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Moon-magnetosphere interactions result from the encounter between a magnetospheric plasma flow and moons, which act as obstacles to the plasma flow. In the Jovian magnetosphere, the Galilean moons orbit with a Keplerian velocity much slower than the plasma velocity, driven in near corotation by the planetary magnetic field. Therefore, they disturb the magnetospheric plasma flow, which in turn generates Alfvén waves in their close environments. These waves propagate along the magnetic field lines, accelerating particles and triggering auroral emissions in the giant planet atmosphere.Since August 2016, the Juno mission has made it possible to characterize in-situ the moon-magnetosphere interactions. Several crossings of the flux tubes connected to the orbits of the Galilean moons have been reported, revealing a diversity of particle properties and acceleration processes. However, Europa-magnetosphere interaction, whose remote and in-situ signatures are weaker and more difficult to identify than those of Io, remain poorly known.We characterize the precipitating electrons accelerated in the Europa-magnetosphere interaction by analyzing in-situ measurements and remote sensing observations recorded during 10 crossings of the flux tubes connected to Europa's auroral footprint tail by Juno. The electron downward energy flux exhibits an exponential decay as a function of down-tail distance from Europa's main auroral spot, with an e-folding factor of 7.2°. Electrons are accelerated at energies between 0.3 and 25 keV, with a characteristic energy that decreases down‐tail. We show that in the near tail (∆λFrac < 6°), acceleration is due, at least in part, to electrostatic processes while in the far tail (∆λFrac > 6°) broadband energy spectra are evidence for Alfvénic acceleration. The size of the interaction region at the equator is estimated to be 4.5 Europa radii, consistent with previous estimates based on theory and UV observations.

The electromagnetic coupling between the Galilean satellites at Jupiter and the planetary ionosphere generates an auroral footprint, whose ultimate source is the relative velocity between the moons and the corotating magnetospheric plasma. The footprint can be detected in the infrared L band (3.3-3.6 microns) by the Jovian InfraRed Auroral Mapper (JIRAM) onboard the Juno spacecraft, which can observe the footprint position with high precision. Here, we report the JIRAM data acquired since August 27th 2016 until May 23rd 2022, corresponding to the first 42 orbits of Juno. The dataset is used to compute the average position of the footprint tracks of Io, Europa and Ganymede. The result of the present analysis can help to test the reliability of magnetic field models, to calibrate ground-based observations and to highlight episodes of variability in the footprint positions, which in turn can point out specific conditions of the Jovian magnetospheric environment.

Reflected sunlight observations from the Ultraviolet Spectrograph (UVS) on the Juno spacecraft were used to study the distribution of acetylene (C$_2$H$_2$) at Jupiter's south pole. We find that the shape of the C$_2$H$_2$ absorption feature varies significantly across the polar region, and this can be used to infer spatial variability in the C$_2$H$_2$ abundance. There is a localized region of enhanced C$_2$H$_2$ absorption which coincides with the location of Jupiter's southern polar aurora; the C$_2$H$_2$ abundance poleward of the auroral oval is a factor of 3 higher than adjacent quiescent, non-auroral longitudes. This builds on previous infrared studies which found enhanced C$_2$H$_2$ abundances within the northern auroral oval. This suggests that Jupiter's upper-atmosphere chemistry is being strongly influenced by the influx of charged auroral particles and demonstrates the necessity of developing ion-neutral photochemical models of Jupiter's polar regions., Accepted in JGR: Planets

