here may ultimately shed light on the mechanisms that form, sustain, and characterize moist convective storms in hydrogen-dominated atmospheres. Here we summarize our observations to date and perform a preliminary comparison to terrestrial and Saturnian thunderstorms.

¹ Jet Propulsion Laboratory and California Institute of Technology

²California Institute of Technology

³ Planetary Science Institute

⁴ Institute for Space Astrophysics and Planetology INAF-IAPS

⁵ School of Physics and Astronomy, University of Leicester

⁶ Southwest Research Institute

How to cite: Brueshaber, S.: Multi-Instrument Observations of a Jovian Thunderstorm from Juno and Ground-Based Telescopes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10499, https://doi.org/10.5194/egusphere-egu22-10499, 2022.

16:01–16:07

EGU22-10779

Virtual presentation

Limb darkening values of Jupiter’s atmosphere at 600 MHz measured by Juno Microwave Radiometer

Cheng Li, Ananyo Bhattacharya, Sushil Atreya, Steven Levin, Scott Bolton, Tristan Guillot, Pranika Gupta, Andrew Ingersoll, Jonathan Lunine, Glenn Orton, Paul Steffes, Hunter Waite, and Michael Wong

Sensing potential microwave opacity sources well below the water cloud potentially allows us to probe whether rock-forming species are present in Jupiter—here, specifically, the alkali metals. The measurement of limb darkening (relative change of the brightness temperature from nadir viewing to limb viewing at the 45-degree emission angle) by the Juno Microwave Radiometer (MWR) is very precise ( 0.1%) due to the stability of the instrument. We analyzed the MWR data from perijove 1 to perijove 12 and found that the 600 MHz channel of the MWR observed a consistent limb darkening value of around 14% from 40^oS to 40^oN for Jupiter’s atmosphere while thermodynamic models predict that the limb darkening should be about 18%. The 4% difference is well above the uncertainty of the measurement. We construct end-member models to investigate the possible cause. We have examined the effect of 1) ammonia depletion, 2) the existence of a deep radiative layer between 1000 ~ 2000 K, 3) concentration of alkali metals, 4) opacity models of water vapor continuum and 5) opacity models of ammonia and concluded that the most likely cause is the presence of alkali metals, which thermally dissociate at temperatures > 1000 K. Other factors may also contribute to the anomalous limb darkening. To fully resolve the degeneracy, laboratory measurements of the opacities of ammonia and water at high temperatures are recommended.

How to cite: Li, C., Bhattacharya, A., Atreya, S., Levin, S., Bolton, S., Guillot, T., Gupta, P., Ingersoll, A., Lunine, J., Orton, G., Steffes, P., Waite, H., and Wong, M.: Limb darkening values of Jupiter’s atmosphere at 600 MHz measured by Juno Microwave Radiometer, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10779, https://doi.org/10.5194/egusphere-egu22-10779, 2022.

16:07–16:13

EGU22-11527

ECS

On-site presentation

The first direct measurement of the saturnian stratospheric winds

Bilal Benmahi, Thibault Cavalié, Thierry Fouchet, Emmanuel Lellouch, Raphael Moreno, Sandrine Guerlet, Aymeric Spiga, and Deborah Bardet

Numerous past observations of Saturn by ground based and space telescopes have monitored the movements of clouds and derived direct measurements of tropospheric wind speeds, giving insights into the tropospheric circulation of the planet. The most remarkable feature is a broad and fast equatorial prograde jet, reaching 400-450 m/s. Saturn's stratospheric dynamics is less well known. At low latitudes, it is characterized by the thermal signature of an equatorial oscillation: the observed thermal structure implies that there is a strong oscillating vertical shear of the zonal winds throughout the stratosphere, however, wind speeds in this region cannot be measured by cloud-tracking techniques and remain unknown.

The objective of our study is to measure the stratospheric zonal winds of Saturn and unveil the circulation of this layer by observing it in the submillimeter range with the ALMA interferometer. For this, we observed the spectral lines of HCN at 354 GHz and CO at 345 GHz emitted from the limb of the planet. The pressure level at which we measure the winds is about 0.2 mbar. Thanks to the high spatial and spectral resolution of ALMA observations at 345 GHz, we measured the central frequencies of the emission lines in the whole limb, subtracted the rigid rotation of the planet, and thus derived the Doppler shift due to the atmospheric motions of the probed layer, i.e. the stratospheric winds. The method we used in this study was first developed to observe the stratospheric winds in Jupiter (Cavalié et al. 2021).

