Peio Iñurrigarro

Saturn has a unique long-lived, nearly stationary hexagon wave close to its north pole that is coupled to an intense eastward jet. Despite decades of observation, no similar wave has been reported so far in the southern hemisphere or elsewhere on Saturn. Ground-based and Hubble Space Telescope (HST) images obtained in 2025 revealed the presence of a decagonal wave at planetographic latitudes ∼58°S to 63°S. HST images in 2023 and 2024 showed vertices with weaker albedo contrasts and linear sides of the decagon, implying an evolving phenomenon. The decagon moves eastward with a velocity of 2.5 meters per second, much slower than the zonal jet at 60.5°S with 116 meters per second, and the longitudes of its vertices oscillate with a period of 32 days and amplitudes of 4.6° to 8.4°. From its properties, the decagon could be a large-scale meandering wave trapped vertically and confined meridionally by the dominant jet curvature. Shallow water model simulations suggest that the decagon may have originated from a spatially periodic disturbance in the jet peak or may have been driven by a dark anticyclonic vortex immediately to the north.

Jupiter’s upper atmosphere (mesosphere/thermosphere/ionosphere) is driven primarily by its interaction with the magnetosphere which maps an electric potential into the magnetic polar region and is accompanied by energetic electron precipitation into the upper atmosphere. While the latter significantly contributes towards the ionospheric densities, the former generates westward accelerations at auroral latitudes and a transfer of angular momentum from atmosphere to magnetosphere as well as local Joule heating. In-situ solar heating is insignificant in the upper atmosphere, but the solar ionization plays a key role especially at non-auroral latitudes. Over the past years, we have developed the Jupiter Thermosphere Ionosphere Model (JTIM) (Mueller-Wodarg et al., 2025) to numerically calculate this time-dependent coupling and test the sensitivity of the global atmosphere system to forcing from the magnetosphere interaction. With JTIM, we calculate the global dynamics and redistribution of energy. Most recently, we have updated the JTIM model with more realistic electric potentials from the BATSrU model (Sarkango et al., 2019) and electron impact ionization rates from the Jupiter Auroral Ionosphere Code (JAIC) (Nichols et al., 2026). We will present latest simulations and compare with available observations. Our calculations allow us to better understand the underlying physical processes in this complex system, including the role of coupling with the deeper atmosphere and global distribution and transport of angular momentum as well as variability of the entire system.

Saturn has a unique long-lived, nearly stationary hexagon wave close to its north pole that is coupled to an intense eastward jet. Despite decades of observation, no similar wave has been reported so far in the southern hemisphere or elsewhere on Saturn. Ground-based and Hubble Space Telescope (HST) images obtained in 2025 revealed the presence of a decagonal wave at planetographic latitudes ~ 58°S - 63°S. HST images in 2023 and 2024 showed vertices with weaker albedo contrasts and linear sides of the decagon, implying an evolving phenomenon. The decagon moves eastwards with a velocity of 2.5 m/s relative to System III radio-rotation period, much slower than the zonal jet centered at latitude of 60.5°S that has a peak velocity of 116 m/s. Simultaneously, the position in longitude of its vertices oscillate relative to the mean motion with an average period of 32 days and amplitudes of 4.6°-8.4°. The decagon could be a quasi-geostrophic Rossby wave trapped vertically and confined meridionally by the dominant jet curvature with an intrinsic phase speed of -113 ms-1. Saturn’s new decagon offers a rare opportunity to probe polar jet dynamics and the processes that create stable polygonal flows in giant planets, including Jupiter’s polar cyclones arranged in polygonal patterns in a weak wind field beyond 80° latitude.

