Publications of Denis Grodent
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See detailUltralow-Frequency Waves in Driving Jovian Aurorae Revealed by Observations From HST and Juno
Pan, Dong-Xiao; Yao, Zhong-Hua; Manners, Harry et al

in Geophysical Research Letters (2021), 48(5), 2020091579

Large-scale electrical currents and Alfvénic waves are the two main drivers responsible for producing planetary aurorae. The relative contribution of each process is a central question in terrestrial ... [more ▼]

Large-scale electrical currents and Alfvénic waves are the two main drivers responsible for producing planetary aurorae. The relative contribution of each process is a central question in terrestrial auroral science, and poorly understood for other planets due to the relatively rare opportunity of in-situ spacecraft measurements. Here, we present observations of Jupiter's aurorae from the Hubble Space Telescope (HST) contemporaneous with Juno magnetometer measurements in the magnetosphere. For three successive days, we found that the magnetospheric ultralow-frequency (ULF) wave activity (with periods of 1–60 min) was correlated with auroral power. This was especially true for the Alfvénic modes. We further performed a statistical analysis based on HST visits during Juno's third and seventh orbit, which revealed a systematic correlation between ULF wave and auroral activity. Our results imply that Alfvénic wave power could be an important source in driving Jupiter's aurorae, as theoretically predicted. [less ▲]

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See detailA sublimated water atmosphere on Ganymede detected from Hubble Space Telescope observations
Roth, Lorenz; Ivchenko, Nickolay; Gladstone, G. Randall et al

in Nature Astronomy (2021)

Ganymede’s atmosphere is produced by charged particle sputtering and sublimation of its icy surface. Previous far-ultraviolet observations of the O i 1,356 Å and O i 1,304 Å oxygen emissions were used to ... [more ▼]

Ganymede’s atmosphere is produced by charged particle sputtering and sublimation of its icy surface. Previous far-ultraviolet observations of the O i 1,356 Å and O i 1,304 Å oxygen emissions were used to infer sputtered molecular oxygen (O2) as an atmospheric constituent, but an expected sublimated water (H2O) component remained undetected. Here we present an analysis of high-sensitivity spectra and spectral images acquired by the Hubble Space Telescope revealing H2O in Ganymede’s atmosphere. The relative intensity of the oxygen emissions requires contributions from the dissociative excitation of water vapour, indicating that H2O is more abundant than O2 around the subsolar point. Away from the subsolar region, the emissions are consistent with a pure O2 atmosphere. Eclipse observations constrain atomic oxygen to be at least two orders of magnitude less abundant than these other species. The higher H2O/O2 ratio above the warmer trailing hemisphere compared with the colder leading hemisphere, the spatial concentration in the subsolar region and the estimated abundance of ~1015 molecules of H2O per cm2 are consistent with sublimation of the icy surface as source. [less ▲]

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See detailMorphology of Jupiter's Polar Auroral Bright Spot Emissions via Juno-UVS Observations
Haewsantati, Kamolporn ULiege; Bonfond, Bertrand ULiege; Wannawichian, S. et al

in Journal of Geophysical Research: Space Physics (2021), 126(2), 2020028586

Since 2016, the Juno-UVS (Ultraviolet Spectrograph) instrument has been taking spectral images of Jupiter's auroras in their full extent, including the nightside, which cannot be viewed from Earth. We ... [more ▼]

