247 results on '"P. Louarn"'
Search Results
2. Upgrading SPHERE with the second-stage adaptive optics system SAXO+: conceptual design of the opto-mechanical module
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Jackson, Kathryn J., Schmidt, Dirk, Vernet, Elise, Stadler, Eric, Schreiber, Laura, Cortecchia, Fausto, Lombini, Matteo, Diolaiti, Emiliano, Magnard, Yves, Rabou, Patrick, Rochat, Sylvain, De Rosa, Adriano, Malaguti, Giuseppe, Maurel, Didier, Morgante, Gianluca, Schiavone, Filomena, Terenzi, Luca, Chauvin, Gael, Ferreira, Florian, Gratton, Raffaele, Hubin, Norbert, Kasper, Markus, Langlois, Maud, Le Louarn, Miska, Loupias, Magali, Mazoyer, Johan, Milli, Julien, Mouillet, David, N’Diaye, Mamadou, Rousseau, Sylvain, Tallon, Michel, Vidal, Fabrice, Wildi, François, Zins, Gerard, and Boccaletti, Anthony
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- 2024
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3. Hierarchical Superhydrophobic Device to Concentrate and Precisely Localize Water-Soluble Analytes: A Route to Environmental Analysis.
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Fabre, Victor, Carcenac, Franck, Laborde, Adrian, Doucet, Jean-Baptiste, Vieu, Christophe, Louarn, Philippe, and Trevisiol, Emmanuelle
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- 2022
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4. Hierarchical Superhydrophobic Device to Concentrate and Precisely Localize Water-Soluble Analytes: A Route to Environmental Analysis
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Fabre, Victor, Carcenac, Franck, Laborde, Adrian, Doucet, Jean-Baptiste, Vieu, Christophe, Louarn, Philippe, and Trevisiol, Emmanuelle
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An efficient superhydrophobic concentrator is developed using a hierarchical superhydrophobic surface on which the evaporation of a sessile droplet (6 μL) drives the nonvolatile elements it contains on a predefined micrometric analytical surface (pedestal of 80 μm diameter). This hierarchical silicon surface exhibits a surface texture made of etched nanopillars and consists of micropillars and guiding lines, arranged in radial symmetry around the central pedestal. The guiding lines ensure the overall convergence of the sessile droplet toward the central pedestal during evaporation. The nanopillar texturing induced a delay in the Cassie–Baxter to Wenzel regime transition, until the edge of the droplet reaches the periphery of the pedestal. Experiments performed with polymer microparticles suspended in ultrapure water or with DNA molecules solubilized in ultrapure water at sub-fM concentrations demonstrated that the totality of the nonvolatile elements in the liquid microvolume is delivered on or close to the pedestal area, in a very reproducible manner. The very high concentration capacity of the device enabled the discrimination of the degree of purity of ultrapure water samples from different origins. The concentrator also turned out to be functional for raw water samples, opening possible applications to environmental analysis.
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- 2022
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5. First Extensive Analysis of 18F-Labeled Fluorodeoxyglucose Positron Emission Tomography-Computed Tomography in a Large Cohort of Patients With HIV-Associated Hodgkin Lymphoma: Baseline Total Metabolic Tumor Volume Affects Prognosis.
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Louarn, Nicolas, Galicier, Lionel, Bertinchamp, Rémi, Lussato, David, Montravers, Françoise, Oksenhendler, Éric, Merlet, Pascal, Gérard, Laurence, and Vercellino, Laetitia
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- 2022
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6. Ion‐Acoustic Waves Associated With Interplanetary Shocks
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Boldú, J. J., Graham, D. B., Morooka, M., André, M., Khotyaintsev, Yu. V., Dimmock, A., Píša, D., Souček, J., Maksimovic, M., Louarn, P., Fedorov, A., Nicolaou, G., and Owen, C.