Jupiter hosts very intense auroral emissions, which originates from various magnetospheric processes. One of these emissions is associated with the orbital motion of the innermost Galilean satellite Io, which orbits at ~5.9 RJ from Jupiter’s centre (1 RJ = 71492km). At that distance, the magnetospheric plasma is forced to corotation by the strong planetary magnetic field. Therefore Io, which orbits at a slower speed than the corotating plasma, is continuously swept by both the plasma and the Jovian magnetic field. The relative velocity between Io and the plasma triggers a perturbation that propagates along the magnetic field lines and towards the ionosphere as Alfvén waves. Along their way, the Alfvén waves can accelerate electrons into the planetary atmosphere, where they ultimately generate an auroral emission called the Io footprint. The position of the Io footprint depends on the speed of the Alfvén waves, which in turn depends on the magnetic field geometry and magnitude as well as on the plasma mass distribution around Io, whose sulfur-dioxide-rich atmosphere constantly supply a dense cloud of plasma around Jupiter, called the Io Plasma Torus.In 2016, Juno reached the Jupiter system and, since then, the Jovian InfraRed Auroral Mapper (JIRAM) has been observing the infrared emission associated with the Io footprint with a spatial resolution of ~ few tens of km/pixel. Thanks to the high resolutions of JIRAM, we report evidences of variability in the Io footprint position that are not related to the System III (i.e: the frame corotating with Jupiter) longitude of Io. Using a model for the plasma distribution of the Io Plasma Torus and the magnetic field, we quantitatively determine the state of the plasma distribution corresponding the JIRAM observations. This is the first attempt to retrieve quantitative information on the torus variability by using the Io footprint position. The best-fit plasma density and temperature are consistent with previous observations and analysis of the Io Plasma Torus from the Voyager 1, Voyager 2, Cassini, Galileo and Hisaki spacecrafts. Besides, we found that both density and temperature can exhibit remarkable non-System III variability, which can be ascribed either to local time asymmetry of the plasma in the Io torus or to temporal variation in the torus mass loading.

The localized delivery of new long-lived species to Jupiter’s stratosphere by comet Shoemaker-Levy 9 in 1994 opened a window to constrain jovian chemistry and dynamics by monitoring the evolution of their vertical and horizontal distributions. ALMA observations of HCN and CO in March 2017 show that CO was meridionally uniform and restricted to pressures lower than 3±1 mbar. HCN shared a similar vertical distribution in the low-to-mid latitudes, but was surprisingly depleted at pressures higher than 0.04(-0.03; +0.07) mbar in the polar regions. We propose that heterogeneous chemistry bonds HCN on large aurora-produced aerosols at these pressures in the jovian polar regions causing the observed depletion. We also propose that a relatively small fraction of CO causes enhanced production of CO2 inside the aurora to explain the long-term decrease of the CO column density and the CO2 peak observed only at southern polar latitudes in 2000.

Jupiter's stratospheric chemistry and dynamics are poorly understood as a function of latitude. The Shoemaker-Levy 9 comet impacts in Jupiter's atmosphere in 1994 have offered us with a unique means to characterize Jupiter's stratospheric chemistry and dynamics. We can indeed use the delivery at 44°S of the long-lived species HCN, CO, H2O, and CS and the subsequent temporal evolution of their spatial distribution as constraints for vertical and meridional mixing, zonal winds and chemistry as a function of latitude. We mapped HCN and CO in Jupiter's stratosphere with ALMA in March 2017. These observations have already been used in Cavalié et al. (2021) and Benmahi et al. (2021) to derive the stratospheric zonal wind field. In this paper, we use the same observations to retrieve the vertical and meridional distributions of HCN and CO, almost 25 years after the comet impacts. We will present the spatial distributions of both species and discuss the implications on Jupiter's stratospheric chemistry, and vertical and horizontal mixing.

Being mostly connected via closed magnetic field lines, the aurorae at the two poles display two broadly similar signatures of the same magnetospheric processes. However, differences are sometimes observed, indicative of asymmetries either in the polar regions (e.g. different solar illumination, magnetic anomalies, etc.) or in the magnetosphere (e.g. twisting of the magnetotail), thus showing two complementary sides of the magnetosphere-ionosphere coupling.Whatever the planet, seeing the aurorae on both poles at the same time is challenging. Either both polar regions can be seen at once, but then only from the side, with poor spatial coverage (especially close and beyond the limb), or we need (at least) two observatories. Here we use the latter option to observe the two faces of the UV aurorae on Jupiter. In the last years, several Hubble Space Telescope observations with the Space Telescope Imaging Spectrograph (STIS) have been planned during close-up perijove observations of the poles with the UV spectrograph (UVS) on board the Juno spacecraft. The aurorae at Jupiter can be divided into three main components, with the Main Emissions, a quasi-continuous, but sometimes irregular, ribbon of auroral emissions, delimitating the outer emissions outside of it and the polar emissions inside of it. We compare the global morphology and the relative power emitted by the different auroral features in these three regions. Former studies also indicated that synchronized quasi-periodic flares could be observed in both hemispheres and we will look after similar events in this new dataset. Finally, even if the observations are delayed by approximately one hour, we can still compare the mean emitted power before (north) and after (south) each Juno perijove to look for a global trend.