Since 2016, the Juno-UVS (Ultraviolet Spectrograph) instrument has been taking spectral images of Jupiter's auroras in their full extent, including the nightside, which cannot be viewed from Earth. We present a systematic analysis of features in Jupiter's polar auroras called auroral bright spots, which were observed by Juno-UVS during the first 25 orbits of the spacecraft. An auroral bright spot is an isolated localized and transient brightening in the polar region. Bright spots were identified in 16 perijoves (PJ) out of 24, mostly in either the northern or the southern hemisphere but rarely in both during the same PJ. The emitted power of the bright spots is time variable with peak power ranging from a few tens to a hundred of gigawatts. Moreover, we found that, for some PJs, bright spots exhibit quasiperiodic behavior. The spots, within PJ4 and PJ16, each reappeared within \textless2,000 km from the previous position in System III with periods of 28 and 22 min, respectively. This period is similar to periods previously identified in X-rays and various other observations. The bright spot positions are in a specific region in the northern hemisphere in System III, but are scattered around the magnetic pole in the southern hemisphere, near the edge of the swirl region. Furthermore, the bright spots can be seen at any local time, rather than being confined to the noon sector as previously thought from Earth-based observations. This suggests that the bright spots might not be firmly connected to the noon facing magnetospheric cusp processes. [less ▲]

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See detailJupiter's X-ray aurora during UV dawn storms and injections as observed by XMM-Newton, Hubble, and Hisaki
Wibisono, A. D.; Branduardi-Raymont, G.; Dunn, W. R. et al

in Monthly Notices of the Royal Astronomical Society (2021)

We present results from a multiwavelength observation of Jupiter’s northern aurorae, carried out simultaneously by XMM-Newton, the Hubble Space Telescope (HST), and the Hisaki satellite in September 2019 ... [more ▼]

We present results from a multiwavelength observation of Jupiter’s northern aurorae, carried out simultaneously by XMM-Newton, the Hubble Space Telescope (HST), and the Hisaki satellite in September 2019. HST images captured dawn storms and injection events in the far ultraviolet aurora several times during the observation period. Magnetic reconnection occurring in the middle magnetosphere caused by internal drivers is thought to start the production of those features. The field lines then dipolarize which injects hot magnetospheric plasma from the reconnection site to enter the inner magnetosphere. Hisaki observed an impulsive brightening in the dawnside Io plasma torus (IPT) during the final appearance of the dawn storms and injection events which is evidence that a large-scale plasma injection penetrated the central IPT between 6-9 RJ (Jupiter radii). The extreme ultraviolet aurora brightened and XMM-Newton detected an increase in the hard X-ray aurora count rate, suggesting an increase in electron precipitation. The dawn storms and injections did not change the brightness of the soft X-ray aurora and they did not “switch-on” its commonly observed quasi-periodic pulsations. Spectral analysis of the X-ray aurora suggests that the precipitating ions responsible for the soft X-ray aurora were iogenic and that a powerlaw continuum was needed to fit the hard X-ray part of the spectra. The spectra coincident with the dawn storms and injections required two powerlaw continua to get good fits. [less ▲]

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See detailJupiter's Double-Arc Aurora as a Signature of Magnetic Reconnection: Simultaneous Observations From HST and Juno
Guo, Ruilong ULiege; Yao, Zhonghua ULiege; Grodent, Denis ULiege et al

in Geophysical Research Letters (2021), 48(14), 93964

Jupiter's powerful auroral emission is usually divided into the polar, main, and equatorward components. The driver of Jupiter's main aurora is a central question for the community. Previous ... [more ▼]

Jupiter's powerful auroral emission is usually divided into the polar, main, and equatorward components. The driver of Jupiter's main aurora is a central question for the community. Previous investigations reveal many distinct substructures on the main auroral oval, which are indicators of fundamentally different magnetospheric processes. Understanding these substructures could provide key constraints for uncovering the driver of Jupiter's main aurora emission. In this study, we show the evolution of a double-auroral arc on the dawnside from observations by the Hubble Space Telescope (HST). Simultaneous in situ observations from the Juno spacecraft provide direct evidence of magnetic reconnection and magnetic dipolarization. By analyzing the datasets from Juno and HST, we suggest that the evolution of the double-arc structure is likely a consequence of the non-steady progress of magnetic reconnection. [less ▲]

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See detailOn the location of the CH4 homopause at Jupiter's mid-to-high latitudes
Sinclair, James; Irwin, Patrick; Bézard, Bruno et al

in 43rd COSPAR Scientific Assembly. Held 28 January - 4 February (2021)

