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See detailMorphology of the UV aurorae Jupiter during Juno’s first perijove observations
Bonfond, Bertrand ULiege; Gladstone, G. R.; Grodent, Denis ULiege et al

in Geophysical Research Letters (2017)

On 27 August 2016, the NASA Juno spacecraft performed its first close-up observations of Jupiter during its perijove. Here we present the UV images and color ratio maps from the Juno-ultraviolet ... [more ▼]

On 27 August 2016, the NASA Juno spacecraft performed its first close-up observations of Jupiter during its perijove. Here we present the UV images and color ratio maps from the Juno-ultraviolet spectrometer UV imaging spectrograph acquired at that time. Data were acquired during four sequences (three in the north, one in the south) from 5:00 UT to 13:00 UT. From these observations, we produced complete maps of the Jovian aurorae, including the nightside. The sequence shows the development of intense outer emission outside the main oval, first in a localized region (255 ∘ –295 ∘ System III longitude) and then all around the pole, followed by a large nightside protrusion of auroral emissions from the main emission into the polar region. Some localized features show signs of differential drift with energy, typical of plasma injections in the middle magnetosphere. Finally, the color-ratio map in the north shows a well-defined area in the polar region possibly linked to the polar cap. [less ▲]

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See detailTransient brightening of Jupiter’s aurora observed by the Hisaki satellite and Hubble Space Telescope during approach phase of the Juno spacecraft
Kimura, Tomoki; Nichols, J.D.; Gray, R.L. et al

in Geophysical Research Letters (2017), 44

In early 2014, continuous monitoring with the Hisaki satellite discovered transient auroral emission at Jupiter during a period when the solar wind was relatively quiet for a few days. Simultaneous ... [more ▼]

In early 2014, continuous monitoring with the Hisaki satellite discovered transient auroral emission at Jupiter during a period when the solar wind was relatively quiet for a few days. Simultaneous imaging made by the Hubble Space Telescope (HST) suggested that the transient aurora is associated with a global magnetospheric disturbance that spans from the inner to outer magnetosphere. However, the temporal and spatial evolutions of the magnetospheric disturbance were not resolved because of the lack of continuous monitoring of the transient aurora simultaneously with the imaging. Here we report the coordinated observation of the aurora and plasma torus made by Hisaki and HST during the approach phase of the Juno spacecraft in mid‐2016. On day 142, Hisaki detected a transient aurora with a maximum total H2 emission power of ~8.5 TW. The simultaneous HST imaging was indicative of a large “dawn storm,” which is associated with tail reconnection, at the onset of the transient aurora. The outer emission, which is associated with hot plasma injection in the inner magnetosphere, followed the dawn storm within less than two Jupiter rotations. The monitoring of the torus with Hisaki indicated that the hot plasma population increased in the torus during the transient aurora. These results imply that the magnetospheric disturbance is initiated via the tail reconnection and rapidly expands toward the inner magnetosphere, followed by the hot plasma injection reaching the plasma torus. This corresponds to the radially inward transport of the plasma and/or energy from the outer to the inner magnetosphere. [less ▲]

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See detailMartian mesospheric cloud observations by IUVS on MAVEN: Thermal tides coupled to the upper atmosphere
Stevens; Siskind; Evans et al

in Geophysical Research Letters (2017), 44

The manuscript describes the observation of Martian mesosphericclouds between 60 and 80 km altitude by the Imaging Ultraviolet Spectrograph (IUVS) on NASA’sMAVEN spacecraft. The cloud observations are ... [more ▼]

The manuscript describes the observation of Martian mesosphericclouds between 60 and 80 km altitude by the Imaging Ultraviolet Spectrograph (IUVS) on NASA’sMAVEN spacecraft. The cloud observations are uniquely obtained at early morning local times, whichcomplement previous observations obtained primarily later in the diurnal cycle. Differences in thegeographic distribution of the clouds from IUVS observations indicate that the local time is crucial for theinterpretation of mesospheric cloud formation. We also report concurrent observations of upperatmospheric scale heights near 170 km altitude, which are diagnostic of temperature. These observationssuggest that the dynamics enabling the formation of mesospheric clouds propagate all the way to theupper atmosphere. [less ▲]