Saturn's rings have limited our wind observations to latitudes north of 20°S. The zonal winds obtained in the eastern and western limbs are consistent within error bars. We most noticeably detected a very broad eastward jet that spreads from 20°S to 20°N with an average speed of exceeding 250 m/s.

How to cite: Benmahi, B., Cavalié, T., Fouchet, T., Lellouch, E., Moreno, R., Guerlet, S., Spiga, A., and Bardet, D.: The first direct measurement of the saturnian stratospheric winds, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11527, https://doi.org/10.5194/egusphere-egu22-11527, 2022.

Plasma and Magnetosphere

16:13–16:19

EGU22-350

ECS

Virtual presentation

Investigation of the features of heavy ion acceleration events in the Jovian magnetotail using Juno/JEDI data

Georgia Moutsiana, George Clark, Matina Gkioulidou, Ioannis Daglis, and Barry Mauk

16:19–16:25

EGU22-6455

On-site presentation

JIRAM observations of Jupiter's upper troposphere

Davide Grassi, Alessandro Mura, Giuseppe Sindoni, Alberto Adriani, Sushil Atreya, Gianrico Filacchione, Leigh Fletcher, Jonathan Lunine, Maria Luisa Moriconi, Glenn Orton, Christina Plainaki, Federico Tosi, Angelo Olivieri, Gerald Eichstaedt, Candice Hansen, Bianca Maria Dinelli, Alessandra Migliorini, Giuseppe Piccioni, and Scott Bolton

16:25–16:31

EGU22-6537

Presentation form not yet defined

Jovian Synchrotron Observations From The Juno Microwave Radiometer

Steve Levin, Virgil Adumitroaie, Daniel Santos-Costa, and Scott Bolton and the Juno Microwave Radiometer Team

The Juno Microwave Radiometer (MWR) is in a unique position to measure the synchrotron emission from Jupiter’s inner radiation belts. Juno is a spinning spacecraft in a highly eccentric polar orbit about Jupiter, with perijoves at about 5000 km above the cloudtops. From this unique vantage point, the Juno Microwave Radiometer (MWR) has measured the radio emission in 6 channels, at wavelengths ranging from approximately 1.4 to 50 cm, with 100 ms sampling throughout each spin of the spacecraft, since the first science pass in August of 2016. Synchrotron emission is emitted in a narrow cone about the electron’s direction of motion, so Earth-based observations are limited by our equatorial vantage point. The Juno data set provides a remarkable view of the Jovian synchrotron emission over a wide range of viewing angles, from inside the radiation belts. While the MWR synchrotron data set is unprecedented, the size and variety of the data set also make analysis complex. We have therefore begun by extracting a limited subset of the data. For each channel during each perijove pass, we have determined the peak emission observed in the equatorial lobe and in the high-latitude lobes. Using these data, we determine the spectral index of the synchrotron emission as a function of frequency, from 0.6 GHz to 22 GHz. Results will be compared with models to examine the energy distribution of electrons.

How to cite: Levin, S., Adumitroaie, V., Santos-Costa, D., and Bolton, S. and the Juno Microwave Radiometer Team: Jovian Synchrotron Observations From The Juno Microwave Radiometer, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6537, https://doi.org/10.5194/egusphere-egu22-6537, 2022.

16:31–16:37

EGU22-8268

Presentation form not yet defined

Magnetosphere-Ionosphere-Thermosphere Coupling study at Jupiter Based on Juno First 30 Orbits and Modelling Tools

Michel Blanc, Sariah Al Saati, Noe Clement, Yuxian Wang, Corentin Louis, Nicolas Andre, Laurent Lamy, Jean-Claude Gérard, Bertrand Bonfond, George Clark, Barry Mauk, Frederick Allegrini, Randy Gladstone, Scott Bolton, Stavros Kotsiaros, and William Kurth