Jupiter hosts intense auroral activity associated with charged particles precipitating into the planet's atmosphere. The Galilean moons orbiting within the magnetosphere are swept by the magnetic field: the resulting perturbation travels along field lines as Alfven waves, which are able to accelerate electrons towards the planet, producing satellite-induced auroral emissions. These emissions due to the moons, known as footprints, can be detected in various wavelengths (UV, visible, IR) outside the main auroral emission as multiple bright spots followed by footprint tails. Since 2016 the Juno spacecraft orbiting Jupiter has surveyed the polar regions more than 30 times at close distances. Onboard the spacecraft, the Jovian InfraRed Auroral Mapper (JIRAM) is an imager and spectrometer with an L-band imaging filter suited to observe auroral features at unprecedented spatial resolution. JIRAM revealed a rich substructure in the footprint tails of Io, Europa and Ganymede, which appear as a trail of quasi-regularly spaced bright sub-dots whose intensity fades away along the emission trail as the spatial separation from the footprint increases. The fine structure of the Europa and Ganymede footprint tails is reported in this work for the first time. We will also show that the typical distance between subsequent sub-dots is the same for all three moons at JIRAM resolution in both hemispheres. In addition, the sub-dots observed by JIRAM are static in a frame corotating with Jupiter. A feedback mechanism between the ionosphere and the magnetosphere is suggested as a potential candidate to explain the morphology of the footprint tails.

The UVS instrument on the Juno mission records far-ultraviolet reflected sunlight from Jupiter. These spectra are sensitive to the abundances of chemical species in the upper atmosphere and to the distribution of the stratospheric haze layer. We combine observations from the first 30 perijoves of the mission in order to study the meridional distribution of acetylene (C$_2$H$_2$) in Jupiter's stratosphere. We find that the abundance of C$_2$H$_2$ decreases towards the poles by a factor of 2-4, in agreement with previous analyses of mid-infrared spectra. This result is expected from insolation rates: near the equator, the UV solar flux is higher, allowing more C$_2$H$_2$ to be generated from the UV photolysis of CH$_4$. The decrease in abundance towards the poles suggests that horizontal mixing rates are not rapid enough to homogenize the latitudinal distribution., Accepted in JGR Planets. 19 pages, 3 figures

Observational data of Titan's atmosphere composition, gathered in particular by the Cassini mission, allow accessing latitudinal, longitudinal and temporal variations of the altitudinal profiles of several species. While 1D models are a powerful tool to gain insight into the chemistry occurring in Titan's atmosphere, they cannot capture the four-dimensional nature of these processes at the same time. However, due to the large extent of the atmosphere and the complexity of chemistry, global 2D and 3D models with the chemical complexity of 1D models do not exist yet. On the way of developing a 2D photochemical model of Titan, including the very complex chemical schemes used in 1D models and also taking latitudinal variations into account, we developed an ultraviolet radiative transfer model to compute the actinic flux in a 2D geometry. We found that photolysis rates calculated in classical plane-parallel models to derive the rates in mean conditions give results notably different from a model that calculates the mean rates with a 2D geometry. We demonstrate that the introduction of the 2D geometry affects significantly the density profiles on both neutrals and ions, especially on nitriles. As a consequence, we advocate using radiative transfer model in 2D geometry from now on to interpret the wide diversity of observational data about Titan's atmosphere (pending the emergence of 2D models with complex chemical schemes).

