Overview

Jovian lightning has been investigated by every spacecraft mission that visited Jupiter prior to Juno. Lightning is valued because it traces locations with active moist convection, presumably rooted in the water cloud layer. Occurrence rates of lightning are not spatially uniform, with increased activity in cyclonic belts as compared to anticyclonic zones.

The Juno spacecraft has detected lightning signals in UV (Giles et al. 2020), optical (Becker et al. 2020), and radio bandpasses (Kolmasova et al. 2018, Brown et al. 2018). We focus here on data from the Microwave Radiometer instrument (Janssen et al. 2017), which detects pulses at 600 MHz frequency (or 50 cm wavelength). Lightning is detected in the MWR dataset as pulses of anomaly high brightness temperature, spanning one (or sometimes more than one) integration period of 0.1 seconds. The actual lightning pulses are probably not temporally resolved by MWR, since Juno Waves detects dispersed pulses and whistlers implying source signal durations of 0.5 to 12 milliseconds (Imai et al. 2020, Kolmasova et al. 2023).

Stealth superstorms

In 2021, convective activity in the North Equatorial Belt (NEB) ceased, according to visible imaging. Over a period of several months, convection gradually began to recover, in form of "stealth superstorms" that took place at a single active longitude (Rogers et al. 2022, Wong et al. 2023, Brueshaber et al. 2025). Between September 2021 and December 2022, Juno passed over this active longitude and detected stealth superstorm activity (including pulses with MWR) on four occasions (perijoves 38, 39, 44, and 47). Figure 2 shows an HST map of a storm on PJ 44, with the (shifted) Juno spacecraft track and MWR boresight pointings at the time of lightning pulse detections. But the MWR beam is 21 degrees full width at half maximum, and signal can be detected at larger angles (just with greater attenuation). So we hypothesize that the source of the lightning was the stealth superstorm at 9.5 degrees N planetocentric latitude rather than the boresight locations.

Figure 2

Juno/MWR beam/gain/sensitivity

We can use lightning signals with a known source to determine the source power of the signal, rather than only the detected power for unlocated sources. Figure 4(A) shows the MWR pointing for a single lightning detection, with contours indicating the off-boresight angle. The source power noise floor for this particular detection is shown in panel B, where the source noise floor is a function of both the off-boresight angle (and thus the antenna gain), plus the range from Jupiter's atmosphere to Juno. Using similar pointing information for all of the detections, we were able to measure the lightning source power distribution for stealth superstorms on perijoves 38, 39, 44, and 47.

Figure 4

Comparing Jupiter and Earth Lightning power

To analyze the distribution of pulse power levels, we combined data from the four perijoves into the combined distribution shown as a blue curve in Fig. 12(A). For comparison, a shifted terrestrial lightning distribution from the FORTE satellite (Jacobson 2003) is shown in gold. In both cases, the distribution has a clear peak and shows that the median and mode of the power distribution falls within the detection range of MWR and FORTE. For the MWR data, we argue that the peaked distribution (resembling a log-normal distribution) is evidence that MWR detects typical Jovian lightning signals, rather than Jovian superbolts that are at least 1000 times stronger than the mode of the distribution. This follows from the superbolt definition of Holzworth et al. (2019) for terrestrial WWLLN lightning data in the 5-18 kHz frequency range, where superbolts had energies greater than 1 MJ, compared to a mean of about 1 kJ.

Figure 12

Comparing absolute source power between terrestrial and Jovian radio signals is challenging, partly because the relevant measurements are in very different bandpasses (Fig. 12(B)). Various power-law spectral energy distributions can be used to relate signals in terrestrial data at different frequencies, as shown for Oh (1969) and Weidman et al. (1981). If we use these spectra to extrapolate lightning modal power from WWLLN and FORTE to the 600-MHz frequency of MWR, we find that Jovian lightning is likely to be in the range of 1 to 100 times more powerful than terrestrial lightning.

Conclusions: key points

• Clustering breaks the power/location degeneracy to reveal the source power distribution of lightning signals
• Juno MWR measured an event rate of about 3 integrated pulses/sec at 600 MHz in four isolated storms
• The lightning power distribution peaks inside the MWR sensitivity range, favoring typical lightning activity (not superbolt outliers)

References

• Becker et al. 2020 - DOI: 10.1038/s41586-020-2532-1
• Brown et al. 2018 - DOI: 10.1038/s41586-018-0156-5
• Brueshaber et al. 2025 - DOI: 10.1016/j.icarus.2025.116465
• Giles et al. 2020 - DOI: 10.1029/2020JE006659
• Holzworth et al. 2019 - DOI: 10.1029/2019JD030975
• Imai et al. 2020 - DOI: 10.1029/2020GL088397
• Jacobson 2003 - DOI: 10.1029/2003JD003936
• Janssen et al. 2017 - DOI: 10.1007/s11214-017-0349-5
• Kolmasova et al. 2018 - DOI: 10.1038/s41550-018-0442-z
• Kolmasova et al. 2023 - DOI: 10.1038/s41467-023-38351-6
• Oh 1969 - DOI: 10.1109/TEMC.1969.303024
• Rogers et al. 2022 - DOI: 10.5194/epsc2022-17
• Weidman et al. 1981 - DOI: 10.1029/GL008i008p00931
• Wong et al. 2023 - DOI: 10.3390/rs15030702

How to cite: Wong, M. H., Oyafuso, F. A., Imai, M., Kolmašová, I., Mizumoto, S., Levin, S. M., Sankar, R., Simon, A. A., Brueshaber, S., Orton, G. S., Atreya, S. K., Li, C., and Bolton, S. J.: Radio pulse power distribution of lightning in Jupiter's 2021-2022 stealth superstorms, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-1054, https://doi.org/10.5194/epsc-dps2025-1054, 2025.

The poles of Jupiter are hidden from the view of Earth-orbiting and solar-plane satellites. In 2016, the arrival of the Juno spacecraft into a pole-to-pole orbit around Jupiter provided the first direct images of the Jovian poles, revealing a unique meteorological phenomenon. Each pole features a symmetrical arrangement of cyclones, with radii of ~5,000 km and wind speeds reaching 100 m/s. These formations comprise one polar cyclone at each pole and a surrounding ring of circumpolar cyclones, with eight cyclones in the north and five in the south. Today, more than 7 years after Juno's arrival, these two polar vortex-"crystals" have proven stable, maintaining their numbers and, on average, their latitudes and relative positions. 

The balance holding the cyclones in place is explained in the first part of this research. This balance is between a natural tendency of cyclones to propagate poleward, known as "β-drift," and a similar effect that stems from an interaction between multiple cyclones, causing a rejection between them. Evaluating these components using the observed properties of the cyclones exposes a band of equilibrium at latitude ~84°, matching their observed latitude, and accounts for the different number of cyclones between the north and south poles occupying that band. In addition, we demonstrate that this equilibrium cannot form on Saturn, which, although dynamically similar to Jupiter, only has a single polar cyclone at each pole. 