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See detailThe recent warming trend in North Greenland
Orsi, A.; Kawamura, K.; Masson-Delmotte, V. et al

in Geophysical Research Letters (2017)

The Arctic is among the fastest warming regions on Earth, but it is also one with limited spatial coverage of multi-decadal instrumental surface air temperature measurements. Consequently, atmospheric ... [more ▼]

The Arctic is among the fastest warming regions on Earth, but it is also one with limited spatial coverage of multi-decadal instrumental surface air temperature measurements. Consequently, atmospheric reanalyses are relatively unconstrained in this region, resulting in a large spread of estimated 30-year recent warming trends, which limits their use to investigate the mechanisms responsible for this trend. Here, we present a surface temperature reconstruction over 1982-2011 at NEEM (51∘ W, 77∘ N), in North Greenland, based on the inversion of borehole temperature and inert gas isotope data. We find that NEEM has warmed by 2.7±0.33∘C over the past 30 years, from the long-term 1900-1970 average of -28.55±0.29∘C. The warming trend is principally caused by an increase in downward longwave heat flux. Atmospheric reanalyses underestimate this trend by 17%, underlining the need for more in situ observations to validate reanalyses. [less ▲]

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See detailInfrared observations of Jovian aurora from Juno's first orbits: Main oval and satellite footprints
Mura, A.; Adriani, A.; Altieri, F. et al

in Geophysical Research Letters (2017), 44(11), 5308-5316

The Jovian Infrared Auroral Mapper (JIRAM) is an imager/spectrometer on board NASA/Juno mission for the study of the Jovian aurorae. The first results of JIRAM's imager channel observations of the H3 ... [more ▼]

The Jovian Infrared Auroral Mapper (JIRAM) is an imager/spectrometer on board NASA/Juno mission for the study of the Jovian aurorae. The first results of JIRAM's imager channel observations of the H3 + infrared emission, collected around the first Juno perijove, provide excellent spatial and temporal distribution of the Jovian aurorae, and show the morphology of the main ovals, the polar regions, and the footprints of Io, Europa and Ganymede. The extended Io “tail” persists for ~3 h after the passage of the satellite flux tube. Multi-arc structures of varied spatial extent appear in both main auroral ovals. Inside the main ovals, intense, localized emissions are observed. In the southern aurora, an evident circular region of strong depletion of H3 + emissions is partially surrounded by an intense emission arc. The southern aurora is brighter than the north one in these observations. Similar, probably conjugate emission patterns are distinguishable in both polar regions. ©2017. American Geophysical Union. All Rights Reserved. [less ▲]

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See detailPreliminary JIRAM results from Juno polar observations: 3. Evidence of diffuse methane presence in the Jupiter auroral regions
Moriconi, M. L.; Adriani, A.; Dinelli, B. M. et al

in Geophysical Research Letters (2017), 44(10), 4641-4648

Throughout the first orbit of the NASA Juno mission around Jupiter, the Jupiter InfraRed Auroral Mapper (JIRAM) targeted the northern and southern polar regions several times. The analyses of the acquired ... [more ▼]

Throughout the first orbit of the NASA Juno mission around Jupiter, the Jupiter InfraRed Auroral Mapper (JIRAM) targeted the northern and southern polar regions several times. The analyses of the acquired images and spectra confirmed a significant presence of methane (CH4) near both poles through its 3.3 μm emission overlapping the H3 + auroral feature at 3.31 μm. Neither acetylene (C2H2) nor ethane (C2H6) have been observed so far. The analysis method, developed for the retrieval of H3 + temperature and abundances and applied to the JIRAM-measured spectra, has enabled an estimate of the effective temperature for methane peak emission and the distribution of its spectral contribution in the polar regions. The enhanced methane inside the auroral oval regions in the two hemispheres at different longitude suggests an excitation mechanism driven by energized particle precipitation from the magnetosphere. ©2017. American Geophysical Union. All Rights Reserved. [less ▲]