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See detailA Statistical Survey of Low Frequency Magnetic Fluctuations at Saturn
Pan, Dong-Xiao; Yao, Zhong-Hua; Guo, Rui-Long et al

in Journal of Geophysical Research. Space Physics (2021), 126(2), 28387

Low-frequency waves are closely related to magnetospheric energy dissipation processes. The Cassini spacecraft explored Saturn's magnetosphere for over 13 years, until September 2017, covering a period of ... [more ▼]

Low-frequency waves are closely related to magnetospheric energy dissipation processes. The Cassini spacecraft explored Saturn's magnetosphere for over 13 years, until September 2017, covering a period of more than a complete solar cycle. Using this rich heritage data set, we systematically investigated key physical parameters of low-frequency waves in Saturn's magnetosphere, including their local time distribution and the dependence on solar activity. We found that the wave activity peaked in the near noon sector. For the nightside, the wave intensity also appeared to peak pre and postmidnight. Due to the limited local time coverage for each solar phase, we were not able to draw a firm conclusion on the wave's dependence on solar activity. In general, the wave power showed a monotonically decreasing trend toward larger distances in nightside sectors especially during the declining phase, which implied that low-frequency waves mainly originate from the relatively inner regions of the magnetosphere. On the dayside, stronger waves were mostly located at/within ∼25 Rs, near the magnetopause. The study shows a global picture of low-frequency waves in Saturn's magnetosphere, providing important implications for how magnetospheric energy dissipates into Saturn's polar ionosphere and atmosphere. [less ▲]

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See detailJupiter's X-ray aurora during a mass injection and Io mass loading events observed by XMM-Newton, Hubble, and Hisaki
Wibisono, Affelia; Branduardi-Raymont, Graziella; Dunn, Will et al

in EGU General Assembly Conference Abstracts (2021)

Voyager 1 detected the first extra-terrestrial UV auroral emissions when it explored the Jupiter system in 1979 while the planet’s X-ray aurora was discovered later that year by the Einstein Observatory ... [more ▼]

Voyager 1 detected the first extra-terrestrial UV auroral emissions when it explored the Jupiter system in 1979 while the planet’s X-ray aurora was discovered later that year by the Einstein Observatory. Electrons are accelerated into Jupiter’s atmosphere near the poles and excite native molecular and atomic hydrogen. These then release UV photons after returning to the ground state. The same population of precipitating electrons can also emit high energy (>2 keV) X-ray photons by bremsstrahlung to produce Jupiter’s hard X-ray aurora. At higher latitudes and within the oval of UV and hard X-ray emissions is where the more diffuse UV and low energy (<2 keV) soft X-ray aurorae are found. Charge exchange processes between precipitating ions and neutrals in the gas giant planet’s atmosphere are responsible for the soft X-ray emissions. Simultaneous observations of Jupiter’s UV and X-ray aurorae were carried out by the Hubble Space Telescope (HST), Hisaki satellite and XMM-Newton in September 2019 to support Juno’s 22nd perijove. Images of the northern far UV aurora by HST showed internally driven dawn storms and injection events occurring at least twice during the observation period. These features are thought to be caused by magnetic reconnection happening in the middle magnetosphere. This subsequently leads to the dipolarization of the field lines which injects hot magnetospheric plasma from the middle to the inner magnetosphere. Hisaki saw an impulsive brightening in the Io plasma torus on the day of the second event showing that there was indeed a large-scale injection that penetrated the central torus in the inner magnetosphere. At this time, the northern aurora brightened in both extreme UV and hard X-ray, which suggests that there was an increase in electron precipitation. There was no response from the soft X-ray aurora, and no quasi-periodic pulsations, often observed in the auroral emissions, were detected during either of the events. X-ray spectral analysis reveals that the precipitating ions were iogenic. We conclude that we have witnessed two cases of mass injection in the Jovian inner magnetosphere due to Io mass loading events. [less ▲]