Analyzing the location of the cyclones throughout the Juno mission, 2 motion patterns become apparent. These patterns are presented and explained mechanistically in the second part of this research. The first is a coherent oscillatory motion of the cyclones around their mean positions, with an amplitude of ~400 km and periods of ~12 months. We find that perturbations from the balance responsible for the cyclones' mean positions can account for their radial accelerations leading to these circular motion patterns, as illustrated in the observations and in a toy model. The second motion pattern is a general westward drift of all cyclones, with southern cyclones drifting on average 7° per year and northern cyclones 3°. By analyzing the group of cyclones from a center-of-mass perspective and thus eliminating the mutual interactions between them, we find that their center of mass only feels the β-drift, which is expected to lead to a westward motion. This analysis, supported by measurements and modeling, accounts for the different drift rates between the poles.

Lastly, we explore the vertical structure of these polar cyclones. By analyzing the westward drift in a single-layer Shallow-Water model, we constrain the deformation radius of the cyclones to fit the observations, where we find that deeper cyclones result in a stronger β-drift. We use this estimation of the deformation radius to explore the vertical modes of Jupiter’s polar upper atmosphere by solving the eigenfunction problem between the 2D and 3D quasi-geostrophic models. This analysis explores and predicts the vertical structure of the polar cyclones and lays a framework for interpreting the forthcoming Microwave Radiometer (MWR) measurements expected for the north pole of Jupiter.

This work provides a unified perspective on the dynamics of Jupiter’s polar cyclones, revealing the physical principles that govern their stability, motion, and vertical structure. By linking observed cloud-level motions to deeper atmospheric dynamics, our findings offer a foundation for interpreting future MWR data from Juno. This research enhances our broader understanding of cyclonic behavior in giant planet atmospheres and sets the stage for further explorations of similar phenomena on other planetary bodies.

How to cite: Gavriel, N. and Kaspi, Y.: The Dynamics of Jupiter’s Polar Cyclones, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-625, https://doi.org/10.5194/epsc-dps2025-625, 2025.

Jupiter’s zonal wind system has its most intense jet centred at latitude 23.5° N where peak velocities reach 140 to 180 ms^-1. One of the most spectacular planetary-scale disturbances takes place on it, changing a bright whitish band of clouds into a dark belt, known as the North Temperate Belt (NTB), with the convective outbreaks and their effects in the belt being named the NTB Disturbance (NTBD). The disturbance begins with the rapid eruption of typically 1 to 3 “plumes”, bright clouds of convective origin that, after a rapid initial expansion, generate a turbulent wake formed by a turmoil of eddies and filaments that encircles the planet. We have studied the reported cases starting in 1970 and ending with the last two most recent NTBD eruptions in August-September 2020 and January-February 2025. Our analysis shows the existence of a cycle between plume outbreaks with a mean period of 4.64 years (range 3.84 to 4.87 years) for the 10 outbreaks observed between years 1970 and 2025. Interestingly, there was a large period of ~17 years (from the end of 1990 to early 2007) without eruptions (we call the “NTBD desert”). During this period, the NTB was a dark belt, populated with large and long-lived anticyclones. Other key properties of the plumes, such as their zonal velocity, initial meridional migration and zonal acceleration, and their spatial distribution and cadence, are also analyzed using ground-based and Hubble Space Telescope observations.

How to cite: Sanchez-Lavega, A., Rojas, J. F., Iñurrigarro, P., Mendi-Martos, A., Legarreta, J., Hueso, R., Simon, A., Wong, M., and Li, L.: The cycles and dynamical properties of convective outbreaks in Jupiter’s highest speed jet from a 55-year study , EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-361, https://doi.org/10.5194/epsc-dps2025-361, 2025.

Regardless of the differences among Earth, Jupiter and Saturn, several resembling phenomena occur in the atmospheres of these planets. One of the most striking is the oscillation in temperature and winds that occurs in their equatorial stratospheres on multi-year time-scales [1-3]. Decades of observations of Jupiter in the thermal IR, have shown that Jupiter’s Equatorial Stratosphere present an oscillation in temperatures between the North and South Equatorial Belts at pressure levels of 0.1-40 mbar. The vertical extension of this Jupiter Equatorial Stratospheric Oscillation (JESO) is not well determined, since retrieving temperatures above or below those levels becomes more difficult. Existing observations also suggest that the stratospheric oscillation might be affected by large convective outbreaks developing in the troposphere outside the equator and disrupting its stability [4]. The JESO is unrelated to seasons, with a variable period of 3.9-5.7 years, and numerical simulations indicate that gravity waves propagating from the troposphere are a key element of the stratospheric oscillations [5-6]. The oscillation in Saturn’s equatorial atmosphere, however, is likely related to seasonal effects with 15-year period [7].

The Cassini mission obtained observations of Saturn that showed the presence of a narrow equatorial jet located at the stratospheric hazes [8]. Recent observations of Jupiter, made by the James Webb Space Telescope (JWST), discovered an intense narrow equatorial jet located at the lower stratosphere (50-200 mbar) that has been suggested to be a deep counterpart of the JESO phenomena [9]. Additionally, recent studies in thermal infrared observations suggested that JESO might extend down to 300 mbar [10-11], thus linking the troposphere and stratosphere activity. This occurs precisely at the equator, a region where Coriolis forces vanish, complicating the usual relation between temperatures and winds that governs most dynamical aspects of the atmosphere in rapidly rotating planets.

Here we use observations taken by the Hubble Space Telescope (HST) between 2015 and 2024 at the strong methane absorption band at 890nm (FQ889N) to analyse potential temporal variations of the zonal winds and reflectivity at the equatorial latitudes. These images probe the elevated hazes at the upper troposphere (200-300 mbar), just below the narrow-elevated jet observed by JWST [9]. We present an analysis of the zonal winds over time, comparing these new winds in the methane band with previous results from Cassini [12] and JWST [9]. We investigate the potential variability of the equatorial jets in the upper troposphere and its possible relation to the lowest levels of the JESO. We also characterize the evolution of the equatorial hazes’ brightness over the same time period, which enables us to search for common trends and periodic activity. The results of this multi-year study will be presented with the goal to better understand the troposphere-stratosphere connection.

References: [1] Baldwin, et al., Reviews of Geophysics , 39, 179-229 (2001). [2] Leovy, C., et al. Nature 354, 380–382 (1991). [3] Fouchet, et al. Nature, 452, 200-202 (2008). [4] Antuñano, A, et al. Nat Astron 5, 71–77 (2021). [5] Cosentino, R. G., et al. (2017). Journal of Geophysical Research: Planets, 122, 2719–2744. [6] Cosentino, et al. The Planetary Science Journal. 1. 63 (2020). [7] Guerlet et al., Geophys. Res. Lett. 38, L09201 (2011). [8] García-Melendo et al.,
Geophys. Res. Lett., 37, L22204 (2010). [9] Hueso, R., et al. Nat Astron 7, 1454–1462 (2023). [10] Orton, G. S et al., Nature Astronomy, 7 , 190-197 (2023). [11] Antuñano, A., et al., Journal of Geophysical Research: Planets, 128 (12) (2023). [12] Porco, C.C., et al., 2003: Science, 299, 1541-1547, doi:10.1126/science.1079462.