The dynamics of the Jovian magnetosphere is controlled by the complex interplay of the planet’s fast rotation, its solar-wind interaction and its main plasma source at the Io torus, mediated by coupling processes involving its thermosphere, ionosphere and magnetosphere, referred to as “MIT coupling processes”. At the ionospheric level, these processes can be characterized by a set of key parameters which include ionospheric conductances, currents and electric fields, transport of charged particles along field lines which carry electric currents connecting the ionosphere and magnetosphere, and among them fluxes of electrons precipitating into the upper atmosphere which trigger auroral emissions. Determination of these key parameters in turn makes it possible to estimate the net deposition/extraction of momentum and energy into/out of the Jovian upper atmosphere. A method based on a combined use of Juno multi-instrument data (MAG, JADE, JEDI, UVS, JIRAM and WAVES) and three modelling tools was first developed by Wang et al. (2021) and applied to an analysis of the first nine Juno orbits to retrieve these key parameters along the Juno magnetic footprint. In this communication we will extend this method to the first thirty Juno science orbits and to both north and south main auroral ovals crossings. Our results make it possible to characterize how the local systems of field-aligned electric currents, height-integrated ionospheric conductances, electric currents and fields, and Joule and particle heating rates vary across the main ovals between their poleward and equatorward edges. They suggest that southern current systems display a trend consistent with the generation of a region of sub-corotating ionospheric plasma poleward of the main aurora, while this dominant trend is not found around the northern main auroral oval.

How to cite: Blanc, M., Al Saati, S., Clement, N., Wang, Y., Louis, C., Andre, N., Lamy, L., Gérard, J.-C., Bonfond, B., Clark, G., Mauk, B., Allegrini, F., Gladstone, R., Bolton, S., Kotsiaros, S., and Kurth, W.: Magnetosphere-Ionosphere-Thermosphere Coupling study at Jupiter Based on Juno First 30 Orbits and Modelling Tools, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8268, https://doi.org/10.5194/egusphere-egu22-8268, 2022.

Coffee break

Chairpersons: Yamila Miguel, Paul Hartogh

17:00–17:05

Discussion/Transition

17:05–17:11

EGU22-8761

ECS

On-site presentation

Plasmoids in the Jovian Magnetotail: Statistical Survey of Ion Acceleration with Juno Observations

Aljona Blöcker, Elena Kronberg, Elena Grigorenko, George Clark, Marissa Vogt, and Elias Roussos

Jupiter's magnetosphere provides a unique natural laboratory to study processes of energy transport and transformation. Spatially confined structures such as plasmoids generate strong electric fields in the Jovian magnetotail and are responsible for ion acceleration to high energies. We focus on the effectiveness of ion energization and acceleration in plasmoids. Therefore, we present a statistical study of plasmoid structures in the predawn magnetotail, which were identified in the magnetometer data of the Juno spacecraft from 2016 to 2018 and documented by Vogt et al. (2020). For our study we additionally use the energetic particle observations from the Jupiter Energetic Particle Detector Instrument (JEDI) which discriminates between different ion species. We are particularly interested in the analysis of the acceleration and energization of oxygen, sulfur, helium and hydrogen ions in plasmoids and how these processes are affected by the event properties, such as the radial distance and the local time of the observed plasmoids inside the magnetotail, and the electromagnetic turbulence. We find significant heavy ion energization in plasmoids close to the current sheet center which is in line with the previous statistical results on acceleration in plasmoids based on Galileo observations conducted by Kronberg et al. (2019). The observed effectiveness of the energization is dependent on the position of Juno during the plasmoid event. Our results show no dependence between electromagnetic turbulence and non-adiabatic acceleration for heavy ions during plasmoids which is in opposition to the findings of Kronberg et al. (2019).

How to cite: Blöcker, A., Kronberg, E., Grigorenko, E., Clark, G., Vogt, M., and Roussos, E.: Plasmoids in the Jovian Magnetotail: Statistical Survey of Ion Acceleration with Juno Observations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8761, https://doi.org/10.5194/egusphere-egu22-8761, 2022.

17:11–17:17

EGU22-9391

On-site presentation

Magnetosphere-ionosphere coupling at Jupiter during Juno’s Prime mission

Gabrielle Provan, Aneesah Kamran, Emma Bunce, Stan Cowley, and Jon Nichols

We study magnetosphere-ionosphere coupling at Jupiter during the Juno prime mission, considering magnetic field observations from Juno’s Perijoves 1-32. We compare the azimuthal magnetic field and the associated determination of Jupiter’s ionospheric meridional Pedersen current, with predictions from a model of magnetosphere-ionosphere coupling developed at the University of Leicester. We find that the Leicester model closely predicts the magnitude of the residual azimuthal field component of the field across the middle and outer magnetosphere regions, and across the tail. However, we highlight two areas of discrepancies between the model and the data. On field lines mapping to the outer magnetosphere region, the model predicts an increase in the magnitude of the Bphi component of the magnetic field with ionospheric colatitude, whilst we observe a decrease. This could suggest that the community needs an updated ionospheric angular velocity flow model for the Juno era. Furthermore, we do not observe the predicted upward-directed current at the boundary between the outer magnetosphere and field lines mapping to the tail. Currently the model includes a constant ionospheric conductivity. We suggest that the model might be improved by considering a variable ionospheric conductivity. Finally, we produce maps of meridional ionospheric currents and discuss the variation of ionospheric currents with local time.