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See detailSimultaneous Observations of the Jovian Auroras using Juno-UVS and HST-STIS during Perijoves 4-7
Kammer, Joshua; Davis, Michael; Levin, Steven et al

in 43rd COSPAR Scientific Assembly. Held 28 January - 4 February (2021)

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See detailHow Jupiter’s unusual magnetospheric topology structures its aurora
Zhang, Binzheng; Delamere, Peter A.; Yao, Zhonghua ULiege et al

in Science Advances (2021), 7(15), 1204

Jupiter’s bright persistent polar aurora and Earth’s dark polar region indicate that the planets’ magnetospheric topologies are very different. High-resolution global simulations show that the ... [more ▼]

Jupiter’s bright persistent polar aurora and Earth’s dark polar region indicate that the planets’ magnetospheric topologies are very different. High-resolution global simulations show that the reconnection rate at the interface between the interplanetary and jovian magnetic fields is too slow to generate a magnetically open, Earth-like polar cap on the time scale of planetary rotation, resulting in only a small crescent-shaped region of magnetic flux interconnected with the interplanetary magnetic field. Most of the jovian polar cap is threaded by helical magnetic flux that closes within the planetary interior, extends into the outer magnetosphere, and piles up near its dawnside flank where fast differential plasma rotation pulls the field lines sunward. This unusual magnetic topology provides new insights into Jupiter’s distinctive auroral morphology. Jupiter’s slow dayside magnetic merging and fast rotation produce an unusual magnetic topology that can explain its polar aurora. Jupiter’s slow dayside magnetic merging and fast rotation produce an unusual magnetic topology that can explain its polar aurora. [less ▲]

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See detailDetection of a Bolide in Jupiter's Atmosphere With Juno UVS
Giles, Rohini S.; Greathouse, Thomas K.; Kammer, Joshua A. et al

in Geophysical Research Letters (2021), 48(5), 2020091797

The Ultraviolet Spectrograph (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 ... [more ▼]

The Ultraviolet Spectrograph (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 250–5,000 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 250–5,000 kg. [less ▲]

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See detailAre Dawn Storms Jupiter's Auroral Substorms?
Bonfond, Bertrand ULiege; Yao, Zhonghua ULiege; Gladstone, G. R. et al

in AGU Advances (2021), 2(1), 2020000275

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 for ... [more ▼]

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 for the first time global views of the phenomenon, from its initiation to its end and from the nightside of the aurora onto the dayside. Based on Juno's first 20 orbits, some patterns now emerge. Small short-lived spots are often seen a couple of hours before the main emission starts to brighten and evolve from a straight arc to a more irregular one in the midnight sector. As the whole feature rotates dawn-ward, the arc then separates into two arcs with a central initially void region that is progressively filled with emissions. A gap in longitude then often forms before the whole feature dims. Finally, it transforms into an equatorward-moving patch of auroral emissions associated with plasma injection signatures. Some dawn storms remain weak and never fully develop. We also found cases of successive dawn storms within a few hours. Dawn storms thus share many fundamental features with the auroral signatures of the substorms at Earth, despite the substantial differences between the dynamics of the magnetosphere at the two planets. [less ▲]

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See detailRecent observations of Jupiter's aurora and airglow emissions by Juno-UVS
Gladstone, Randy; Kraft, Ralph; Levin, Steven et al

in 43rd COSPAR Scientific Assembly. Held 28 January - 4 February (2021)

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See detailDetection and Characterization of Circular Expanding UV Emissions Observed in Jupiter's Polar Auroral Regions
Hue, V.; Greathouse, T. K.; Gladstone, G. R. et al

in Journal of Geophysical Research. Space Physics (2021), 126(3), 28971

Jupiter's polar auroral region hosts UV auroral emissions that relate to the magnetospheric dynamics from the outer magnetosphere. Juno UVS has discovered intriguing features characterized by expanding ... [more ▼]