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Ion‐acoustic waves (IAWs) commonly occur near interplanetary (IP) shocks. These waves are important because of their potential role in the dissipation required for collisionless shocks to exist. We study IAW occurrence statistically at different heliocentric distances using Solar Orbiter to identify the processes responsible for IAW generation near IP shocks. We show that close to IP shocks the occurrence rate of IAW increases and peaks at the ramp. In the upstream region, the IAW activity is highly variable among different shocks and increases with decreasing distance from the Sun. We show that the observed currents near IP shocks are insufficient to reach the threshold for the current‐driven instability. We argue that two‐stream proton distributions and suprathermal electrons are likely sources of the waves. Ion‐acoustic waves (IAWs) are fluctuations in the electric field that occur at frequencies close to the ion plasma frequency. These waves are commonly found in the solar wind and often cluster around interplanetary (IP) shock waves. In this study, we investigate and quantify how common IAWs are in the vicinity of IP shocks. Our research revealed that IAW activity is enhanced before and after most IP shock passages. Furthermore, IAWs are more likely to be observed preceding IP shocks that are closer to the Sun. We find that the occurrence rate of IAWs shows no clear dependence on the IP shock parameters. We explore the possible mechanisms that could explain the presence of these IAWs. For instance, IAW modes can be excited by electric currents if the associated drift velocity between ions and electrons is above a certain threshold. However, the currents alone are not strong enough to generate the IAWs found near IP shocks. We discuss other potential generation mechanisms, such as velocity distributions of ions and electrons deviating from thermodynamic equilibrium. The occurrence of Ion‐acoustic waves (IAWs) is enhanced at interplanetary (IP) shocks, peaking at the shock rampThe occurrence rate of IAWs in the upstream region of IP shocks increases with decreasing radial distance from the SunIAWs are observed upstream of an IP shock together with two‐stream protons and an electron strahl The occurrence of Ion‐acoustic waves (IAWs) is enhanced at interplanetary (IP) shocks, peaking at the shock ramp The occurrence rate of IAWs in the upstream region of IP shocks increases with decreasing radial distance from the Sun IAWs are observed upstream of an IP shock together with two‐stream protons and an electron strahl
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- 2024
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7. Electron Beams at Europa
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Allegrini, F., Saur, J., Szalay, J. R., Ebert, R. W., Kurth, W. S., Cervantes, S., Smith, H. T., Bagenal, F., Bolton, S. J., Clark, G., Connerney, J. E. P., Louarn, P., Mauk, B., McComas, D. J., Pontoni, A., Sarkango, Y., Valek, P., and Wilson, R. J.
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Jupiter's moon Europa contains a subsurface ocean whose presence is inferred from magnetic field measurements, the interpretation of which depends on knowledge of Europa's local plasma environment. A recent Juno spacecraft flyby returned new observations of plasma electrons with unprecedented resolution. Specifically, powerful magnetic field‐aligned electron beams were discovered near Europa. These beams, with energies from ∼30 to ∼300 eV, locally enhance electron‐impact‐excited emissions and ionization in Europa's atmosphere by more than a factor three over the local space environment, and are associated with large jumps of the magnetic fields. The beams therefore play an essential role in shaping Europa's plasma and magnetic field environment and thus need to be accounted for electromagnetic sounding of Europa's ocean and plume detection by future missions such as JUICE and Europa Clipper. A recent Juno spacecraft close flyby of Jupiter's moon Europa revealed the presence of powerful electrons beams. Based on previous observations and modeling of electron beams at the moon Io, such beams were not expected to be observed so close to Europa. Overall, the proximity of the beams to Europa indicates that the acceleration of these electrons takes place much closer to Europa than anticipated and that these beams, therefore, stem from a new and previously unknown acceleration mechanism. The beams are predicted to have an outsized influence on the ionization of the constituents of Europa's tenuous atmosphere and are accompanied with large magnetic field perturbations. Hence, these electron beams are an important ionization source that modify the moon's ionosphere, the electric current systems, and the magnetic field environment. In particular, the presence of electron beams will affect plasma conditions that are used to infer the extent of a subsurface ocean via the magnetic induction signal. These beams significantly impact the space plasma environment around Europa which needs to be accounted for by future missions such as ESA's (European Space Agency) JUICE (Jupiter Icy Moons Explorer) and NASA's (National Aeronautics and Space Administration) Europa Clipper mission. Powerful electron beams that significantly shape Europa's space environment are discovered during a Juno flybyThe beams enhance electron‐impact‐excited emissions in Europa's atmosphere and are associated with large jumps of the magnetic fieldsThe beams' proximity to Europa and their pitch angle distribution constrain the source acceleration to be near or within the plasma disk Powerful electron beams that significantly shape Europa's space environment are discovered during a Juno flyby The beams enhance electron‐impact‐excited emissions in Europa's atmosphere and are associated with large jumps of the magnetic fields The beams' proximity to Europa and their pitch angle distribution constrain the source acceleration to be near or within the plasma disk
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- 2024
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8. FASS results and comparison with SCIDAR and MASS
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Schreiber, Laura, Schmidt, Dirk, Vernet, Elise, Guesalaga, Andrés, Ayancán, Boris, Sarazin, Marc, Wilson, Richard W., Perera, Saavi, and Le Louarn, Miska
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- 2022
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9. A New Type of Jovian Hectometric Radiation Powered by Monoenergetic Electron Beams
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Collet, B., Lamy, L., Louis, C. K., Zarka, P., Prangé, R., Louarn, P., Kurth, W. S., and Allegrini, F.