The Juno mission, in orbit around Jupiter since July 2016, has provided an unprecedented view of the planet’s atmospheric dynamics. High-resolution images from the JunoCam camera aboard Juno have led to the identification of small-scale compact cloud formations known as pop-up clouds [1], which appear as elevated features projecting shadows over their surrounding clouds. These features are distinguished from large-scale strong convective outbreaks by their smaller spatial and vertical scales [2, 3], suggesting they are powered by the less vigorous ammonia moist convection [4]. A compact cluster of clouds of this type was also observed within the Great Red Spot in the very high-resolution images from JunoCam [5]. While deep convective phenomena can have large vertical extents reaching altitudes of a few tens of kilometers above the main cloud deck [6], recent studies suggest that pop-up clouds rise to around 15 km above their immediate surroundings [4].In this work, we used JunoCam high-resolution images to conduct a morphological classification of these small-scale moist convection pop-up clouds across a wide range of latitudes and dynamical environments, including Folded Filamentary Regions (FFRs), vortex interiors, vortex peripheries, and others. In addition, we performed a comprehensive morphological characterization of these features, employing a Geographic Information System (GIS) framework [7] with a geodetic metric, based on an oblate spheroid model defined by Jupiter’s radius and flattening parameter. Our results show that pop-up clouds are present across all latitudes covered by JunoCam and exhibit significant spatial clustering. The morphological classification highlights a variety of shapes, from compact cells and cloud-clusterings to elongated filaments. Measurements reveal varying horizontal scales but consistent separations within individual clusters. Furthermore, we also studied vertical elevations derived from projected shadows, which remained below 15 km above the surrounding cloud deck. References[1] Hansen et al. (2019). JunoCam Images of Castellanus Clouds on Jupiter. AGU Fall Meeting Abstracts, 2019, P44A-05. https://ui.adsabs.harvard.edu/abs/2019AGUFM.P44A..05H [2] Orton et al. (2022). Investigating Relative Cloud Heights in Jupiter Using Juno's JunoCam Imager. AAS/Division for Planetary Sciences Meeting Abstracts #54, 54, 306.06. https://ui.adsabs.harvard.edu/abs/2022DPS....5430606O [3] Guillot et al. (2024). How high are Jupiter's clouds? From high-resolution JunoCam images to a multi-wavelength analysis. EGU24. doi:10.5194/egusphere-egu24-17351 [4] Palotai et al. (2023). Moist convection in the giant planet atmospheres. Remote Sensing, 15, 219. doi:10.3390/rs15010219 [5] Sánchez-Lavega A. et al. (2018), The rich dynamics of Jupiter’s Great Red Spot from JunoCam – Juno images, Astronomical J., 156, 162 (9pp), doi:10.3847/1538-3881/aada81 [6] Sánchez-Lavega et al. (2008). Depth of a strong jovian jet from a planetary-scale disturbance driven by storms. Nature, 451 (7177), 437–440. doi:10.1038/nature06533 [7] Trent M. Hare, Angelo P. Rossi, Alessandro Frigeri, Chiara Marmo. Interoperability in planetary research for geospatial data analysis, Planetary and Space Science, Volume 150, 2018, ISSN 0032-0633, https://doi.org/10.1016/j.pss.2017.04.004