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See detailPreliminary JIRAM results from Juno polar observations: 1. Methodology and analysis applied to the Jovian northern polar region
Dinelli, B. M.; Fabiano, F.; Adriani, A. et al

in Geophysical Research Letters (2017), 44(10), 4625-4632

During the first orbit around Jupiter of the NASA/Juno mission, the Jovian Auroral Infrared Mapper (JIRAM) instrument observed the auroral regions with a large number of measurements. The measured spectra ... [more ▼]

During the first orbit around Jupiter of the NASA/Juno mission, the Jovian Auroral Infrared Mapper (JIRAM) instrument observed the auroral regions with a large number of measurements. The measured spectra show both the emission of the H3+ ion and of methane in the 3–4 μm spectral region. In this paper we describe the analysis method developed to retrieve temperature and column density (CD) of the H3+ ion from JIRAM spectra in the northern auroral region. The high spatial resolution of JIRAM shows an asymmetric aurora, with CD and temperature ovals not superimposed and not exactly located where models and previous observations suggested. On the main oval averaged H3+ CDs span between 1.8 × 1012 cm−2 and 2.8 × 1012 cm−2, while the retrieved temperatures show values between 800 and 950 K. JIRAM indicates a complex relationship among H3+ CDs and temperatures on the Jupiter northern aurora. ©2017. American Geophysical Union. All Rights Reserved. [less ▲]

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See detailPreliminary JIRAM results from Juno polar observations: 2. Analysis of the Jupiter southern H3 + emissions and comparison with the north aurora
Adriani, Alberto; Mura, Alessandro; Moriconi, M. L. et al

in Geophysical Research Letters (2017), 44(10), 4633-4640

The Jupiter InfraRed Auroral Mapper (JIRAM) aboard Juno observed the Jovian South Pole aurora during the first orbit of the mission. H3 + (trihydrogen cation) and CH4 (methane) emissions have been ... [more ▼]

The Jupiter InfraRed Auroral Mapper (JIRAM) aboard Juno observed the Jovian South Pole aurora during the first orbit of the mission. H3 + (trihydrogen cation) and CH4 (methane) emissions have been identified and measured. The observations have been carried out in nadir and slant viewing both by a L-filtered imager and a 2–5 μm spectrometer. Results from the spectral analysis of the all observations taken over the South Pole by the instrument are reported. The coverage of the southern aurora during these measurements has been partial, but sufficient to determine different regions of temperature and abundance of the H3 + ion from its emission lines in the 3–4 μm wavelength range. Finally, the results from the southern aurora are also compared with those from the northern ones from the data taken during the same perijove pass and reported by Dinelli et al. (2017). ©2017. American Geophysical Union. All Rights Reserved. [less ▲]

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See detailResponse of Jupiter's auroras to conditions in the interplanetary medium as measured by the Hubble Space Telescope and Juno
Nichols, J. D.; Badman, S. V.; Bagenal, F. et al

in Geophysical Research Letters (2017)

We present the first comparison of Jupiter's auroral morphology with an extended, continuous and complete set of near-Jupiter interplanetary data, revealing the response of Jupiter's auroras to the ... [more ▼]