How to cite: Provan, G., Kamran, A., Bunce, E., Cowley, S., and Nichols, J.: Magnetosphere-ionosphere coupling at Jupiter during Juno’s Prime mission, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9391, https://doi.org/10.5194/egusphere-egu22-9391, 2022.

17:17–17:23

EGU22-10177

ECS

Presentation form not yet defined

A Comparative Analysis of Jupiter’s Northern Aurora using Juno’s MWR, UVS, and JIRAM Instruments

Amoree Hodges, Paul Steffes, Thomas Greathouse, Alessandro Mura, Randy Gladstone, Hunter Waite, Fabiano Oyafuso, Shannon Brown, Steven Levin, and Scott Bolton

This study continues the work from Hodges et al. (2020) to further analyze microwave emissions associated with Jupiter’s aurorae as seen by the 600 MHz channel of the MicroWave Radiometer (MWR) onboard the Juno spacecraft. The MWR can obtain spatial maps of the northern aurora. These maps allow a two-dimensional comparison of auroral observations at microwave, ultraviolet, and infrared frequencies. Each spectral region provides information on different particles of the auroral plasma. For example, microwave observations provide information on the electron density content and structure. Ultraviolet observations provide insight on the content and morphology of the Lyman series of H and the Lyman, Werner, and Rydberg bands of H₂. Lastly, infrared observations provide information on the content and structure of H₃⁺ ions.

The UltraViolet Spectrograph (UVS) and the Jovian Infrared Auroral Mapper (JIRAM) have higher resolution observations than the MWR (Gladstone et al. 2014; Adriani et al. 2014; Janssen et al. 2017). To compare observations from these three instruments, the UVS and JIRAM observations are convolved with the antenna beam-pattern of the 5x5 patch antenna array for the 600 MHz channel with a half-power beamwidth 20° (Janssen et al. 2017). The convolution allows UVS and JIRAM data to smear and provide a resolution similar to MWR observations. This process facilitates the comparative analysis of microwave, ultraviolet, and infrared observations of Jupiter’s northern aurora. This work reports on the results of the convolved UVS and JIRAM maps compared to MWR observations from previous perijoves.

How to cite: Hodges, A., Steffes, P., Greathouse, T., Mura, A., Gladstone, R., Waite, H., Oyafuso, F., Brown, S., Levin, S., and Bolton, S.: A Comparative Analysis of Jupiter’s Northern Aurora using Juno’s MWR, UVS, and JIRAM Instruments, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10177, https://doi.org/10.5194/egusphere-egu22-10177, 2022.

17:23–17:29

EGU22-10740

Presentation form not yet defined

Multi-zonal parametric model of the Jovian synchrotron radiation belt updated from the Juno mission observations

Virgil Adumitroaie, Steven Levin, Fabiano Oyafuso, Daniel Santos-Costa, and Scott Bolton

In Jupiter’s vicinity, Juno’s remote-sensing experiment, the Microwave Radiometer (MWR), captures thermal and non-thermal emissions from the atmosphere and magnetosphere. Furthermore, other scientific instruments on the spacecraft register the signatures of space charged particles and the planet’s magnetic field. The separation of contributions from several existing emission sources (cosmic microwave background, galactic emission, planetary thermal emission and synchrotron radiation belts) is a necessary step in the retrieval of atmospheric composition values from MWR’s low-frequency radiative observations.

The ad hoc multi-parameter, multi-zonal model of Levin et al. (2001) for synchrotron emission has been updated based on a subset of the MWR in-situ data. This model employs an empirical electron-energy distribution, which originally has been adjusted exclusively from Very Large Array (VLA) observations made prior to the Juno mission. The approaches considered and challenges confronted are discussed here. The model will be updated frequently as additional observations from the MWR and magnetometer instruments are taken into account.