How to cite: Sanchez Arregui, M., Antuñano, A., Hueso, R., and Sanchez Lavega, A.: A long-term study of Jupiter's equatorial atmosphere at the upper troposphere-lower stratosphere, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-782, https://doi.org/10.5194/epsc-dps2025-782, 2025.

The shallow layers of Jupiter’s atmosphere, the only region accessible to in-situ measurements, offer critical insights into the planet’s deeper structure. Radio occultation experiments are a powerful tool for investigating these layers, revealing detailed information about their thermal structure and composition. Beginning in July 2023, Juno’s extended mission carried out a series of radio occultations - the first since the Voyager era - to probe the neutral atmosphere of Jupiter down to approximately ±0.5 bar. By analyzing the refraction of radio signals as they pass through the atmosphere and comparing the results with ground-based observations, these experiments generate precise vertical profiles of key atmospheric parameters, particularly in the stratosphere
and upper troposphere.

Juno uses a coherent two-way radio link with multiple frequencies, requiring the application of ray-tracing techniques to model the propagation of uplink and downlink signals through the atmosphere. This approach enables the retrieval of pressure-temperature profiles, offering new insights into the thermal and dynamical structure of Jupiter’s atmosphere. Comparisons with contemporary ground-based measurements, as well as historical mid-infrared data from Voyager’s IRIS and Cassini’s CIRS instruments, highlight the value of these profiles in understanding atmospheric variability and circulation across different latitudes.

Since August 2024, Juno’s radio occultations have focused on Jupiter’s northern polar stratospheric vortex, a region (above ~65°N) known for its particularly low temperatures and distinct dynamical behavior. While the cold polar vortex has been detected in mid-infrared ground-based observations from VISIR and TEXES, Juno’s radio occultations offer the first opportunity to directly probe its thermal structure in detail. In this presentation, we share results from the first two years of Juno’s radio occultation campaign, highlighting pressure–temperature profiles across multiple latitudes and longitudes. These profiles help characterize the vertical extent, temperature gradients, and broader dynamical context of the polar vortex. In addition, we show how these thermal profiles can be used to quantify the jet velocity of the stratospheric vortex, providing new constraints on its intensity and latitudinal structure within Jupiter’s polar circulation.

How to cite: Smirnova, M., Galanti, E., Caruso, A., Fletcher, L. N., Buccino, D. R., Gomez Casajus, L., Hubbard, W. B., Orton, G. S., Parisi, M., Park, R. S., Zannoni, M., Steffes, P. G., Levin, S. M., Bolton, S. J., Tortora, P., and Kaspi, Y.: Analysis of Jupiter's Atmosphere Using Juno's Radio Occultations, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-573, https://doi.org/10.5194/epsc-dps2025-573, 2025.

The nature of the red colouration of Jupiter’s belts and some of its major anticyclones is still debated to this day. Sromovsky et al. (2017) proposed the existence of an “universal chromophore” by fitting Cassini/VIMS-V observations. Baines et al. (2019) concluded that this chromophore should be located in a thin layer above the ammonia clouds, giving rise to the so called “Crème Brûlée” model. Both of these works had as a basis the red compound that formed through the reaction of photolyzed ammonia with acetylene as obtained in the laboratory by Carlson et al. (2016).

However,  both Pérez-Hoyos et al. (2020) and Braude et al. (2020) found that a less blue and more vertically extended chromophore layer would fit better their HST/ WFC3 North Temperate Belt disturbance observations for the former and latitudinal swath from MUSE/VLT observations for the later, without fully discarding the possible existence of an “universal chromophore”. Recently, analysis of HST/WFC3 images of Jupiter’s Great Red Spot, its surroundings, and, Oval BA by Anguiano-Arteaga et al. (2021,2023) suggest the presence of two distinct colouring aerosols. The first being similar to the “universal chromophore” and the second one being a new UV-absorbing species below the main chromophore layer at tropospheric levels. This highlights the uncertainties on the vertical distribution of aerosols, their properties and their variability.

To address this uncertainty, we used new Jupiter spectra obtained with CARMENES (The Calar Alto High-Resolution search for M dwarfs with Exoearths with Near-infrared and optical Échelle Spectrographs) in 2019. This instrument consists of two separated spectrographs with spectral resolutions R = 80,000-100,000, covering the wavelength ranges of 0.52 to 0.96 μm and of 0.96 to 1.71 μm. The original purpose of these observations was to measure winds through the Doppler velocimetry method. We used a downgraded resolution version (R = 173-570) so the observations match the available spectral data for methane, as this resolution is enough for constraining aerosol properties. Due to the original nature of the observations, no calibration star was recorded. In order to achieve flux calibration, we used  2017 observations of Saturn with CARMENES. We employed Saturn’s B ring to obtain the response function of the instrument, since no other sources of calibration are available at the desired resolution or epoch.

We used the reflectivity (I/F) spectrum obtained with Cassini/VIMS (Cuzzi et al., 2009) at phase angles less than 3º. We applied the response function to the centre of disc spectrum of Saturn and compared the obtained reflectivity spectrum with results from Clark and McCord (1979) and Mendikoa, et al. (2017). Lastly, we applied the flux calibration to the Jupiter observations and compared them results from Mendikoa, et al., (2017) and Irwin et al. (2018) (Figure 1). All calibrations agree within 10% with MUSE calibration.

We were able to perform a Minnaert Limb-darkening approximation and produce 2 synthetic spectra (zenith angle = 0º/61.45º) for five distinct sample areas (EZ (Figure 2), SEB, NEB, transition region from EZ to SEB, and from NEB to NTrZ). We performed retrievals using the same a priori atmospheric parameterization as presented in Braude et al. (2020), Pérez-Hoyos et al. (2020) and Anguiano-Arteaga et al. (2021), comparing the retrieved results of each in order to constrain the uncertainties in the Jovian aerosol scheme. To achieve this, we used the NEMESIS (Nonlinear Optimal Estimator for MultivariatE Spectral analySIS) radiative transfer suite (Irwin et al., 2008). We present here the results of this analysis.

Figure 1: Comparison of centre of disk Jupiter spectrum after flux calibration with EZ spectrum from Irwin et al. (2018) and 0º latitude spectrum from Mendikoa et al. (2017).

Figure 2: Observation spectra compared to the obtained synthetic spectra after retrieving the atmospheric parameters for the EZ using Braude et al. (2020) model. Top row corresponds to nadir (incidence and emission angle = 0º) and bottom row to limb (incidence and emission angle = 61.45º). 

Figure 3: Comparison between the a priori aerosol vertical profiles and the retrieved profiles for every region for the model from Braude et al. (2020).