We present the first comparison of Jupiter's auroral morphology with an extended, continuous and complete set of near-Jupiter interplanetary data, revealing the response of Jupiter's auroras to the interplanetary conditions. We show that for ∼1-3 days following compression region onset the planet's main emission brightened. A duskside poleward region also brightened during compressions, as well as during shallow rarefaction conditions at the start of the program. The power emitted from the noon active region did not exhibit dependence on any interplanetary parameter, though the morphology typically differed between rarefactions and compressions. The auroras equatorward of the main emission brightened over ∼10 days following an interval of increased volcanic activity on Io. These results show that the dependence of Jupiter's magnetosphere and auroras on the interplanetary conditions are more diverse than previously thought. [less ▲]

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See detailJuno-UVS Approach Observations of Jupiter's Auroras
Gladstone, G. R.; Versteeg, M. H.; Greathouse, T. K. et al

in Geophysical Research Letters (2017)

Juno-UVS observations of Jupiter's aurora obtained during approach are presented. Prior to the bow-shock crossing on 24 June 2016, the Juno approach provided a rare opportunity to correlate local solar ... [more ▼]

Juno-UVS observations of Jupiter's aurora obtained during approach are presented. Prior to the bow-shock crossing on 24 June 2016, the Juno approach provided a rare opportunity to correlate local solar wind conditions with Jovian auroral emissions. Some of Jupiter's auroral emissions are expected to be controlled or modified by local solar wind conditions. Here we compare synoptic Juno-UVS observations of Jupiter's auroral emissions, acquired during 3-29 June 2016, with in situ solar wind observations, and related Jupiter observations from Earth. Four large auroral brightening events are evident in the synoptic data, in which the total emitted auroral power increases by a factor of 3-4 for a few hours. Only one of these brightening events correlates well with large transient increases in solar wind ram pressure. The brightening events which are not associated with the solar wind generally have a rise time of ~2 hours and a decay time of ~5 hours. [less ▲]

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See detailDynamics of the flares in the active polar region of Jupiter
Bonfond, Bertrand ULiege; Grodent, Denis ULiege; Badman, S. V. et al

in Geophysical Research Letters (2016)

The dusk-side of the polar region of Jupiter's UV aurorae, called the active region, sometimes exhibits quasi-periodic (QP) flares on time-scales of 2-3 minutes. Based on Hubble Space Telescope Far-UV ... [more ▼]

The dusk-side of the polar region of Jupiter's UV aurorae, called the active region, sometimes exhibits quasi-periodic (QP) flares on time-scales of 2-3 minutes. Based on Hubble Space Telescope Far-UV time-tag images, we show for the first time that the northern hemisphere also displays QP-flares. The area covered by these flares can reach up to 2.4 × 108 km2 (i.e. the whole active region), but often only involves an area an order of magnitude smaller. Using a magnetic field mapping model, we deduced that these areas correspond to the dayside outer magnetosphere. In our dataset, quasi-periodic features are only seen on half of the cases and even on a given observation, a region can be quiet for one half and blinking on the other half. Consecutive observations in the two hemispheres show that the brightening can occur in phase. Combined with the size and location of the flares, this behaviour suggests that the QP-flares most likely take place on closed magnetic field lines. [less ▲]

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See detailDirect measurement of evapotranspiration from a forest using a superconducting gravimeter
Van Camp, Michel; de Viron, Olivier; Pajot-Métivier, Gwendoline et al

in Geophysical Research Letters (2016), 43

Evapotranspiration (ET) controls the flux between the land surface and the atmosphere. Assessing the ET ecosystems remains a key challenge in hydrology. We have found that the ET water mass loss can be ... [more ▼]

Evapotranspiration (ET) controls the flux between the land surface and the atmosphere. Assessing the ET ecosystems remains a key challenge in hydrology. We have found that the ET water mass loss can be directly inferred from continuous gravity measurements: as water evaporates and transpires from terrestrial ecosystems, the mass distribution of water decreases, changing the gravity field. Using continuous superconducting gravity measurements, we were able to identify daily gravity changes at the level of, or smaller than, 10-9 nms-2 (or 10-10 g) per day. This corresponds to 1.7mmof water over an area of 50 ha. The strength of this method is its ability to enable a direct, traceable and continuous monitoring of actual ET for years at the mesoscale with a high accuracy. [less ▲]