How to cite: Adumitroaie, V., Levin, S., Oyafuso, F., Santos-Costa, D., and Bolton, S.: Multi-zonal parametric model of the Jovian synchrotron radiation belt updated from the Juno mission observations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10740, https://doi.org/10.5194/egusphere-egu22-10740, 2022.

Magnetic Field, Deep Atmosphere and Interior

17:29–17:35

EGU22-2981

ECS

On-site presentation

Jupiter's internal structure and dynamics inferred from a high resolution magnetic field and secular variation model

Shivangi Sharan, Benoit Langlais, Hagay Amit, Mathis Pinceloup, Erwan Thébault, and Olivier Verhoeven

The interior of Jupiter can be described broadly as a dense core surrounded by fluids, dominantly hydrogen and helium. The hydrogen rich metallic fluid generates the strongest planetary magnetic field in the Solar System. Modelling and interpreting this field give essential information about the dynamo process inside Jupiter. However, the depth of the dynamo region and the temporal variation of the magnetic field are still debatable. Here we use the Juno mission data across four years to derive an internal magnetic field model using spherical harmonic functions. We take the fluxgate magnetometer measurements acquired during the first 28 perijoves to compute a main field model to degree 13, and a secular variation model to degree 8. The power spectrum of the main field model is used to investigate the radius of the dynamo region. We use the properties of the non-zonal and quadrupole family spectra to infer that the convective region has an upper boundary at 0.843 ± 0.015 Jupiter radius. The slope of the secular variation timescales indicate that the dynamo is dominated by advective effects. The secular variation (SV) displays a maximum near the equator with a dipole structure in agreement with zonal drift of the Great Blue Spot. However, numerous small scale SV structures at mid and high latitudes suggest that the flow at the interior is complex involving both zonal and non-zonal features.

How to cite: Sharan, S., Langlais, B., Amit, H., Pinceloup, M., Thébault, E., and Verhoeven, O.: Jupiter's internal structure and dynamics inferred from a high resolution magnetic field and secular variation model, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2981, https://doi.org/10.5194/egusphere-egu22-2981, 2022.

17:35–17:41

EGU22-8999

Presentation form not yet defined

Juno Probes the Dynamo Region and Detects Secular Variation of the Magnetic Field

Jack Connerney

A spherical harmonic model of the magnetic field of Jupiter is obtained from vector magneticfield observations acquired by the Juno spacecraft during 32 of its first 33 polar orbits. These Prime Mission orbits sample Jupiter's magnetic field nearly uniformly in longitude (~11° separation) as measured at equator crossing. The planetary magnetic field is represented with a degree 30 spherical harmonic and the external field is approximated near the origin with a simple external spherical harmonic of degree 1. Partial solution of the underdetermined inverse problem using generalized inverse techniques yields a model (“JRM33”) of the planetary magnetic field with spherical harmonic coefficients reasonably well determined through degree and order 13. Useful information regarding the field extends through degree 18, well fit by a Lowes' spectrum with a dynamo core radius of 0.807 +/- 0.006 Rj, presumably the outer radius of the convective metallic hydrogen region that exists beneath a layer stably stratified by precipitation of “helium rain”. This new model provides a most detailed view of a planetary dynamo and evidence of advection of the magnetic field by deep zonal winds in the vicinity of the Great Blue Spot (GBS), an isolated and intense patch of flux near Jupiter's equator. Comparison of the JRM33 and JRM09 models suggests secular variation of the field in the vicinity of the GBS during Juno's nearly 5 years of operation in orbit about Jupiter. The observed secular variation is consistent with the penetration of zonal winds to a depth of ~3,500 km where a flow velocity of ~0.04 ms−1 is required to match the observations. At this rate the GBS circles the planet in about 350 years.

How to cite: Connerney, J.: Juno Probes the Dynamo Region and Detects Secular Variation of the Magnetic Field, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8999, https://doi.org/10.5194/egusphere-egu22-8999, 2022.

17:41–17:47

EGU22-9551

On-site presentation

Continuation and Damping of Zonal Flows by Stably Stratified layers

Wieland Dietrich, Paula Wulff, and Ulrich R. Christensen

Geostrophic zonal flows appear naturally in rapidly rotating, convective systems that resemble the convective atmospheres of giant planets. However, the depth of the flows is potentially limited by stratified layers inhibiting convection. Here we study the continuation and damping of zonal flows across the interface and into such a stratified layer. In order to analyse the problem in a systematic way, we validate cartesian and analytical models by using spherical shell models with enforced axisymmetry. Compared to full 3D models they provide the advantage of being much less computationally demanding and producing plentiful jets within the shell's tangent cylinder.