Since 30 years, an equatorial oscillation of the temperature structure with a quasi-period of 4 years has been discovered in the atmosphere of Jupiter (Orton et al. 1991, Leovy et al. 1991). This phenomenon results in a complex vertical and horizontal structure of prograde and retrograde jets. However, the wind structure of the stratosphere in the equatorial zone of Jupiter has not been measured directly. It has only been inferred in the tropical region from the thermal wind balance using temperatures measured in the jovian stratosphere and the cloud-top wind speeds measured as a initial condition (e.g. Flasar et al. 2004). But temperatures are not constrained between the upper troposphere and the middle stratosphere from observations, limiting thus the accuracy of the thermal wind balance. In this study, we derive self-consistently for the first time the structure of the tropical winds by utilizing wind and temperature observations all performed in the stratosphere. The wind speeds were obtained by Cavalié et al. (2021) at 1 mbar in Jupiter's stratosphere in both the equatorial and tropical regions in March 2017 with ALMA. The stratospheric thermal field was measured a few days before from the equator to the mid-latitudes with Gemini/TEXES (Giles et al. 2020). For the derivation of the wind, we use both the thermal wind equation (Pedlosky 1979) and the equatorial thermal wind equation (Marcus et al. 2019). In this paper, we will present and discuss our results.

Jupiter’s aurora is complex and dynamic, with a large number of distinct auroral features and regions generated by multiple phenomena. Of these features, Io’s auroral signature is one of the most persistent and identifiable aurora, with a rich observational history spanning decades of remote observations. Since Juno arrived at Jupiter, providing in-situ transits through flux tubes directly connected to Io’s auroral emissions, its diverse set of instruments have revealed an even more complex and dynamic picture of Io’s auroral interaction. In this presentation, we report on Juno observations of precipitating electron fluxes connected to 18 crossings of Io’s footprint tail aurora, over altitudes of 0.15 to 1.1 Jovian radii (RJ). We will highlight how the strength of precipitating electron fluxes is dominantly organized by “Io-Alfvén tail distance”, the angle along Io’s orbit between Io and an Alfvén wave trajectory connected to the tail aurora. We will discuss how these fluxes were best fit with an exponential as a function of down-tail extent with an e-folding distance of 21˚, the acceleration region altitude likely increases down-tail, and most of the parallel electron acceleration sustaining the tail aurora occurs above 1 RJ in altitude. Finally, we will highlight how Juno has likely transited Io’s Main Alfvén Wing fluxtube, observing a characteristically distinct signature with precipitating electron fluxes ~600 mW/m2 and an acceleration region extending as low as 0.4 RJ in altitude.

The Alfven wave mode transmits field‐aligned currents and large‐scale turbulence throughout Jupiter's magnetosphere. Magnetometer data from the Juno spacecraft have provided the first observations of Alfvenic fluctuations along the polar magnetic flux tubes connected to Jupiter's main auroral oval and the Jovian satellites. Transverse magnetic field perturbations associated with Io are observed up to ~90° away from main Io footprint, supporting the presence of extended Alfvenic wave activity throughout the Io footprint tail. Additional broadband fluctuations measured equatorward of the statistical auroral oval are composed of incompressible magnetic turbulence that maps to Jupiter's equatorial plasma sheet at radial distances within ~20 R(sub J). These fluctuations exhibit a k(sub ||) power spectrum consistent with strong magnetohydrodynamic turbulence. This turbulence can generate up to ~100 mW/m(exp 2) of Poynting flux to power the Jovian aurora in regions connected to the inner magnetosphere's central plasma sheet.

The two main ultraviolet-signatures resulting from the Io-magnetosphere interaction are the local auroras on Io's atmosphere, and the Io footprints on Jupiter. We study here how Io's daily eclipses ...