Jupiter's polar auroral region hosts UV auroral emissions that relate to the magnetospheric dynamics from the outer magnetosphere. Juno UVS has discovered intriguing features characterized by expanding emission circles of UV brightness <140 kR. These events are located at the border of the previously defined swirl region, nearby the polar dark region. The features expand into a circular shape up to ∼1,000 km in radius, at expansion velocities from 3.3 ± 1.7 up to 7.7 ± 3.5 km/s, as measured over the four best observed cases. Using color ratio measurements as a proxy for the depth of the recorded features, the mean electron energy responsible for these emissions is 80-160 keV. Events occurring in the outer magnetosphere at distances >100 RJ are likely causing for these features. Dayside magnetopause reconnection and Kelvin Helmholtz instabilities resulting from the shear flows near the magnetopause are expected to generate field aligned currents that could potentially be the cause of these features. [less ▲]

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See detailObservations of Jupiter’s Hydrogen Airglow by Juno’s UVS
Gómez, D.W.; Gladstone, G.R.; Greathouse, T.K. et al

Conference (2020, December)

While the primary function of the Juno spacecraft’s Ultraviolet Spectrograph (UVS) during perijove is to observe Jupiter’s auroral features, it is also capable of detecting and measuring Jupiter’s airglow ... [more ▼]

While the primary function of the Juno spacecraft’s Ultraviolet Spectrograph (UVS) during perijove is to observe Jupiter’s auroral features, it is also capable of detecting and measuring Jupiter’s airglow. The perijove location of Juno in Jupiter’s upper atmosphere allows for the UVS to detect Hydrogen Lyman-alpha and H2 emissions as a function of zenith angle. We look at the features of Jupiter’s airglow beginning early in the mission to attempt to determine trends based on a variety of criteria, including spacecraft latitude and local time information, solar zenith angle, and the location of the emissions themselves. Juno-UVS is also well suited to search for “shuttle glow” as the spacecraft moves through Jupiter’s atmosphere. “Shuttle glow” has been observed at Earth as a result of a spacecraft re-entering or orbiting at low altitude within an atmosphere. We will describe attempts to detect and characterize these photon emissions with Juno, which moves through Jupiter’s upper atmosphere at ~60 km/s. [less ▲]

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See detailTransient Luminous Events observed in Jupiter's upper atmosphere
Giles, R.; Greathouse, T.K.; Bonfond, Bertrand ULiege et al

Conference (2020, December)

The Ultraviolet Spectrograph (UVS) is a long-slit imaging spectrograph on the Juno mission, which has been in orbit around Jupiter since July 2016. UVS covers the 68-210 nm wavelength range with a ... [more ▼]

The Ultraviolet Spectrograph (UVS) is a long-slit imaging spectrograph on the Juno mission, which has been in orbit around Jupiter since July 2016. UVS covers the 68-210 nm wavelength range with a spectral resolution of 1.3-3.0 nm, and makes use of the spacecraft’s rotation to build up an ultraviolet image as the instrument slit sweeps across the planet. The primary purpose of UVS is to map Jupiter’s far-UV auroral emissions, but the instrument has also detected seven transient bright flashes, which we suggest may be Transient Luminous Events in Jupiter’s upper atmosphere. These bright flashes are only observed in a single spin of the spacecraft and their brightness decays exponentially with time, with a duration of ~1.6 ms. Their spectra are dominated by H2 Lyman band emission and based on the level of atmospheric absorption, we estimate a source altitude of 250 km above the 1-bar level. As seen by UVS, the emission regions are point sources, with maximum widths of 600-1800 km. These properties are consistent with the predicted properties of Sprites or Elves in Jupiter’s atmosphere (Yair et al., 2009, doi: 10.1029/2008JE003311, Luque et al., 2014, doi: 10.1002/2014JA020457). While tropospheric lightning has been frequently observed in Jupiter’s atmosphere, including by several other instruments on the Juno mission, Transient Luminous Events have not previously been observed in a planet other than Earth. [less ▲]

