Recent Juno-UVS Observations of Jupiter’s Auroras Randy Gladstone (1,2), Thomas Greathouse (1), Maarten Versteeg (1), Vincent Hue (1), Joshua Kammer (1), Michael Davis (1), Jean-Claude Gérard (3), Denis Grodent (3), Bertrand Bonfond (3), Frederic Allegrini (1,2), Robert Ebert (1,2), Barry Mauk (4), Fran Bagenal (8), Scott Bolton (1) , Steven Levin (5) , and John Connerney (6,7)
Moscone West - 2009
The Juno mission offers the opportunity to study Jupiter, from its inner structure, up to its magnetospheric
environment. Juno was launched on August 2011 and its Jupiter orbit insertion (JOI) occurred on July 4 2016. The nominal Juno mission involves 35 science polar-orbits of 14-days period, with perijove and apojove distances located at 0.06 Rj and 45 Rj, respectively. Juno-UVS is a UV spectrograph with a bandpass of 70<λ<205 nm, designed to characterize Jupiter UV emissions. One of the main additions of UVS compared to its predecessors (New Horizons- and Rosetta- Alice, LRO-LAMP) is a 2.54 mm tantalum shielding, to protect it from the harsh radiation environment at Jupiter, and a scan mirror, to allow for targeting specific auroral and atmospheric features at +/- 30˚ perpendicular to the Juno spin plane. It will provide new constraints on Jupiter’s auroral morphology, spectral features, and vertical structure, while providing remote-sensing constraints for the onboard waves and particle instruments. It will also be used to probe upper-atmospheric composition through absorption features found in the UV spectra using reflected solar UV radiation. For example, stratospheric hydrocarbons such as C H and C H are known to absorb significantly in the 150-180 nm regions, and these absorption features can be used to determine their abundances. We will present our search for the spectroscopic features seen in Jupiter’s reflected sunlight during the first perijove.
The characteristics of the bar code events resemble those of the relativistic electron microburst events observed at Earth, both with regard to the energies involved (a few megaelectron volts) and to the typi- cal timescales (less than 1 s; Imhof & Nightingale, 1992). The microburst events have been associated with large-amplitude oblique whistler waves in the radiation belt (Cattell et al., 2008; Kersten et al., 2011). Simula- tions carried out for the Earth case show that such large-amplitude oblique whistler waves are able to transfer up to 4 MeV to the electrons within tens of milliseconds and to considerably modify the pitch angle of the electrons (Cattell et al., 2008; Omura et al., 2007). Thus, the terrestrial microburst events could be caused by oblique whistler waves in the radiation belts either impulsively accelerating electrons up to energies of a few megaelectron volts or scattering relativistic electrons into the loss cone, which requires a preexisting reservoir of relativistic particles, or both (Breneman et al., 2017; Kersten et al., 2011). However, at Jupiter, the observed relativistic electrons originate from the polar regions rather than the radiation belts or the plasma sheet. Thus, the existence of such a reservoir is excluded. Only a mechanism involving local acceleration of electrons close (less than 1 R J ) to the planet could explain the Juno-UVS bar code events reported here. For example, these events could be related to the high-energy tail of the electron distribution associated with the interaction between upgoing electrons and upgoing whistler waves described by Elliott et al. (2018). Future comparisons with observations from the other instruments on board Juno will allow us to test this scenario.