References:

• Carlson, R. W., et al. (2016). Chromophores from photolyzed ammonia reacting with acetylene: Application to Jupiter's Great Red Spot. Icarus, 274, 106–115.
• Sromovsky, L. A., et al. (2017). A possibly universal red chromophore for modeling color variations on Jupiter. Icarus, 291, 232–244.
• Baines, K. H., et al. (2019). The visual spectrum of Jupiter's Great Red Spot accurately modelled with aerosols produced by photolyzed ammonia reacting with acetylene. Icarus, 330, 217–229.
• Pérez-Hoyos, S., et al. (2020). Color and aerosol changes in Jupiter after a North temperate belt disturbance. Icarus, 132, 114021.
• Braude, A. S., et al. (2020). Colour and tropospheric cloud structure of Jupiter from MUSE/VLT: Retrieving a universal chromophore. Icarus, 338, 113589.
• Anguiano-Arteaga, A., et al. (2021). Vertical Distribution of Aerosols and Hazes Over Jupiter's Great Red Spot and Its Surroundings in 2016 From HST/WFC3 Imaging. Journal of Geophysical Research: Planets, 126, e2021JE006996.
• Anguiano-Arteaga, A., et al. (2023). Temporal variations in vertical cloud structure of Jupiter's Great Red Spot, its surroundings and Oval BA from HST/WFC3 imaging. Journal of Geophysical Research: Planets, 128, e2022JE007427.
• Karkoschka, E. (1994). Spectrophotometry of the Jovian Planets and Titan at 300- to 1000-nm Wavelength: The Methane Spectrum. Icarus, 111, 1, 174–192.
• Irwin, P., et al. (2008). The NEMESIS planetary atmosphere radiative transfer and retrieval tool. J. Quant. Spectrosc. Radiat. Transf., 109, 1136–1150.
• Rodgers CD. (2000). Inverse methods for atmospheric sounding: theory and practice. Singapore: World Scientific.
• Cuzzi, J., et al., 2009. Ring Particle Composition and Size Distribution. Springer Netherlands, Dordrecht. pp. 459–509.
• Clark, R.N., McCord, T.B., 1979. Jupiter and Saturn: Near-infrared spectral albedos. Icarus 40, 180–188.
• Mendikoa, I., et al., 2017. Temporal and spatial variations of the absolute reflectivity of Jupiter and Saturn from 0.38 to 1.7 𝜇m with planetcam-upv/ehu. A&A 607, A72.
• Irwin, P.G., et al., 2018. Analysis of gaseous ammonia (NH3) absorption in the visible spectrum of Jupiter. Icarus 302, 426–436

How to cite: Ribeiro, J., Machado, P., Pérez-Hoyos, S., Anguiano-Arteaga, A., and Irwin, P.: Jovian chromophore and upper hazes from CARMENES spectra, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-560, https://doi.org/10.5194/epsc-dps2025-560, 2025.

The composition and formation mechanisms of the compounds responsible for the reddish colouration of Jupiter’s Great Red Spot (GRS) – the so-called chromophores – remain unknown. In recent years, the laboratory-produced chromophore proposed by Carlson et al. (2016) has been shown to satisfactorily reproduce the observed visible spectra not only of the GRS but also of various regions across Jupiter’s disk, with little to no modification (Sromovsky et al., 2017; Baines et al., 2019; Pérez-Hoyos et al., 2020; Braude et al., 2020; Dahl et al., 2021; Fry & Sromovsky, 2023). More recently, Anguiano-Arteaga et al. (2021, 2023) independently retrieved a dominant chromophore agent in the GRS (Figure 1) via radiative transfer modelling of long-term HST/WFC3 observations (225–900 nm), which showed reasonable spectral agreement with the Carlson candidate. The retrieved chromophore particle sizes and column densities were found to be broadly consistent with those reported in earlier GRS studies (e.g., Baines et al., 2019; Braude et al., 2020).

Here, we present results from microphysical modelling of the GRS upper atmosphere (pressures < 1 bar), applying constraints on chromophore mass and particle size derived by Anguiano-Arteaga et al. (2021, 2023). Our simulations, based on the model by Toon et al. (1988), explore the vertical evolution of particle size and distribution (see Figure 2) due to sedimentation, eddy diffusion, and coagulation - following a methodology similar to that of Toledo et al. (2019, 2020) for Uranus and Neptune. These results allow us to constrain the chromophore mass production rates required to maintain a stable, long-lived chromophore layer at the expected levels. This study provides new insights into the origin and persistence of the GRS red colouration.

Figure 1. Illustrative layout of the cloud and haze structure within the Great Red Spot, as retrieved by Anguiano-Arteaga et al. (2023)

Figure 2. Simulated evolution of particle size and vertical distribution in the upper atmosphere of the Great Red Spot, as calculated using the microphysical model described in Toon et al. (1988).

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.

• Anguiano-Arteaga, A., et al. (2023). Temporal variations in vertical cloud structure of Jupiter's Great Red Spot, its surroundings and Oval BA from HST/WFC3 imaging. J. Geophys. Res. Planets, 128, e2022JE007427.

• Baines, K.H., Sromovsky, L.A., Carlson, R.W., Momary, T. W. & Fry, P.M. (2019). The visual spectrum of Jupiter’s Great Red Spot accurately modeled with aerosols produced by photolyzed ammonia reacting with acetylene. Icarus, 330, 217-229.

• Braude, A.S., Irwin, P.G.J., Orton, G.S., & Fletcher, L.N. (2020). Colour and tropospheric cloud structure of Jupiter from MUSE/VLT: Retrieving a universal chromophore. Icarus, 338, 113589.

• 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.

• Dahl, E. K., Chanover, N.J., Orton, G.S., Baines, K.H., … Irwin, P.G.J. (2021). Vertical Structure and Color of Jovian Latitudinal Cloud Bands during the Juno Era. Planet. Sci. J. 2, 16

• Fry, P. M., Sromovsky, L.A. (2023). Investigating temporal changes in Jupiter’s aerosol structure with rotationally-averaged 2015–2020 HST WFC3 images. Icarus, 389, 115224.

• Pérez-Hoyos, S., Sánchez-Lavega, A., Sanz-Requena, J.F., Barrado-Izagirre, N., Carrión-González, O., Anguiano-Arteaga, A., Irwin, P.G.J., & Braude A. S. (2020). Color and aerosol changes in Jupiter after a North Temperate Belt disturbance. Icarus, 132, 114021.

• Sromovsky, L.A., Baines, K.H., Fry, P.M., & Carlson, R.W. (2017). A possibly universal red chromophore for modeling color variations on Jupiter. Icarus, 291, 232-244.

• Toledo, D., Irwin, P. G. J., Rannou, P., Teanby, N. A., Simon, A. A., Wong, M. H., & Orton, G. S. (2019). Constraints on Uranus’s haze structure, formation and transport. Icarus, 333, 1–11.

• Toledo, D., Irwin, P. G. J., Rannou, P., Fletcher, L. N., Teanby, N. A., Wong, M. H., & Orton, G. S. (2020). Constraints on Neptune’s haze structure and formation from VLT observations in the H-band. Icarus, 350, 113808.