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In this study, we statistically analyze the Jovian auroral radio sources detected in situ by Juno/Waves at frequencies fbelow the electron cyclotron frequency fce. We first conduct a survey of Juno/Waves data over 1–40 MHz from 2016 to 2022. The 15 detected HectOMetric (HOM) sources all lie within 1–5 MHz and are both less frequent than the radio sources commonly observed slightly above fceand clustered in the southern hemisphere, within ∼90–270° longitudes. We analyze these emission regions with a growth rate analysis in the framework of the Cyclotron Maser Instability (CMI), which we apply to JADE‐E high cadence electron measurements. We show that the f< fceemissions correspond to crossed radio sources, ∼300 km wide. They are located in a hot and highly depleted auroral plasma environment, along flux tubes colocated with upward field‐aligned current and at the equatorward edge of the main auroral oval. The wave amplification is consistent with the CMI and its free energy source consists of a shell‐type electron distribution function (EDF) with characteristic energies of 0.2–5keV. More energetic, 5–50 keV, shell‐type EDFs were systematically observed at higher latitudes but without any radio counterpart. Various parameters for the f< fceHOM sources, reminiscent of the ones at Earth/Saturn, are compared. Other CMI‐unstable EDFs, primarily loss cone ones, are systematically observed during the same intervals, giving rise to emission observed at fce< f< fce+ 0.5%. Our analysis thus reveals that different portions of the same EDF can be CMI‐unstable and simultaneously amplify radio waves below and above fce. Taking advantage of Juno radio, electron and magnetic measurements within the source of Jupiter's auroral radio emissions, we analyze a new type of HectOMectric (HOM, a wavelength of 1 hm matching a frequency of 3 MHz) emissions observed in situ by Juno/Waves at frequencies fbelow the electron cyclotron frequency fce. We first survey the Juno/Waves radio observations over 1–40 MHz between 2016 and 2022, covering the first 45 orbits. The 15 detected cases of f< fceemissions are much less frequent than the usual HOM emissions observed slightly above fceand their sources are inhomogeneously distributed. We then analyze these events in the framework of the Cyclotron Maser Instability (CMI) by calculating their theoretical growth rate from electron distribution functions simultaneously measured by the Juno/JADE‐E spectrometer. We show that the f< fceHOM sources are definitely consistent with the CMI powered by electron beams of 0.2–5 keV. This new type of Jovian auroral radio emission is reminiscent of the ones prominently observed at Earth and Saturn. These f< fcesources co‐exist with HOM emission at fce< f< fce+ 0.5%, which is also driven by the CMI based on different well‐known sources of free energy. A survey of Juno/Waves in situ measurement (2016–2022) reveals 15 hectometric sources observed below the local electron cyclotron frequencyWe show with a Cyclotron Maser Instability growth rate analysis using Juno/JADE‐E data that they are generated by 0.2–5 keV shell electronsThis new source of Jovian auroral radio emission is reminiscent of the auroral kilometric radiations of Earth and Saturn A survey of Juno/Waves in situ measurement (2016–2022) reveals 15 hectometric sources observed below the local electron cyclotron frequency We show with a Cyclotron Maser Instability growth rate analysis using Juno/JADE‐E data that they are generated by 0.2–5 keV shell electrons This new source of Jovian auroral radio emission is reminiscent of the auroral kilometric radiations of Earth and Saturn
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- 2024
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10. Temporal and Spatial Variability of the Electron Environment at the Orbit of Ganymede as Observed by Juno
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Pelcener, S., André, N., Nénon, Q., Rabia, J., Rojo, M., Kamran, A., Blanc, M., Louarn, P., Penou, E., Santos‐Costa, D., Allegrini, F., Ebert, R. W., Wilson, R. J., Szalay, J., Mauk, B. H., Paranicas, C., Clark, G., Bagenal, F., and Bolton, S.