Context. The tropospheric wind pattern in Jupiter consists of alternating prograde and retrograde zonal jets with typical velocities of up to 100 m/s around the equator. At much higher altitudes, in the ionosphere, strong auroral jets have been discovered with velocities of 1-2 km/s. There is no such direct measurement in the stratosphere of the planet. Aims. In this paper, we bridge the altitude gap between these measurements by directly measuring the wind speeds in Jupiter's stratosphere. Methods. We use the Atacama Large Millimeter/submillimeter Array's very high spectral and angular resolution imaging of the stratosphere of Jupiter to retrieve the wind speeds as a function of latitude by fitting the Doppler shifts induced by the winds on the spectral lines. Results. We detect for the first time equatorial zonal jets that reside at 1 mbar, i.e. above the altitudes where Jupiter's Quasi-Quadrennial Oscillation occurs. Most noticeably, we find 300-400 m/s non-zonal winds at 0.1 mbar over the polar regions underneath the main auroral ovals. They are in counter-rotation and lie several hundreds of kilometers below the ionospheric auroral winds. We suspect them to be the lower tail of the ionospheric auroral winds. Conclusions. We detect directly and for the first time strong winds in Jupiter's stratosphere. They are zonal at low-to-mid latitudes and non-zonal at polar latitudes. The wind system found at polar latitudes may help increase the effciency of chemical complexification by confining the photochemical products in a region of large energetic electron precipitation., 7 pages and 3 figures (+ 5 pages and 5 figures for the appendix). Published in A&A 647, L8

The upper tropospheric zonal winds have been measured since decades using cloud tracking with maximum winds speeds of ∼ 100 m/s in the tropical region (Ingersoll et al. 1979). Juno measurements have shown that these winds extend in the deep layers of the planet (Kaspi et al. 2018). In the ionosphere, jets have been detected in the auroral zone with velocities of 1-2 km/s (Rego et al. 1999). In-between these atmospheric regions, in the stratosphere, there are no such tracers as clouds. Even if zonal winds can in principle be indirectly derived from temperature field by assuming the thermal wind balance (e.g. Flasar et al. 2004), this technique relies on a boundary condition often taken as the cloud-top structure which is located at levels that are separated from where the stratospheric temperature field is constrained. Also, this technique breaks down at equatorial latitudes.Using the Atacama Large Millimeter/submillimeter Array, we mapped Jupiter’s stratospheric HCN emission in March 2017 to directly measure wind-induced Doppler shifts on the spectral lines. We imaged the HCN limb emission with an angular resolution of 1” and a very high spectral resolution. After subtracting the rapid rotation of the planet from the Doppler shifts measured on the spectral lines, we derived the wind speeds as a function of latitude on both limbs.We find strong tropical jets at 1 mbar with velocities of 100-200 m/s lying atop the layers where the Quasi-Quadrennial Oscillation occurs. Most surprisingly, we find strong non-zonal winds in Jupiter’s polar regions at 0.1 mbar with counter-rotation velocities of 300-400 m/s. Their position coincides with the location of the main auroral oval.In this paper, we will present our observations and results. We will also discuss their implications on the dynamics and chemistry of Jupiter’s stratosphere.

The stratosphere of Jupiter is subject to an equatorial oscillation of its temperature structure with a quasi-period of 4 years (Orton et al. 1991, Leovy et al. 1991) which could result in a complex vertical and horizontal structure of prograde and retrograde jets. Yet, the stratospheric wind structure in Jupiter’s equatorial zone has never been directly measured. It has only been inferred in the tropical region from the thermal wind balance using temperature measurements in the stratosphere and the cloud-top wind speeds as a boundary condition (Flasar et al. 2004). However, the temperatures are not well-constrained between the upper troposphere and the middle stratosphere from the observations.In this paper, we obtain for the first time an auto-consistent determination of the tropical wind structure using wind and temperature measurements all performed in the stratosphere. The wind speeds have been measured by Cavalié et al. (submitted) at 1 mbar in the stratosphere of Jupiter in the equatorial and tropical zone in March 2017 with ALMA. The stratospheric thermal field was measured five days apart in the low-to-mid latitudes with the IRTF/TEXES instrument (Giles et al. 2020). For the wind derivation, we use the thermal wind equation (Pedlosky, 1979) and equatorial thermal wind equation (Marcus et al. 2019). We will present and discuss our results.This paper is a follow-up to the EGU21-8726 paper.