• Toon, O. B., Turco, R. P., Westphal, D., Malone, R., & Liu, M. S. (1988). A multidimensional model for aerosols - Description of computational analogs. Journal of Atmospheric Sciences, 45, 2123–2143.

How to cite: Anguiano-Arteaga, A., Perez-Hoyos, S., and Sanchez-Lavega, A.: Formation Constraints on Jupiter’s Great Red Spot chromophore from Microphysical Modelling, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-565, https://doi.org/10.5194/epsc-dps2025-565, 2025.

Recent analyses of wind measurements obtained from tracking cloud motions in spacecraft images of Jupiter and Saturn[1,2] indicate that nonlinear scale-to-scale transfers of kinetic energy act from small to large scales over a wide range of length scales, much as anticipated for 2D or geostrophic turbulence paradigms. At the smallest resolvable scales, however, there is evidence in observations of a forward (downscale) transfer, at least at low and middle latitudes on Jupiter, much like in the Earth’s atmosphere. Moreover, the upscale transfers at the largest spatial scales are evidently dominated by spectrally non-local, highly anisotropic eddy-zonal interactions associated with the generation of intense zonal jets and equatorial super-rotation by direct eddy-zonal flow exchanges. Most analyses to date have emphasised the global mean interactions for both planets, thereby focusing on the spatially homogeneous and isotropic components of the turbulence. Here we present some new analyses of spectral energy transfers on both Jupiter and Saturn that resolve variations in latitude[cf 3], thereby shedding new light on non-homogeneous aspects of jovian turbulent interactions. The results indicate significant variability and inhomogeneity between different locations, with a clear distinction between the tropics, the extratropical middle latitudes and the polar regions. We discuss these in light of other observations and models of gas giant circulation and related laboratory experimental analogues.

[1] Antu˜nano, A., del Río-Gaztelurrutia, T., Sánchez-Lavega, A., & Hueso, R. (2015) Dynamics of Saturn’s polar regions. J. Geophys. Res.: Planets, 120 , 155–176. doi:10.1002/2014JE004709
[2] Read, P. L., Antu˜nano, A., Cabanes, S., Colyer, G., del Río-Gaztelurrutia, T., Sánchez-Lavega, A. (2022). Energy exchanges in Saturn’s polar regions from
Cassini observations: Eddy-zonal flow interactions. J. Geophys. Res., 127 , e2021JE006973. https://doi.org/10.1029/2021JE006973
[3] Chemke, R., & Kaspi, Y. (2015). The latitudinal dependence of atmospheric jet scales and macroturbulent energy cascades. J. Atmos. Sci., 72 , 3891–3907. doi: 10.1175/JAS-D-15-0007.1

How to cite: Read, P. L., Antunano, A., Bobas, H., Colyer, G., Ding, S., del Río Gaztelurrutia, T., Sanchez-Lavega, A., and Young, R.: Characterising turbulent cascades and zonal jet formation processes from observations of cloud level winds on Jupiter and Saturn, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-1019, https://doi.org/10.5194/epsc-dps2025-1019, 2025.

Moist convection plays a key role in Jupiter’s energy and mass transport [1, 2], yet its distribution and nature remain poorly understood due to conflicting observations from various space- and ground-based instruments. Juno MWR data reveal equatorial enrichment of water and ammonia [3, 4], suggesting strong upwelling, while lightning observations show minimal activity near the equator and increased activity toward the poles [5]. These discrepancies have led to competing theories involving the presence of strong deep wind shear [6], circulation cells [7, 8], and mixed-phase cloud formation [9]. Disentangling these requires detailed knowledge of Jupiter’s deep atmospheric structure (such as the deep wind and thermal structure and the spatial distribution of condensing species), which is challenging to obtain via remote sensing alone.

In this work, we aim to address these degenerate results by simulating the jovian atmosphere using the Explicit Planetary hybrid-Isentropic Coordinate (EPIC, [10]) model. We use the new convective parameterization alongside the existing cloud microphysics scheme [11, 12] to model the convection across the planet. We vary the deep atmospheric wind shear and the water abundance to test how these parameters affect the nature and strength of convection in our model. Using these models, we investigate and compare the spatial distribution of convection in our models with those observed by both the Juno MWR and lightning data. 

Our results (Figure 1) show that the locations of strong convection are driven by the presence of a “moisture front” [13], whereby the advection of moisture-rich air into a drier region results in an increase in convective potential, which leads to convection. This has been observed along meso-scale (or larger) convective storms [14] and is consistent with observations of strong convection tied to locations to steep volatile gradients. Increasing the deep wind shear increases the eddy mixing across the gradient through the generation of baroclinic instabilities.

Figure 1: Integrated water cloud density (left) and water vapor mixing ratio at 4 bars (right) along with the associated wind field at 4 bar and the water vapor convergence in red, at day 110 into the model. Note how both the turbulence and the meridional volatile gradient increases with wind shear (parameterized by m in our model), increasing the strength of convection in the atmosphere. Increased convection results in thicker and denser clouds in the zone (northern half of the region).

Here, we will present our results from varying the deep wind shear and the water abundance. We will derive constraints on the degenerate properties by comparing our modeled atmosphere to the observed data, and present possible theories to reconcile the contrasting observed nature of convection.

References

[1] Gierasch, P. J. et al. Nature, 403, 628-630. 2000

[2] Showman, A. P. Journal of the Atmospheric Sciences, 64, 3132. 2007

[3] Li, C. et al. Nature Astronomy, 4, 609-616. 2020

[4] Moeckel, C. et al. Planetary Science Journal, 4, 25. 2023

[5] Brown, S. et al. Nature, 558, 87-90. 2018

[6] Fletcher, L. N. et al. Journal of Geophysical Research (Planets), 126,e06858. 2021

[7] Duer, K. et al. Geophysics Research Letters, 48, e95651. 2021

[8] Fletcher, L. N. et al. Space Science Reviews, 216, 30. 2020

[9] Guillot, T. et al. Journal of Geophysical Research (Planets), 125, e06403. 2020

[10] Dowling, T. E. et al. Icarus, 182, 259-273. 2006

[11] Palotai, C. et al. Icarus, 194, 303-326. 2008

[12] Sankar, R. et al. Icarus, 380, 114973. 2022

[13] Sankar, R. et al. Planetary Science Journal, in press. 2025

[14] Brueshaber, S. R. et al. Icarus, 432, 116465. 2025

How to cite: Sankar, R., Wong, M., and Palotai, C.: Dynamical sources of jovian moist convection, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-1106, https://doi.org/10.5194/epsc-dps2025-1106, 2025.