Our method is based on the use of Juno ‐UVS multispectral images of auroral and polar emissions. Juno‐UVS (Gladstone et al., 2017) is an ultraviolet imaging spectrograph operating in the 68 to 210 nm range including the H 2 Werner and Lyman bands emissions. The “dog bone” entrance slit is made of three segments with
ﬁelds of view of 0.2° × 2.5°, 0.025° × 2.0°, and 0.2° × 2.5°. Global images of both polar regions are reconstructed by taking advantage of the spacecraft rotation, as the ﬁeld of view sweeps across the planet at each rotation. Using a neutral atmosphere model and an electron transport code, it is possible to retrieve characteristics of the precipitating electron populations from the observation of the photons they produce. The precipitated energy ﬂux reaching the atmosphere is obtained from the integration of the unabsorbed H 2
2. Instruments and Observation Modes
Juno is a spin ‐stabilized spacecraft that has been orbiting Jupiter since 5 July 2016 on a high elliptical 53.5‐ day polar orbit (Bolton et al., 2017). The Juno ‐UVS instrument is a photon‐counting imaging spectrograph with a passband extending from 70 to 205 nm (Gladstone et al., 2017). This spectral range includes part of the H 2 Lyman and Werner bands and the HI Lyman ‐α line. It is equipped with a scan mirror that allows it to look up to ±30° perpendicular to the Juno spin plane. The long axis of the slit is parallel to the spin axis. The “dog bone”‐shaped slit is made of three segments with ﬁelds of view of 0.2° × 2.5°, 0.025° × 2.0° and 0.2° × 2.5°. The point spread function corresponds to about three detector pixels. For a distance of 1 R J above the aurora, the spatial resolution on the aurora is ~250 km perpendicular to the slit axis and 150 km (3 pixels) along the slit. The spectral resolution of the ﬁlled slit segments is 2.2 and 1.3 nm, respectively (Greathouse et al., 2013). Individual photon events are recorded by their wavelength and location along the slit on the detector as the spacecraft spins at a rate of 2 rpm. Images can then be reconstructed by taking advantage of the motion of the ﬁeld of view across the planet and the orientation of the scan mirror. As the spacecraft spins, if observed during the swath, a given point on the planet is seen during 0.017 s in the wide section of the slit. The combination of these successive stripes obtained every 30 s produces composite images of all or part of the polar regions, depending on the orbital con ﬁguration. These images are then projected on ortho- graphic maps to generate polar views of the aurora. In the ﬁgures presented in this study, the selected alti- tude is 400 km above the 1 ‐bar level (Bonfond et al., 2015). The spatial resolution in kilometers on the composite maps depends on different factors. It is inversely proportional to the distance from the
and to reflected sunlight. While there is overlap between the two sources, their contributions are expected to be easily separable.
During commissioning, yearly cruise calibrations, and at the apojoves of each Jupiter orbit, standard UV-bright stars will be observed to determine and monitor the effective area of Juno-UVS. These stellar sources will also be observed at various positions along the slit to provide accurate slit dimensions, vignetting information, and row-to-row variations in detector sensitivity. Filled-slit line shapes are acquired by looking at the interplanetary Lyα signal (e.g., Pryor et al. 2008). Juno-UVS “first-light” observations occurred during high- voltage checkout (HVCO), and are presented in Fig. 11. Also during high-voltage checkout, the optimal high voltage and discriminator settings are found, by inspection of a matrix of test observations and pulse height distributions (PHDs). The pulse height is obtained for every event, which makes monitoring PHDs much easier than in heritage versions of the Juno-UVS instrument.
CH 4 temperature in the south would then imply either higher emission altitudes or a warmer atmospheric
structure than in the north. The northern and southern methane enhancements appear located well inside the auroral ovals and in a narrow range of longitudes, although the limited coverage of the south pole prevents a de ﬁnite conclusion. If this pattern will be conﬁrmed from the next observations, it would suggest that the excitation leading to infrared emission is linked to magnetospheric phenomena and in particular to the auroral particle precipitation in the polar caps [Gladstone et al., 2002; Cravens et al., 2003; Hui et al., 2009; Ozak et al., 2013]. JIRAM measurements give us pictures in unprecedented detail of the methane enhance- ments in both of Jupiter ’s polar regions and may help in understanding the actual mechanism at work in the ion aurora. Finally, we hope that during the next JUNO orbits, further observations of the polar regions will support and improve the ﬁndings reported in this paper.
 . Quantitative deviations between the respective studies are due to a number of effects, which include updated oscillation parameter values, taking into account different oscillation baselines and background sources in the sim- ulation of JUNO, updated experimental layouts with non- parametric energy and zenith resolutions from detailed MC in the case of IceCube, as well as an extended set of systematic uncertainties in the combined analysis. Overall, the offset between the stand-alone experiments ’ Δm 2 31 minima in the wrong ordering remains large compared to the precision with which they constrain the parameter. Finally, we note that a combined measurement of the oscillation parameters of the PMNS paradigm  , such as sin 2 ðθ 13 Þ or Δm 2 31 , does not significantly improve the stand- alone capabilities or the measurements with the existing generation of experiments.