Dawn storms are among the brightest events in the Jovian aurorae. Up to now, they had only been observed from Earth-based observatories, only showing the Sun-facing side of the planet. Here we show...

We present multi-instrument Juno observations on day-of-year 86, 2017 that link particles and fields in Jupiter’s polar magnetosphere to transient UV emissions in Jupiter’s northern auroral region known as dawn storms. Juno ranged from 42ºN - 51ºN in magnetic latitude and 5.8 – 7.8 jovian radii (1 RJ = 71,492 km) during this period. These dawn storm emissions consisted of two separate, elongated structures which extended into the nightside, rotated with the planet, had enhanced brightness (up to at least 1.4 megaRayleigh) and high color ratios. The color ratio is a proxy for the atmospheric penetration depth and therefore the energy of the electrons that produce the UV emissions. Juno observed electrons and ions on magnetic field lines mapping to these emissions. The electrons were primarily field-aligned, bi-directional, and, at times, exhibited sudden intensity decreases below ∼10 keV coincident with intensity enhancements up to energies of ∼1000 keV, consistent with the high color ratio observations. The more energetic electron distributions had characteristic energies of ∼160 – 280 keV and downward energy fluxes (∼70 – 135 mW/m2) that were a significant fraction needed to produce the UV emissions for this event. Magnetic field perturbations up to ∼0.7% of the local magnetic field showing evidence of upward and downward field-aligned currents, whistler mode waves, and broadband kilometric radio emissions were also observed along Juno’s trajectory during this timeframe. These high latitude observations show similarities to those in the equatorial magnetosphere associated with dynamics processes such as interchange events, plasma injections, and/or tail reconnection.

The UVS instrument on the Juno mission recorded transient bright emission from a point source in Jupiter's atmosphere. The spectrum shows that the emission is consistent with a 9600-K blackbody located 225 km above the 1-bar level and the duration of the emission was between 17 ms and 150 s. These characteristics are consistent with a bolide in Jupiter's atmosphere. Based on the energy emitted, we estimate that the impactor had a mass of 250-5000 kg, which corresponds to a diameter of 1-4 m. By considering all observations made with Juno UVS over the first 27 perijoves of the mission, we estimate an impact flux rate of 24,000 per year for impactors with masses greater than 250-5000 kg., Comment: Accepted in GRL. 21 pages, 3 figures

Since the 1950s, quasi-periodic oscillations have been studied in the terrestrial equatorial stratosphere. Other planets of the solar system present (or are expected to present) such oscillations, like the Jupiter Equatorial Oscillation(JEO) and the Saturn Semi-Annual Oscillation (SSAO). In Jupiter's stratosphere, the equatorial oscillation of its relative temperature structure about the equator, is characterized by a quasi-period of 4.4 years. The stratospheric wind field in Jupiter's equatorial zone has never been directly observed. In this paper, we aim at mapping the absolute wind speeds in Jupiter's equatorial stratosphere to quantify vertical and horizontal wind and temperature shear. Assuming geostrophic equilibrium, we apply the thermal wind balance using nearly simultaneous stratospheric temperature measurements between 0.1 and 30 mbar performed with Gemini/TEXES and direct zonal wind measurements derived at 1 mbar from ALMA observations, all carried out between March 14th and 22nd, 2017. We are thus able to calculate self-consistently the zonal wind field in Jupiter's stratosphere where the JEO occurs. We obtain stratospheric map of the zonal wind speeds as a function of latitude and pressure about Jupiter's equator for the first time. The winds are vertically layered with successive eastward and westward jets. We find a 200 m/s westward jet at 4 mbar at the equator, with a typical longitudinal variability on the order of ~50 m/s. By extending our wind calculations to the upper troposphere, we find a wind structure qualitatively close to the wind observed using cloud-tracking techniques. Nearly simultaneous temperature and wind measurements, both in the stratosphere, are a powerful tool for future investigations of the JEO (and other planetary equatorial oscillations) and its temporal evolution., Comment: the article was accepted on July 12, 2021