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See detailWeakening of Jupiter's main auroral emission during January 2014
Badman, S. V.; Bonfond, Bertrand ULiege; Fujimoto, M. et al

in Geophysical Research Letters (2016), 43(3), 988-997

In January 2014 Jupiter's FUV main auroral oval decreased its emitted power by 70% and shifted equatorward by ∼1°. Intense, low-latitude features were also detected. The decrease in emitted power is ... [more ▼]

In January 2014 Jupiter's FUV main auroral oval decreased its emitted power by 70% and shifted equatorward by ∼1°. Intense, low-latitude features were also detected. The decrease in emitted power is attributed to a decrease in auroral current density rather than electron energy. This could be caused by a decrease in the source electron density, an order of magnitude increase in the source electron thermal energy, or a combination of these. Both can be explained either by expansion of the magnetosphere or by an increase in the inward transport of hot plasma through the middle magnetosphere and its interchange with cold flux tubes moving outward. In the latter case the hot plasma could have increased the electron temperature in the source region and produced the intense, low-latitude features, while the increased cold plasma transport rate produced the shift of the main oval. © 2016. The Authors. [less ▲]

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See detailVolcanic eruptions boost tropical Pacific biological productivity
Chikamoto, Megumi O.; Timmermann, Axel; Yoshimori, Masakazu et al

in Geophysical Research Letters (2016), 43

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See detailPositive trends in Southern Hemisphere carbonyl sulfide
Kremser, Stefanie; Jones, Nicholas B.; Palm, Mathias et al

in Geophysical Research Letters (2015), 42

Transport of carbonyl sulfide (OCS) from the troposphere to the stratosphere contributes sulfur to the stratospheric aerosol layer, which reflects incoming short-wave solar radiation, cooling the climate ... [more ▼]

Transport of carbonyl sulfide (OCS) from the troposphere to the stratosphere contributes sulfur to the stratospheric aerosol layer, which reflects incoming short-wave solar radiation, cooling the climate system. Previous analyses of OCS observations have shown no significant trend, suggesting that OCS is unlikely to be a major contributor to the reported increases in stratospheric aerosol loading and indicating a balanced OCS budget. Here we present analyses of ground-based Fourier transform spectrometer measurements of OCS at three Southern Hemisphere sites spanning 34.45°S to 77.80°S. At all three sites statistically significant positive trends are seen from 2001 to 2014 with an observed overall trend in total column OCS at Wollongong of 0.73 ± 0.03%/yr, at Lauder of 0.43 ± 0.02%/yr, and at Arrival Heights of 0.45 ± 0.05%/yr. These observed trends in OCS imply that the OCS budget is not balanced and could contribute to constraints on current estimates of sources and sinks. [less ▲]

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See detailMAVEN IUVS observations of the aftermath of the Comet Siding Spring meteor shower on Mars
Schneider, Nick; Deighan, Justin; Stewart, Ian et al

in Geophysical Research Letters (2015)

We report the detection of intense emission from magnesium and iron in Mars' atmosphere caused by a meteor shower following Comet Siding Spring's close encounter with Mars. The observations were made with ... [more ▼]

We report the detection of intense emission from magnesium and iron in Mars' atmosphere caused by a meteor shower following Comet Siding Spring's close encounter with Mars. The observations were made with the Imaging Ultraviolet Spectrograph, a remote sensing instrument on the Mars Atmosphere and Volatile EvolutioN spacecraft orbiting Mars. Ionized magnesium caused the brightest emission from the planet's atmosphere for many hours, resulting from resonant scattering of solar ultraviolet light. Modeling suggests a substantial fluence of low-density dust particles 1–100 µm in size, with the large amount and small size contrary to predictions. The event created a temporary planet-wide ionospheric layer below Mars' main dayside ionosphere. The dramatic meteor shower response at Mars is starkly different from the case at Earth, where a steady state metal layer is always observable but perturbations caused by even the strongest meteor showers are challenging to detect. [less ▲]