The analytical model predicts that for weaker stratification, the damping of the jets in the stable layer follows the prediction of the classic linear theory of penetrative convection and thus scales with the length scale of the jets and the relative stratification ($N/\Omega$, where $N$ is the Brunt-V\"{a}is\"{a}l\"{a} frequency and $\Omega$ the rotation rate). However, for strong stratifications, characteristic for compositional gradients (eg. He-rain), the damping rate becomes independent of $N/\Omega$ and is solely controlled by the jet width. The axisymmetric spherical shell simulations verify this prediction over a wide range of parameters. These results yield also important consequences for modelling the wind-induced gravity field anomalies of Gas Giants.

How to cite: Dietrich, W., Wulff, P., and Christensen, U. R.: Continuation and Damping of Zonal Flows by Stably Stratified layers, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9551, https://doi.org/10.5194/egusphere-egu22-9551, 2022.

17:47–17:53

EGU22-9684

ECS

On-site presentation

Zonal Winds in the Gas Planets Driven by Convection above a Stably Stratified Layer

Paula Wulff, Wieland Dietrich, Ulrich Christensen, and Johannes Wicht

The analysis of the recent gravity measurements of Jupiter and Saturn reveal that the zonal winds observed on their surfaces reach several thousand kilometres deep into their atmospheres. However, it remains unclear which mechanism prevents them from penetrating deeper. Recent models suggest that a stably stratified region would yield the desired effect.
In this study we systematically explore the dynamics in a spherical shell where the lower third is stably stratified while convection in the outer region drives multiple zonal winds, similar to those observed on Jupiter or Saturn. We perform numerical simulations with the magnetohydrodynamic code MagIC and ignore magnetic effects in order to simplify the problem. Using a rigid lower boundary condition, vigorous multiple jets begin to develop at mid to high latitudes once the stable stratification is strong enough to effectively decouple the jet dynamics from the lower boundary. We find that the jet amplitude decay at the stable layer boundary is proportional to Ω/N, where Ω is the rotation rate and N the Brunt-Väisälä frequency that quantifies the degree of stable stratification.
Furthermore, the penetration depth of the jets is directly proportional to the jet width, i.e. the stable layer acts as a low-pass filter on the zonal winds. The structure of the winds also changes. In the convective region they are invariant along the axis of rotation, as expected. However, in the stable layer the location of the peaks in the zonal wind profile become more radially invariant with depth. This shift from cylindrical to a more spherical geometry in
the flow structure occurs due to meridional flows at the interface, thermal winds and the inverse buoyancy force in the stable layer.

How to cite: Wulff, P., Dietrich, W., Christensen, U., and Wicht, J.: Zonal Winds in the Gas Planets Driven by Convection above a Stably Stratified Layer, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9684, https://doi.org/10.5194/egusphere-egu22-9684, 2022.

17:53–17:59

EGU22-11226

Presentation form not yet defined

A model for the secular magnetic field variation caused by Jupiter’s zonal winds

Johannes Wicht and Ulrich R. Christensen

The secular variation of the geomagnetic field is routinely used to infer the flow on the top of Earth’s liquid iron core. Recent gravity measurements by the Juno spacecraft suggest that the zonal winds observed on Jupiter’s surface reach about 3000 km deep. The observed variation in Jupiter’s magnetic field could provide additional constrains on the structure and speed of the zonal winds at depth. However, the interpretation of the secular variation is complicated by the fact that the electrical conductivity and thus magnetic effects increase rapidly with depth while the zonal winds decay with depth. Here we use a simple numerical model to explore the possible secular variation due to Jupiter’s zonal winds. We restrict the simulations to the outer 10% in radius and imposed the Jupiter-like magnetic field as a potential field. Different profiles for the depth dependence on electrical conductivity and winds are explore. The shear of the zonal winds increases the magnetic field dissipation over time. The dissipation seeks to balance induction and thereby reduces the secular variation. As the simulation progresses, the secular variation observed at the surface represents the zonal flow at increasing depth. The induced field also tends to significantly reduce the effective field strength at the surface. Out results suggest that the zonal flow action heavily shapes and weakens Jupiter’s magnetic field. However, the zonal flow induced secular variation would only reflect the slower flows at depth and may not contribute much to the total secular variation.