The Jovian deep water abundance is an important quantity in planetary formation theories that serves as a proxy for Jupiter’s evolution during the early Solar System. The in-situ measurement of this quantity made by the Galileo probe showed that Jupiter’s atmosphere was significantly depleted in oxygen than previously expected (Seiff et al., 1996). However, it is believed that the measurement was made in a Jovian “hot spot” (Orton et al., 1998), which is a region where there is a lack of water clouds (Wong et al., 2004). As a result, the Galileo probe’s measurement of ~0.3x Solar oxygen enrichment has remained contested. Subsequent estimates of the water content made using the Microwave Radiometer (MWR) instrument on-board the Juno spacecraft, particularly in the equatorial region of the planet showed that the planet is enriched in oxygen (Li et al., 2024)., in contrast to the subsolar enrichment obtained by its predecessor spacecraft.

Measurements of disequilibrium chemical species, such as carbon monoxide (CO), phosphine (PH₃), and germane (GeH₄) have been tied to Jupiter’s deep water abundance as they serve as tracers for the compositional make-up of the deeper troposphere (e.g., Wang et al., 2015, 2016). Conventionally, 1D chemical-diffusion models have been employed to simulate the behavior of these trace chemical species in hydrogen-rich atmospheres to constrain the deep water abundance using tropospheric measurements. However, such models are limited in their treatment of the atmosphere as all dynamical behavior is assumed to be constrained via the eddy mixing coefficient, K_zz (Zhang & Showman, 2018).

Here, we present the results of our hydrodynamical cloud-resolving model with simplified thermochemistry to showcase the effects of hydrodynamical and microphysical processes on the abundances of these disequilibrium trace species (Hyder et al., 2025). Using updated chemical timescales, we demonstrate that a deep water abundance of ~2.5x Solar is needed to match the CO observations made near the lifting condensation level. We also find that PH₃ and GeH₄ can be used to place upper bounds on the water content, limiting it to a range of 2.5-5.0x Solar. Our results show that this coupled approach can explain the observations made by the Juno MWR instrument near the equatorial region, supporting the case for a supersolar abundance oxygen in the Jovian troposphere.

References:

• Seiff, A., “Structure of the Atmosphere of Jupiter: Galileo Probe Measurements”, Science, vol. 272, no. 5263, pp. 844–845, 1996.
• Orton, G. S., et al. “Characteristics of the Galileo probe entry site from Earth-based remote sensing observations”, Journal of Geophysical Research, vol. 103, no. E10, pp. 22791–22814, 1998.
• Wong, M. H., Mahaffy, P. R., Atreya, S. K., Niemann, H. B., and Owen, T. C., “Updated Galileo probe mass spectrometer measurements of carbon, oxygen, nitrogen, and sulfur on Jupiter”, Icarus, vol. 171, no. 1, pp. 153–170, 2004.
• Li, C., “Super-adiabatic temperature gradient at Jupiter's equatorial zone and implications for the water abundance”, Icarus, vol. 414, Art. no. 116028, 2024.
• Wang, D., Gierasch, P. J., Lunine, J. I., and Mousis, O., “New insights on Jupiter's deep water abundance from disequilibrium species”, Icarus, vol. 250, pp. 154–164, 2015.
• Wang, D., Lunine, J. I., and Mousis, O., “Modeling the disequilibrium species for Jupiter and Saturn: Implications for Juno and Saturn entry probe”, Icarus, vol. 276, pp. 21–38, 2016.
• Zhang, X. and Showman, A. P., “Global-mean Vertical Tracer Mixing in Planetary Atmospheres. I. Theory and Fast-rotating Planets”, The Astrophysical Journal, vol. 866, no. 1, Art. no. 1, IOP, 2018.
• Hyder, A., Li, C., Chanover, N., and Bjoraker, G., “A supersolar oxygen abundance supported by hydrodynamic modelling of Jupiter's atmosphere”, Nature Astronomy, vol. 9, pp. 211–220, 2025.

How to cite: Hyder, A., Orton, G., Li, C., Chanover, N., and Bjoraker, G.: Hydrodynamical and Chemical Modeling of Jupiter's Atmosphere – Updates on the Deep Water Abundance, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-1907, https://doi.org/10.5194/epsc-dps2025-1907, 2025.

Recent measurements from the Juno spacecraft have revived interest in the possible existence of a radiative zone within Jupiter's atmosphere. If such a layer exists, it would create a stably stratified region, estimated to extend up to 2000 km, challenging the traditional view of a predominantly convective envelope associated with the planet’s zonal jet streams, which penetrate approximately 3000 km. In this study, we explore the potential effects of this radiative zone on Jupiter’s jet stream properties and gravity field. Combining gravity measurement constraints with numerical simulations of a shallow atmospheric model representative of Jupiter, we investigate the dynamical implications of a radiative layer. Our analysis evaluates how the presence of this zone could alter atmospheric dynamics, offering new insights into the planet’s internal structure and questioning the hypothesis of a fully convective dynamical layer. Additionally, through gravity data analysis, we assess whether the existence of such a radiative zone is feasible within Jovian conditions. These findings highlight the importance of considering layered atmospheric models in planetary data interpretation. Moreover, the presence of a radiative zone could be a common feature in other planetary systems and exoplanets, underscoring the need for further research into planetary atmospheres and interiors and their broader implications for planetary science.

How to cite: Duer-Milner, K., Siebenaler, L., and Miguel, Y.: Implications of a Radiative Zone on Jupiter’s Gravity Field and Atmospheric Dynamics, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-699, https://doi.org/10.5194/epsc-dps2025-699, 2025.

In giant planet atmospheres, carbon monoxide (CO) can originate either from internal sources, such as thermochemical processes, or from external sources, such as meteorite impacts.

A dual origin of CO has already been inferred on Jupiter through infrared spectroscopy [1], and on Neptune via submillimeter spectroscopy [2,3]. For both planets, these studies concluded that stratospheric CO primarily originated from external sources, namely large cometary impacts—the most recent being the collision of comet Shoemaker-Levy 9 (SL9) with Jupiter in 1994 [4–8], along with an internal source. In contrast, the origin of CO in Saturn's atmosphere remains uncertain. Observations of the vertical distribution of CO in Saturn’s atmosphere are consistent with a cometary source approximately 220 years ago [9–11], although an internal origin cannot be ruled out, particularly given the potential influence of H₂O photochemistry on the vertical CO profile. The specific contribution of material infalling from the rings, both in the equatorial and mid-latitude regions remain also to be estimated.

Observed on May 25, 2018 using ALMA (project 2017.1.00636.S), maps of HCN (5-4) and CO (3-2) lines have been obtained with a combination of seven pointings of the main array in configuration C43.2, complemented by three pointings of the ACA to mosaic the full disk of the planet. Together with the HCN line, the CO line observed by ALMA is detected at the limb of the planet only, from the equator up to the south and north polar regions, with a latitudinal resolution about 2°, and both were initially used to provide the first absolute wind measurements in Saturn's stratosphere [12]. These analyses have revealed variations in the width of the CO line across the entire limb, suggesting that information on the vertical distribution of Saturn’s CO is accessible—potentially shedding light on its external or internal origin. Here, we will present the retrieved CO stratospheric abundances from 25°S to the northern polar regions resulting from different initial condition setups (preliminary results with an apriori CO profile as constant for a volume mixing ratio of 10^-8 are shown in the figure, and at the observation date, Saturn southern hemisphere was masked by its rings). We test the sensibility of the retrieved abundances to the CO prior and temperature profiles. We will also discuss the retrieved abundances in the context of the ring material infalling from the rings detected in situ by Cassini [13,14], and compare our results with photochemical model calculations taking into account ring material influx in Saturn’s neutral and ionized atmosphere [15].