11 transient bright flashes were detected in Jupiter's atmosphere using the UVS instrument on the Juno spacecraft. These bright flashes are only observed in a single spin of the spacecraft and their brightness decays exponentially with time, with a duration of ~1.4 ms. The spectra are dominated by H2 Lyman band emission and based on the level of atmospheric absorption, we estimate a source altitude of 260 km above the 1-bar level. Based on these characteristics, we suggest that these are observations of Transient Luminous Events (TLEs) in Jupiter's upper atmosphere. In particular, we suggest that these are elves, sprites or sprite halos, three types of TLEs that occur in the Earth's upper atmosphere in response to tropospheric lightning strikes. This is supported by visible light imaging, which shows cloud features typical of lightning source regions at the locations of several of the bright flashes. TLEs have previously only been observed on Earth, although theoretical and experimental work has predicted that they should also be present on Jupiter., Comment: Accepted in JGR: Planets. 28 pages, 8 figures

Ionospheric conductance is important in controlling the electrical coupling between the Jovian planetary magnetosphere and its ionosphere. To some extent, it regulates the characteristics of the ionospheric current from above and the closure of the magnetosphere-ionosphere circuit in the ionosphere (Cowley&Bunce, 2001). Multi-spectral images collected with the UltraViolet Spectrograph (UVS) (Gladstone et al., 2017) on board Juno (Bagenal et al.,2017) have been analyzed to derive the spatial distribution of the auroral precipitation reaching the atmosphere (Bonfond et al., 2017). Electron energy flux and their characteristic energy have been used as inputs to an ionospheric model providing the production and loss rates of the main ion species, H3+, hydrocarbon ions and electrons (Gérard et al., 2020). Their steady state densities are calculated and used to determine the local distribution of the Pedersen electrical conductivity and its altitude integrated value for each UVS pixel. These values are displayed as H3+ density and Pedersen conductivity maps. We find that the main contribution to the Pedersen conductance corresponds to collisions of H3+ and hydrocarbon ions with H2.Analysis of the Birkeland current intensities based on the Juno magnetometers measurements (Kotsiaros et al. 2019) indicated that the observed current intensities are statistically larger in the south. They suggested that these differences are possibly due to a higher Pedersen conductance in this hemisphere. In order to verify this hypothesis, we calculate the conductance and H3+ density maps for perijoves 1 to 15 based on Juno-UVS spectral images. We compare the spatially integrated auroral conductance values of the two hemispheres for each orbit. The objective is to identify possible hemispheric asymmetries. REFERENCESBagenal, F., et al. (2017). Magnetospheric science objectives of the Juno mission. Space Science Reviews, 213(1-4), 219-287.Bonfond, B., et al. (2017). Morphology of the UV aurorae Jupiter during Juno's first perijove observations. Geophysical Research Letters, 44(10), 4463-4471.Cowley, S.W.H. & Bunce, E.J. (2001). Origin of the main auroral oval in Jupiter’s coupled magnetosphere–ionosphere system. Planet. Space Sci. 49, 1067–1088.Gérard et al., Spatial distribution of the Pedersen conductance in the Jovian aurora from Juno-UVS spectral images, J. Geophys. Res., in press.Gladstone et al. (2017). The ultraviolet spectrograph on NASA’s Juno mission. Space Science Reviews, 213(1-4), 447-473.Kotsiaros, S. et al. (2019). Birkeland currents in Jupiter’s magnetosphere observed by the polar-orbiting Juno spacecraft. Nature Astronomy, 3(10), 904-909.