Figure 2 shows the pro ﬁles of the measured electron energy ﬂux as a func- tion of the characteristic energy for times when Juno crossed the low- altitude magnetic ﬁeld lines connecting to the main aurora (Northern and Southern Hemispheres). Collectively, the points represent measurements spanning perijove (PJ) 1 to PJ8. Note that JEDI ’s lower energy range for electrons is ~30 keV. The largest characteristic or peaked energies observed in the main aur- oral region are ~300 –400 keV, in agreement with those observed in previous case study event (Mauk et al., 2017b). The majority of the points cluster together and depict a nonlinear trend —a factor of 10 increase in characteristic energy produces roughly ~100 increase in energy ﬂux. In Figure 2b we distinguish the points associated with the broadband energy (no peak) distributions and those with peaked (nonmonotonic) distri- butions. Figures 2c and 2d color code the measurements by the Northern and Southern Hemispheres and the PJ number, respectively. An interesting pattern that emerges is the similar energy ﬂux relationship between both the broadband with no peak distributions and those that show a clear peak. For characteristic energies greater than ~100 keV the populations are clearly intermixed; however, there may be a difference below ~80 keV, but there is signi ﬁcant scatter in the energy ﬂux. Why or how do two seemingly distinct acceleration processes produce similar relationships? This is an unexpected result and we discuss it further in section 4. As mentioned previously, there are several types of energetic electron distributions associated with the main aurora. Previous publications have focused on two general types: broadband with no peak and the peaked distributions (Allegrini et al., 2017; Clark, Mauk, Paranicas, et al., 2017; Ebert et al., 2017; Mauk et al., 2017a, 2017b, 2018). Here we expand the list and show the various types of electron distributions (Figure 3) asso- ciated with the main auroral crossings. Figure 3 illustrates ﬁve types of energy spectra (intensity as a function of electron energy) with four qualitative differences. (1) The peaked energy distribution with a soft tail that drops off dramatically after the peak (Figure 3, purple curve). These sorts of distributions are thought to be associated with parallel potential structures in the auroral acceleration region (Clark, Mauk, Haggerty, et al., 2017; Mauk et al., 2017b). They almost always exhibit a plateau in differential intensity below the peak energy,
4.2 Ammonia and water
The depletion of ammonia to great depths measured by Juno MWR is reminiscent of a long-standing issue, that of Jupiter’s deep water abundance. Already in the 1980s, 5-µm spectroscopic observations of Jupiter’s atmosphere had revealed a very low abundance of water vapor, one to two orders of magnitude less than the solar value, down to at least 6 bars in a wide region covering −40 ◦ to +40 ◦ latitude, with three times lower abundance in Jupiter’s hot spots (Bjoraker et al., 1986). A simple explanation was proposed: Jupiter’s water clouds form narrow columns of humid air inside which water efficiently rains out to the cloud base, leaving the remaining region dry because of compensating subsidence (Lunine & Hunten, 1987). However this simple idea was shown to be incompatible with an Earth-based parametrization of cumulus clouds (del Genio & McGrattan, 1990), for at least two reasons. First, compensating subsidence stabilizes the atmosphere and prevents further cumulus cloud activity, and second, upward mixing tends to bring moisture up from the cloud base level which is itself soaked by rain reevaporation. The picture, further strengthened by later detailed microphysical models (Palotai & Dowling, 2008), held to this day. When the Galileo probe measured an extremely low abundance of water in a 5-µm hot spot (Niemann et al., 1998; Wong et al., 2004), the explanation was that this was a special region of Jupiter, mostly downwelling and consequently dry, due to global-scale wave activity (Ortiz et al., 1998; Showman & Ingersoll, 1998; Showman & Dowling, 2000; Friedson, 2005).
those identified as (1) above is that the apparent stochastic acceleration occurs primarily in the downward direction. 4) Finally, Juno sometimes observes strong downward ion inverted V’s indicating the existence of downward electric potentials up to sometimes greater than 400 kV. The surprise here is that there also occurs simultaneously the upward and downward broadband acceleration of electrons such that the associated auroral emissions would be as intense as those observed in other regions. In this presentation we explore the characteristics of, and the relationships between, these different regimes with a particular focus on the relationship between electrons and ions. One of the surprises is that: A) downward ion inverted-V distributions are quite common within the main aurora with angular characteristic that suggest that they are accelerated downward at positions that are large distances upward away from the spacecraft, while B) downward ion inverted-V’s have not been observed at radial positions greater than, say 4 RJ. This and other conundrums about the different auroral acceleration regimes are explored.