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See detailTerrestrial OH nightglow measurements during the Rosetta flyby
Migliorini, A.; Gérard, Jean-Claude ULiege; Soret, Lauriane ULiege et al

in Geophysical Research Letters (2015), 42

We present a study of the terrestrial hydroxyl nightglow emissions observed with the Visible and Infrared Thermal Imaging Spectrometer on board the Rosetta mission. During these observations, the OH Δv  ... [more ▼]

We present a study of the terrestrial hydroxyl nightglow emissions observed with the Visible and Infrared Thermal Imaging Spectrometer on board the Rosetta mission. During these observations, the OH Δv = 1 and 2 sequences were measured simultaneously. This allowed investigating the relative population of the v = 1 to 9 vibrational levels by using both sequences. In particular, the relative population of the vibrational level v = 1 is determined for the first time from observations. The vibrational population decreases with increasing vibrational quantum number. A good agreement is found with a recent model calculation assuming multiquantum relaxation for OH(v) quenching by O2 and single-quantum relaxation for OH(v) by N2. [less ▲]

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See detailTransient internally driven aurora at Jupiter discovered by Hisaki and the Hubble Space Telescope
Kimura, Tomoki; Badman, Sarah; Tao, Chihiro et al

in Geophysical Research Letters (2015), 42

Jupiter’s auroral emissions reveal energy transport and dissipation through the planet’s giant magnetosphere. While the main auroral emission is internally driven by planetary rotation in the steady state ... [more ▼]

Jupiter’s auroral emissions reveal energy transport and dissipation through the planet’s giant magnetosphere. While the main auroral emission is internally driven by planetary rotation in the steady state, transient brightenings are generally thought to be triggered by compression by the external solar wind. Here we present evidence provided by the new Hisaki spacecraft and the Hubble Space Telescope that shows that such brightening of Jupiter’s aurora can in fact be internally driven. The brightening has an excess power up to ~550 GW. Intense emission appears from the polar cap region down to latitudes around Io’s footprint aurora, suggesting a rapid energy input into the polar region by the internal plasma circulation process. [less ▲]

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See detailTen years of Martian nitric oxide nightglow observations
Stiepen, Arnaud ULiege; Gérard, Jean-Claude ULiege; Gagné, Marie-Eve et al

in Geophysical Research Letters (2015)

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See detailNew observations of molecular nitrogen in the Martian upper atmosphere by IUVS on MAVEN
Stevens, M. H.; Evans, J. S.; Schneider, N. M. et al

in Geophysical Research Letters (2015)

We identify molecular nitrogen (N2) emissions in the Martian upper atmosphere using the Imaging Ultraviolet Spectrograph (IUVS) on NASA's Mars Atmosphere and Volatile EvolutioN (MAVEN) mission. We report ... [more ▼]

We identify molecular nitrogen (N2) emissions in the Martian upper atmosphere using the Imaging Ultraviolet Spectrograph (IUVS) on NASA's Mars Atmosphere and Volatile EvolutioN (MAVEN) mission. We report the first observations of the N2 Lyman-Birge-Hopfield (LBH) bands at Mars and confirm the tentative identification of the N2 Vegard-Kaplan (VK) bands. We retrieve N2 density profiles from the VK limb emissions and compare calculated limb radiances between 90 and 210km against both observations and predictions from a Mars general circulation model (GCM). Contrary to earlier analyses using other satellite data, we find that N2 abundances exceed GCM results by about a factor of 2 at 130km but are in agreement at 150km. The analysis and interpretation are enabled by a linear regression method used to extract components of UV spectra from IUVS limb observations. © 2015. American Geophysical Union. All Rights Reserved. [less ▲]

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