[1] Bézard et al. (2022, Icarus 159, 95–111)

[2] Lellouch et al. (2005, A&A 430, L37–L40)

[3] Hesman et al. (2007, Icarus 186, 342–353)

[4] Lellouch et al. (1995, Nature 373, 592–595)

[5] Lellouch et al. (1997, Planet. Space Sci. 45, 1203–1212)

[6] Moreno et al. (2003, Planet. Space Sci. doi:10.1016/S0032-0633(03)00072-2)

[7] Griffith et al. (2004, Icarus)

[8] Lellouch et al. (2006, Icarus doi:10.1016/j.icarus.2006.05.018.

[9] Cavalié et al. (2009, Icarus 203, 531–540)

[10] Cavalié et al. (2008, A&A 484, 555–561)

[11] Cavalié et al. (2010, A&A 510, A88)

[12] Benmahi et al. (2022, A&A 666, A117)

[13] Moore et al. (2018, Geophysical Research Letters, Volume 45, Issue 18, pp. 9398-9407)

[14] Waite et al. (2018, Science, Volume 362, Issue 6410, id.aat2382)

[15] Moses et al. (2023, Icarus, Volume 391, article id. 115328)

How to cite: Bardet, D., Fouchet, T., Cavalié, T., Moreno, R., Lellouch, E., Benmahi, B., and Guerlet, S.: Saturn’s stratospheric carbon monoxide abundance observed with ALMA, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-512, https://doi.org/10.5194/epsc-dps2025-512, 2025.

The composition and isotopic ratios in different bodies of the solar system are important tracers of their formation and of the primordial composition and physical/chemical conditions of the protoplanetary disk. Numerous measures have been performed these past 50 years in meteorites (Meibom et al. 2007), comets (Rousselot et al. 2014), and in giant planets atmospheres (Owen and Encrenaz 2003 and many others). They show a variety of values compared to the solar ones (Marty et al. 2011). Measuring the abundances and the isotopic ratios in the giant planets is of prime interest as they should reflect the initial composition of the solar nebula and the properties of the disk from which they were formed (Marboeuf et al. 2018).

One way to assess this is to look at the ¹²C/¹³C and ¹⁵N/¹⁴N isotopic ratios. The relative abondance of ¹⁵N in N-bearing species is a strong indicator of the formation processes of the giant planets, because it gives hints on the abundances of N₂ and NH₃, the two major N-bearing species in the solar system. The ¹⁵N/¹⁴N ratio from NH₃ in Jupiter’s and Saturn’s atmospheres was found to be close to solar (Fouchet et al. 2000, Fletcher et al. 2014), implying that the main contributor of primordial N in the two planets atmospheres was N₂ which is expected to present a low ¹⁵N enrichment in the solar nebula (Fletcher et al. 2014). The ¹²C/¹³C ratio in hydrocarbons is also close to solar in the giant planets’ atmospheres (Niemann et al. 1998, Orton et al. 1992, Combes et al. 1979 and others).

However, the atmospheres of the giant planets are subject to drastic changes as they constantly interact with their surroundings. A major example was in July 1994 with the comet Shoemaker-Levy 9 (SL9) impacts in Jupiter’s atmosphere, which led to altered atmospheric composition and anomalous isotopic ratios (Matthews et al. 2002). New molecules previously undetected were brought/produced in Jupiter’s stratosphere, presumably by shock-induced chemistry (Zahnle et al. 1995), such as HCN (Marten et al. 1995). Matthews et al. 2002 found that the post-impact ¹²C/¹³C and ¹⁴N/¹⁵N isotopic ratios in HCN were super-terrestrial, respectively with a mean increase factor of 3 and 10, probably indicating an unusual cometary composition depleted in ¹³C and ¹⁵N.

In this paper, we present new derivations of the ¹²C/¹³C and ¹⁵N/¹⁴N isotopic ratios in Jupiter’s atmosphere from HCN observations. We used the Atacama Large Millimeter/submillimeter Array (ALMA) observations of Jupiter at two lines of two HCN isotopes, H¹³CN at 345.34 GHz and HC¹⁵N at 344.20 GHz. This dataset is part of project 2016.1.01235.S that was taken in March 22, 2017, i.e., almost 23 years after SL9 impacts. With a radiative transfer code, we derive the vertical abundance profiles of the two isotopes and we give new estimates of the ¹²C/¹³C and ¹⁵N/¹⁴N isotopic ratios in the stratosphere of Jupiter using the vertical profile of HCN derived in Cavalié et al. (2023). We compare our new derivations 1) with the intriguing post-SL9 values of Matthews et al. (2002) to confirm their findings or to trace any evolution of the isotopic ratios 23 years after SL9 impacts; and 2) more generally with the last 50 years observations of the atmosphere of Jupiter and of other solar system objects to better understand isotopic ratios in the giant planets.

References:

Cavalié et al. 2023, Nature Astronomy, Volume 7, p. 1048-1055

Combes et al. 1979, Icarus, Volume 39, Issue 1, p. 1-27

Fletcher et al. 2014, Icarus, Volume 238, p. 170-190

Fouchet et al. 2000, Icarus, Volume 143, Issue 2, pp. 223-243

Marboeuf et al. 2018, Monthly Notices of the Royal Astronomical Society, Volume 475, Issue 2, p.2355-2362

Marten et al. 1995, Geophysical Research Letters, Volume 22, Issue 12, p. 1589-1592

Matthews et al. 2002, The Astrophysical Journal, Volume 580, Issue 1, pp. 598-605

Meibom et al. 2007, The Astrophysical Journal, Volume 656, Issue 1, pp. L33-L36

Niemann et al. 1998, Journal of Geophysical Research, Volume 103, Issue E10, p. 22831-22846

Orton et al. 1992, Icarus, Volume 100, Issue 2, p. 541-555

Owen and Encrenaz 2003, Space Science Reviews, v. 106, Issue 1, p. 121-138

Rousselot et al. 2014, The Astrophysical Journal Letters, Volume 780, Issue 2, article id. L17, 5 pp.

Zahnle et al. 1995, Geophysical Research Letters, Volume 22, Issue 12, p. 1593-1596

How to cite: Lefour, C., Cavalié, T., Moreno, R., Lellouch, E., Fouchet, T., and Hartogh, P.: A new derivation of the 12C/13C and 15N/14N isotopic ratios in the stratosphere of Jupiter revealed by ALMA, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-248, https://doi.org/10.5194/epsc-dps2025-248, 2025.