Les télomères sont des structures nucléoprotéiques spécialisées qui assurent la stabilité du génome en protégeant les extrémités chromosomiques. Afin d’empêcher des activités indésirables, la réparation des dommages à l’ADN doit être convenablement régulée au niveau des télomères. Pourtant, il existe peu d’études de la réparation des dommages induits par les ultraviolets (UVs) dans un contexte télomérique. Le mécanisme de réparation par excision de nucléotides (NER pour « Nucleotide Excision Repair ») permet d’éliminer les photoproduits. La NER est un mécanisme très bien conservé de la levure à l’humain. Elle est divisée en deux sous voies : une réparation globale du génome (GG-NER) et une réparation couplée à la transcription (TC-NER) plus rapide et plus efficace. Dans notre modèle d’étude, la levure Saccharomyces cerevisiae, une forme compactée de la chromatine nommée plus fréquemment « hétérochromatine » a été décrite. Cette structure particulière est présente entre autres, au niveau des régions sous- télomériques des extrémités chromosomiques. La formation de cette chromatine particulière implique quatre protéines nommées Sir (« Silent Information Regulator »). Elle présente différentes marques épigénétiques dont l’effet est de réprimer la transcription. L’accès aux dommages par la machinerie de réparation est-il limité par cette chromatine compacte ? Nous avons donc étudié la réparation des lésions induites par les UVs dans différentes régions associées aux télomères, en absence ou en présence de protéines Sir. Nos données ont démontré une modulation de la NER par la chromatine, dépendante des nucléosomes stabilisés par les Sir, dans les régions sous-télomériques. La NER était moins efficace dans les extrémités chromosomiques que dans les régions plus proches du centromère. Cet effet était dépendant du complexe YKu de la coiffe télomérique, mais pas dépendant des protéines Sir. La transcription télomériques pourrait aider la réparation des photoproduits, par l’intermédiaire de la sous-voie de TC-NER, prévenant ainsi la formation de mutations dans les extrémités chromosomiques. Des ARN non codants nommés TERRA sont produits mais leur rôle n’est pas encore clair. Par nos analyses, nous avons confirmé que la transcription des TERRA faciliterait la NER dans les différentes régions sous- télomériques.
This study focuses on the conditions and circumstances of the organization of distance learning (DL) offered by the Virtual University of Senegal (UVS), in an environment of developing countries in sub-Saharan Africa and in a scientific context that encourages the emergence of research exploring the reduction of distances in DL through proximity. Three specific objectives (SO) are targeted: on the one hand, to identify the factors of objective proximity, inherent to the design (SO 1.1) and implementation (SO 1.2) of the UVS pedagogical system; on the other hand, to identify the factors of subjective proximity, contained in the student experience (SO 2). Because of the complex interferences that the environment exerts on the conditions and circumstances in which training is organized, our analysis draws on the systemic approach to explore the components that would reveal the factors that promote proximity between the UVS pedagogical system and the learners. This also justifies the choice of the qualitative approach of studying three (3) case studies, taken as units of the institutional pedagogical system and selected at the end of a recruitment process based on a concern for variability. Offered in the first semester of their program, these courses belong to three different fields (technology, legal sciences and social sciences) and each involves three types of primary participants in our study (one teacher, one tutor and two students), in addition to the twenty or so secondary participants. The combination of this diversity of sources with a plurality of data collection and analysis tools constitutes the methodological base mobilized to achieve the rigor and scientificity required in a case study.
The minimum lifetime of this hot plasma feature is therefore ∼17 h, although the exact lifetime of this region of hot plasma may be significantly greater. Prior to the magnetopause crossing on DOY 196, there is no indication in JADE or JEDI data of the hot plasma beginning to dissipate, and the feature is not observed again when Juno re-enters the magnetosphere at 7:16 on DOY 197 (Hospodarsky et al., 2017 ), suggesting the true lifetime of this feature is between ∼17 and 27 h. MAG signatures also demonstrate significant dis- turbances in the magnetic field throughout this interval, consistent with a region of hot plasma. We note that these persistent hot plasma populations are primarily present at higher southern magnetic latitudes, extending to ∼30 R J below the current sheet. Reductions of the high energy populations during this inter- val only occur during current sheet encounters. During these current sheet approaches, the intensity flux drops by roughly an order of magnitude in the 50–200 keV energy range, and proton and ion pitch angle distributions simultaneously become increasingly field-aligned, suggesting the particle motions are primar- ily southward. Additionally, the auroral emissions observed with HST during this day (Figure 1d ), while enhanced compared to typical intensities, show attributes consistent with other HST orbits in this sequence with no clear remnant of the dawn storm remaining in the images.