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See detailAurora to Magnetodisk Mapping: Connecting UV Emissions to Events in Jupiter’s Magnetosphere
Greathouse, T.K.; Gladstone, G.R.; Vogt, M.F. et al

Conference (2020, December)

The Juno Mission carries with it an ultraviolet spectrograph, Juno UVS, meant to map out Jupiter’s auroral emissions from an unprecedented vantage point above Jupiter’s poles. With views of the aurora at ... [more ▼]

The Juno Mission carries with it an ultraviolet spectrograph, Juno UVS, meant to map out Jupiter’s auroral emissions from an unprecedented vantage point above Jupiter’s poles. With views of the aurora at all local times, Juno UVS allows for the first comprehensive compilation of the local time variations of the auroral emissions. Using the Vogt et al. (2011, JGR 116, A03220; 2015, JGR 120, 2584-2599) magnetic flux mapping approach we invert the observed auroral emission maps into maps of those emissions in magnetodisk coordinates. In this way, we are able to reconstruct the approximate (depending on the accuracy of the Vogt mapping and JRM09 magnetic field model) structure and evolution of the source regions causing the auroral emissions leading to further insight on the dynamics of the middle to outer magnetosphere. We present mission average disk projected maps, those from assorted perijoves (close flyby of Jupiter by Juno on its highly elliptical orbit of ~53 days), and discuss their temporal evolution over timescales of minutes and hours (a single perijove) to months and years (perijove to perijove). [less ▲]

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See detailJovian auroral conductance from Juno-UVS: hemispheric asymmetry?
Gérard, Jean-Claude ULiege; Gkouvelis, Leonardos ULiege; Bonfond, Bertrand ULiege et al

Conference (2020, October 30)

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 ... [more ▼]

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. [less ▲]

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See detailA PRELIMINARY STUDY OF MIT COUPLING AT JUPITER BASED ON JUNO OBSERVATIONS AND MODELLING TOOLS
Blanc, Michel; Wang, Y.; André, Nicolas et al

Conference (2020, October 06)

The dynamics of the Jovian magnetosphere is controlled by the complex in- terplay of the planet’s fast rotation, its solar-wind interaction and its main plasma source at the Io torus. Juno observations ... [more ▼]

The dynamics of the Jovian magnetosphere is controlled by the complex in- terplay of the planet’s fast rotation, its solar-wind interaction and its main plasma source at the Io torus. Juno observations have amply demonstrated that the Magnetosphere-Ionosphere-Thermosphere (MIT) coupling process- es and regimes which control this interplay are significantly different from their Earth and Saturn counterparts. At the ionospheric level, these MIT cou- pling processes can be characterized by a set of key parameters which in- clude ionospheric electrodynamic parameters (conductances, currents and electric fields), exchanges of particles along field lines and auroral emissions. Knowledge of these key parameters in turn makes it possible to estimate the net deposition/extraction of momentum and energy into/out of the Jovian upper atmosphere. We will present a method combining Juno multi-instru- ment data (MAG, JADE, JEDI, UVS, JIRAM and WAVES), adequate modelling tools (the TRANSPLANET ionospheric dynamics model and a simplified set of ionospheric current closure equations) and the AMDA data handling tools to provide preliminary estimates of these key parameters and their variation along the ionospheric footprint of Juno’s magnetic field line and across the auroral ovals for three of the first perijoves of the mission. We will discuss how this synergistic use of data and models can also contribute to provide a better determination of poorly known parameters such as the vertical struc- ture of the auroral and polar Jovian neutral atmosphere. [less ▲]

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See detailA preliminary study of Magnetosphere-Ionosphere-Thermosphere coupling key parameters at Jupiter Based on Juno multi-instrument data and modelling tools
Blanc, M.; Wang, Y.; André, N. et al

Conference (2020, September 30)

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 ... [more ▼]

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. [less ▲]

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