Saturn's upper atmosphere is dominated by two main processes: the planetary aurora, which encircle the polar regions, and the influx of material from the rings, known as "ring rain." To observe the upper atmosphere, we measure the spectral emission lines of the major ionospheric ion H₃⁺, which are observable from Earth through key atmospheric windows using large infrared telescopes. Over the last few decades, these ion emissions have been used to determine the ion's temperature and density, mainly within the auroral region where emissions are brightest. In prior work on Saturn's aurora, we found that the southern aurora was warmer than the northern near equinox in 2011, likely due to magnetic field asymmetries, and that auroral power/density/temperature in general is modulated by Saturn's `planetary period oscillation' phenomenon. In previous work on Saturn's ring rain, we estimated the ring mass influx to the planet to be on the order of 432-2870 kg/second, which, if constant, would result in the rings demise within hundreds of millions of years. In the several years that followed these Saturn upper atmosphere results, the planets auroral and global temperature appeared to fall by approximately 100 Kelvin for presently unknown reasons, preventing our ability to probe the region, as the signal to noise ratio fell too low.

Here, we will present new results from a new observing campaign with the Keck telescope in late 2024, using the upgraded NIRSPEC instrument. Saturn’s upper atmosphere appears to have warmed again to the point that we are now able to detect H₃⁺ emission from not only the auroral region, but the mid-latitude region in which ring rain falls, allowing us to study both. This talk will discuss our new results on temperature variability in the auroral region in both hemispheres simultaneously and add a new derivation of the ring rain influx. 

How to cite: O'Donoghue, J., Moore, L., Melin, H., Owens, M., Agiwal, O., and Stallard, T.: Saturn's upper atmosphere: auroras and 'ring rain' using new H3+ observations with Keck, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-751, https://doi.org/10.5194/epsc-dps2025-751, 2025.

Several types of atmospheric waves can be found in the atmospheres of the Solar System planets. They are an important atmospheric phenomenon because they can modify the mean structure of the atmosphere and affect the general circulation [1]. Gravity waves are a common type of atmospheric wave. They can have different origins and cover a large range of spatial scales. Gravity waves are able to transport energy and momentum through different atmospheric layers, thus indicating the great importance of understanding their effects on the atmospheric dynamics.

Observations of temperatures of the Giant Planets have shown that their upper atmospheres (thermospheres) are hundreds of Kelvins hotter than would be expected from solar heating alone [2]. The existing numerical models have had difficulties to reproduce the observed temperature structures, particularly at mid and low latitudes. It has been long thought that waves propagating vertically from below play an important role in shaping the thermal structure of thermospheres. One of the mechanisms proposed to heat thermospheres is the heating produced by dissipating waves [3, 4], but this effect seems to be at least a factor of two lower than needed on Saturn [2]. Another mechanism is the weakening of the intense high-latitude westward jets, thereby allowing the meridional transport of energy trapped in the polar regions [5, 6]. Recently, the detection of gravity waves in Saturn's thermosphere has been reported using data from Cassini INMS and UVIS occultation data [5, 6, 7].

The Saturn Thermosphere-Ionosphere Model (STIM) is a 3D general circulation model used to study the dynamics, energy balance and gas structure of Saturn's upper atmosphere under the external influences of solar radiation and magnetospheric forcing [8, 9]. The model couples dynamically and chemically the thermosphere and the ionosphere, including the drag produced by the collisions between ions and neutral species, and Joule heating. In this work we show high resolution numerical simulations of Saturn's upper atmosphere performed using the STIM model to explore the effects of gravity waves in the circulation of Saturn's thermosphere. We force the bottom of the model (near 3 Pa) to explore the propagation of waves resolved by the model through the thermosphere, their characteristics and impact on the circulation. We also explore the effects of smaller scale gravity waves by adapting the gravity wave drag parameterization of [10] to Saturn.

References:

[1] Vallis. Atmospheric and Ocean Fluid Dynamics. Cambridge University Press, Cambridge, UK, 2006.

[2] Strobel et al. Saturn's Variable Thermosphere. Saturn in the 21^st Century. Cambridge University Press, Cambridge, UK, 2019.

[3] Young et al. Gravity waves in Jupiter's thermosphere. Science, 276, 1997.

[4] O’Donoghue et al. Heating of Jupiter's upper atmosphere above the Great Red Spot. Nature, 536, 2016.

[5] Müller-Wodarg et al. Atmospheric Waves and Their Possible Effect on the Thermal Structure of Saturn's Thermosphere. Geophysical Research Letters, 46, 2019.

[6] Brown et al. Evidence for gravity waves in the thermosphere of Saturn and implications for global circulation. Geophysical Research Letters, 49, 2022.

[7] Brown et al. A pole-to-pole pressure-temperature map of Saturn's thermosphere from Cassini Grand Finale data. Nature Astronomy, 4, 2020.

[8] Müller-Wodarg et al. A global circulation model of Saturn's thermosphere. Icarus, 180, 2006.

[9] Müller-Wodarg et al. Magnetosphere-atmosphere coupling at Saturn: 1 – Response of thermosphere and ionosphere to steady state polar forcing. Icarus, 221, 2012.

[10] Yiğit et al. Parameterization of the effects of vertically propagating gravity waves for thermosphere general circulation models: Sensitivity study. Journal of Geophysical Research, 113, 2008.

How to cite: Iñurrigarro, P., Medvedev, A. S., and Müller-Wodarg, I. C. F.: Simulations of gravity waves in Saturn's thermosphere., EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-1083, https://doi.org/10.5194/epsc-dps2025-1083, 2025.

The primary source of heating in the upper atmospheres (thermospheres) of giant planets has been subject of long debate. The conundrum (or 'energy crisis') consists in  observed thermosphere temperatures at low and mid latitudes exceeding values expected from solar heating by several hundred Kelvins (Yelle and Miller, 2004), suggesting the presence of another energy source. Several theories have been proposed to explain the high temperatures, from heating by upward propagating gravity or acoustic waves  (Young et al., 1997; Matcheva et al., 1999; Schubert et al., 2003) to heating of auroral regions by magnetosphere-atmosphere coupling (Yelle and Miller, 2004; Mueller-Wodarg et al., 2019). While the latter provides sufficient energy, the problem became one of global energy redistribution. On a rapidly rotating planet, Coriolis forces act to 'trap' auroral energy in the polar regions, heating up the poles but leaving the equator cold (Smith et al., 2007; 2009; Mueller-Wodarg et al., 2019). On Saturn, the redistribution of energy from pole to equator was achieved by invoking zonal Rayleigh drag, possibly related to atmospheric waves (Mueller-Wodarg et al., 2019). Using a new General Circulation Model of Jupiter, we reproduce well the observed low and mid latitude thermosphere temperatures without the need to invoke Rayleigh drag. We identify for the first time the role played by a planet's magnetic field in affecting the global energy redistribution in thermospheres.

How to cite: Müller-Wodarg, I., Iñurrigarro, P., Moore, L., Koskinen, T., and Medvedev, A.: Temperatures of Jupiter's and Saturn's Upper Atmospheres: The role of the Planetary Magnetic Field, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-1421, https://doi.org/10.5194/epsc-dps2025-1421, 2025.