In July 1994, comet Shoemaker-Levy 9 collided with Jupiter. This has introduced new chemical species into Jupiter’s atmosphere, notably H2O. We observed the disk-averaged emission H2O in Jupiter’s stratosphere at 556.936 GHz between 2002 and 2019 with the Odin space telescope with the initial goal of better constraining vertical eddy mixing (Kzz) in the layers probed by our observations (0.2-5 mbar). The Odin observations show a decrease of about 40% of the line emission from 2002 to 2019. We analyzed these observations by combining a 1D photochemical model with a radiative transfer model to constrain the vertical eddy diffusion Kzz in the stratosphere of Jupiter. We were able to reproduce this decrease by modifying a well-established Kzz profile, in the 0.2 mbar to 5 mbar pressure range. However, the Kzz obtained is incompatible with observations of the main hydrocarbons. We found that even if we increase locally the initial abundances of H2O and CO at impact, the photochemical conversion of H2O and CO to CO2 does not allow us to find the observed decrease of the H2O emission line over time, suggesting that there is another loss mechanism. We propose that auroral chemistry, not accounted for in our model, as a promising candidate to explain the loss of H2O seen by Odin. Modeling the temporal evolution of the chemical species deposited by comet SL9 in the atmosphere of Jupiter with a 2D photochemical model would be the next step in this study.

In July of 2016, NASA began a new era in Jupiter exploration by placing the Juno spacecraft and its highly capable suite of scientific instrumentation in a polar orbit about Jupiter. It was a unique opportunity to study Jupiter’s auroras in great details with the Ultraviolet Spectrograph (UVS) instrument during the first 25 perijoves. Here we present a systematic analysis of a newly identified feature of the polar emissions called the auroral bright spot. The bright spots have power ranging from tens to a hundred gigawatts. In a given perijove, bright spot reoccurs at almost the same system III (SIII) position within a time interval of a few to tens of minutes. Furthermore, we found a brightness quasiperiodicity of 22-28 minutes in the southern bright spots observed during perijove 4 and perijove 16. The northern bright spots locate in a confined region, near 175° SIII longitude and 65 degrees latitude, while the southern spots scatter randomly around the pole. The bright spots’ positions reported here are usually located on the edge of the swirl region (the polar-most region of Jupiter’s auroras). This feature is observed at all magnetic local times rather than being confined to the noon sector. Therefore, the bright spot is incompatible with the auroral signature of Earth-like Sun-facing cusp, as proposed in earlier works. However, due to Jupiter's rapid rotation with respect to the size of the magnetosphere, the topology of the cusp region at Jupiter is expected to be considerably complicated by the twisting of the field lines. Hence, we cannot conclude whether the bright spot is related to the Jovian cusp processes yet. Finally, we also have identified time intervals during which Juno flew through the field lines connected to the bright spot allowing further investigations of the associated particles and responsible processes.

International audience; We report the first in situ observations of electron measurements at a Europa footprint tail (FPT) crossing in the auroral region. During its 12th science perijove pass, Juno crossed magnetic field lines connected to Europa's FPT. We find that electrons in the range ~0.4 to ~25 keV, with a characteristic energy of 3.6 ± 0.5 keV, precipitate into Jupiter's atmosphere to create the footprint aurora. The energy flux peaks at ~36 mW/m2, while the peak ultraviolet (UV) brightness is estimated at 37 kR. We estimate the peak electron density and temperature to be 17.3 cm-3 and 1.8 ± 0.1 keV, respectively. Using magnetic flux shell mapping, we estimate that the radial width of the interaction at Europa's orbit spans roughly 3.6 ± 1.0 Europa radii. In contrast to typical Io FPT crossings, the instrument background caused by penetrating energetic radiation (> ~5-10 MeV electrons) increased during the Europa FPT crossing.

Uranus and Neptune are the least-explored planets in our Solar System. This paper summarizes mysteries about these incredibly intriguing planets and their environments spurred by our limited observations fromVoyager 2and Earth-based systems. Several of these observations are either inconsistent with our current understanding built from exploring other planetary systems, or indicate such unique characteristics of these Ice Giants that they leave us with more questions than answers. This paper specifically focuses on the value of all aspects of magnetospheric measurements, from the radiation belt structure to plasma dynamics to coupling to the solar wind, through a future mission to either of these planets. Such measurements have large interdisciplinary value, as demonstrated by the large number of mysteries discussed in this paper that cover other non-magnetospheric disciplines, including planetary interiors, atmospheres, rings, and moons.