How to cite: Wicht, J. and Christensen, U. R.: A model for the secular magnetic field variation caused by Jupiter’s zonal winds, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11226, https://doi.org/10.5194/egusphere-egu22-11226, 2022.

Ganymede

17:59–18:05

EGU22-5297

On-site presentation

Recent findings from Juno’s Stellar Reference Unit

Heidi Becker, Meghan Florence, Martin Brennan, Alexandre Guillaume, Candice Hansen, Michael Ravine, Scott Bolton, John Arballo, and James Alexander

18:05–18:11

EGU22-9546

On-site presentation

Energetic Electron lensing of Ganymede’s Magnetic Field observed by the Juno Spacecraft’s Advanced Stellar Compass

Matija Herceg, John Leif Jørgensen, Jose M. G. Merayo, Troelz Denver, Peter S. Jørgensen, Mathias Benn, Stavros Kotsiaros, and Jack E. P. Connerney

18:11–18:17

EGU22-10748

Highlight

Presentation form not yet defined

Sub-surface Observations of Ganymede’s Ice Shell from the Juno Microwave Radiometer

Shannon Brown, Scott Bolton, Sidharth Misra, Steve Levin, Zhimeng Zhang, Jonathan Lunine, David Stevenson, and Matthew Siegler

We report on observations of Ganymede’s ice shell from the Microwave Radiometer on the Juno Mission. On 7 June 2021, Juno flew within 1000 km of the surface. During the flyby, Juno’s Microwave Radiometer (MWR) observed Ganymede obtaining several swaths across Ganymede using Juno’s spin to partially map Ganymede’s ice shell in six channels ranging from 600 MHz to 22 GHz. The radiance at these frequencies originates from successively deeper layers of the sub-surface from the highest to lowest frequency. The MWR observations cover a latitude range from 20S to 60N and an east longitude range from -120 to 60 degrees, roughly centered on the Perrine region. The local solar time varies from around noon to mid-night over the longitude range. Ground-based interferometry at mm-cm wavelengths have helped characterize icy satellite surfaces with previous unresolved microwave and radar maps providing the basis for Ganymede models indicating surface temperature variations that correlate with surface albedo (Butler 2012). Previous observations at millimeter wavelengths probed the shallow sub-surface (~cm depths), and provided information on thermal properties such as emissivity and thermal inertia, show strong hemispheric differences in surface albedos, with large regions of warmer, darker terrain as well as cooler, ice-rich regions (de Kleer et al 2021). Previous full disk cm-wave observations have been hindered by the presence of Jupiter’s thermal and synchrotron emission. We present resolved brightness temperature maps and associated spectra of Ganymede with a spatial resolution of up to ~140 km (approximately 1/40^th of Ganymede’s diameter). The maps and spectra are sensitive to prominent localized thermal features in addition to the various types of terrain seen in visible and infrared images of Ganymede. Comparing the microwave spectra with maps of Ganymede reveal spectral differences corresponding to different types of terrain visible on Ganymede including bright and dark geological features. Juno’s wide range of wavelengths probe various depths providing information on porosity, water ice purity, thermal inertial and dielectric constants of the various ice regions as well as linear features thought to be associated with tectonic activity. Significant variation in the Juno MWR spectra with location suggest sub-surface ice properties are not uniform with location. The dark regions tend to exhibit the warmest microwave spectra and brighter regions are observed to have a lower brightness temperature (up to half the blackbody temperature). The coldest microwave feature observed by MWR is the Tros crater and the immediate surrounding region. We will highlight these variations and infer possible thermo-physical properties of the sub-surface ice based on radiative transfer modeling. These observations provide new constraints on the subsurface properties and complement future radar sounding observations from the JUICE mission.

How to cite: Brown, S., Bolton, S., Misra, S., Levin, S., Zhang, Z., Lunine, J., Stevenson, D., and Siegler, M.: Sub-surface Observations of Ganymede’s Ice Shell from the Juno Microwave Radiometer, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10748, https://doi.org/10.5194/egusphere-egu22-10748, 2022.

18:17–18:23

EGU22-12950

Highlight

Presentation form not yet defined

JEDI overview of Juno’s first close Ganymede flyby

George Clark and the Juno Team

18:23–18:30

Concluding discussion