The high-resolution images of Jupiter obtained by the Junocam instrument on the Juno mission show a wide range of small-scale compact clouds suggestive of active convection. These features have horizontal sizes of 10-50 km and have been named in the recent literature as pop-up clouds because of their morphological characteristics [1]. The pop-up clouds appear as elevated towers projecting shadows over different meteorological systems [2, 3], and their appearance seems linked to the type of atmospheric region where they develop (in zones such as the South Tropical Zone, in anticyclones including the Great Red Spot, or in cyclones, and Folded Filamentary Regions and polar regions) [4]. Their shadows indicate cloud tops 5-20 km above their environments, although some observations have found more extreme altitudes for some specific pop-up clouds [2, 3]. Although the vertical structure and overall morphology of pop-up clouds suggest they are analogous to Altocumulus Castellanus [1], the lack of evidences of strong divergence at their cloud tops has also led to comparisons with Cumulus Humilis [4]. Compared with strong Jovian convective disturbances [5, 6], pop-up clouds seem to represent less energetic convective storms compatible with ammonia powered moist convection [1, 3-4]. To investigate these clouds we run simulations of moist convective storms using a three-dimensional cloud resolving model at a spatial resolution of 0.5 km. We run several experiments to investigate cloud top altitudes for ammonia moist convection under a variety of ammonia abundances and environmental conditions and we also explore the energetics of these storms. We show that ascending ammonia cumulus clouds over a surrounding homogenous cloud cannot develop large vertical structures compatible with the lengths of the shadows observed. We explore under which conditions ammonia convective storms can ascend to higher levels when forced from below. We also explore the atmospheric conditions in which ammonia pop-up clouds develop isolated over a deeper homogenous NH4SH cloud [3]. References [1] Hansen et al. (2019). JunoCam Images of Castellanus Clouds on Jupiter. AGU Fall Meeting Abstracts, 2019, P44A-05. https://ui.adsabs.harvard.edu/abs/2019AGUFM.P44A..05H [2] Orton et al. (2022). Investigating Relative Cloud Heights in Jupiter Using Juno's JunoCam Imager. AAS/Division for Planetary Sciences Meeting Abstracts #54, 54, 306.06. https://ui.adsabs.harvard.edu/abs/2022DPS....5430606O [3] Guillot et al. (2024). How high are Jupiter's clouds? From high-resolution JunoCam images to a multi-wavelength analysis. EGU24. doi:10.5194/egusphere-egu24-17351 [4] Palotai et al. (2023). Moist Convection in the Giant Planet Atmospheres. Remote Sens. 2023, 15, 219. doi:10.3390/rs15010219 [5] Sánchez-Lavega et al. (2008). Depth of a strong jovian jet from a planetary-scale disturbance driven by storms. Nature, 451(7177), 437–440. doi:10.1038/nature06533 [6] Sánchez-Lavega et al. (2017). A planetary-scale disturbance in the most intense Jovian atmospheric jet from JunoCam and ground-based observations, Geophysical Research Letters, 44, 4679–4686. doi:10.1002/2017GL073421.

Jupiter's most intense jet at planetographic latitude 23.7°N experiences vigorous planetary‐scale disturbances. The onset consists of the outbreak of 1–3 bright clouds of convective origin developing turbulent plumes. Observed events between 1970 and 2025 shows a cycle of activity with a period in the range of 3.8–5.1 yrs interrupted between 1990 and 2007 by a large period of 17.1 yrs without eruptions. The 2020 and 2025 plumes emerged at the anticyclonic and cyclonic sides of the jet, respectively. They undergo meridional migrations and zonal accelerations during the first 2–3 days of their life, moving toward the jet's peak and exceeded its maximum speed. We propose that interactions between the plume vorticity, the background flow in the jet and planetary vorticity force these meridional motions. A combination of solar radiative forcing of the upper troposphere and convective potential energy build‐up at water clouds could generate the cycle.

The primary source of heating in the upper atmospheres (thermospheres) of giant planets has been the subject of long debate. The conundrum (or “energy crisis”) consists in observed thermosphere temperatures at low and midlatitudes exceeding values expected from solar heating by several hundred kelvins, 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 to heating of auroral regions by magnetosphere–atmosphere coupling. While auroral heating provides sufficient energy, the problem becomes 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. On Saturn, the redistribution of energy from poles to equator was recently achieved by invoking Rayleigh drag, possibly related to atmospheric gravity or acoustic waves. Using a new general circulation model of Jupiter, we reproduce well the observed low and midlatitude thermosphere temperatures without the need to invoke Rayleigh drag. Instead, the planet’s magnetic field is strong enough to cause significant ion drag and slowing down zonal winds in the nonauroral thermosphere and allow global energy redistribution. This distinguishes Jupiter from Saturn and most likely the other gas giant planets in our solar system may have implications on extrasolar planets with strong magnetic fields as well.

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 21st 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.

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.

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.