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The thermal and energetic electrons along Ganymede's orbit not only weather the surface of the icy moon, but also represent a major threat to spacecraft. In this article, we rely on Juno plasma measurements to characterize the temporal and spatial variability of the electron environment upstream of Ganymede. In particular, we find that electron spectra observed by Juno have fluxes larger by a factor of 2–9 at energies above 10 keV than what was measured two decades earlier by Galileo. This result will advance our understanding of the surface weathering and may be a concern for the radiation safety of the JUICE mission. Furthermore, the June 2021 close fly‐by of Ganymede through the moon's wake reveals that the open field line regions of its magnetosphere attenuate electron fluxes at all energies by a factor of 1.6–5, thereby offering a natural shelter to visiting spacecraft crossing this region. Ganymede, the only magnetized moon in our Solar System, orbits deep inside the giant magnetosphere of Jupiter where it interacts with the temporally and spatially variable magnetized disk of plasma in corotation around the planet, its magnetodisk. The intensities of ions and electrons precipitating to the surface of Ganymede in particular depend on the location of the moon with respect to the Jovian magnetodisk. In this work, we provide a full quantification of electron properties along the orbit of Ganymede as observed by Juno. This is done by combining observations from two instruments in order to build composite electron energy spectra and derive their omnidirectional fluxes, densities, and pressures. We report that the average electron omnidirectional fluxes are significantly attenuated when measured above or below the magnetodisk, as well as strongly inside the magnetosphere of the moon where its intrinsic magnetic field provides additional shielding. We confirm that the electron total density is dominated by the thermal population, whereas the total pressure is dominated by the suprathermal one. When comparing our results with Galileo‐based observations and models, we find that the latter the latter two underestimate fluxes in particular at high energies, and we put these observations in context for the future exploration of Ganymede by JUICE. We present composite electron energy spectra combining all Juno particle data from 07/2017 to 08/2022 at Ganymede's orbitWe study the variability of electron fluxes inside and outside the Jovian magnetodisk as well as within Ganymede's magnetosphereGalileo‐based models underestimate the electron fluxes observed by Juno in particular at high energies We present composite electron energy spectra combining all Juno particle data from 07/2017 to 08/2022 at Ganymede's orbit We study the variability of electron fluxes inside and outside the Jovian magnetodisk as well as within Ganymede's magnetosphere Galileo‐based models underestimate the electron fluxes observed by Juno in particular at high energies
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- 2024
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11. Properties of Electrons Accelerated by the Ganymede‐Magnetosphere Interaction: Survey of Juno High‐Latitude Observations
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Rabia, J., Hue, V., André, N., Nénon, Q., Szalay, J. R., Allegrini, F., Sulaiman, A. H., Louis, C. K., Greathouse, T. K., Sarkango, Y., Santos‐Costa, D., Blanc, M., Penou, E., Louarn, P., Ebert, R. W., Gladstone, G. R., Mura, A., Connerney, J. E. P., and Bolton, S. J.
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The encounter between the Jovian co‐rotating plasma and Ganymede gives rise to electromagnetic waves that propagate along the magnetic field lines and accelerate particles by resonant or non‐resonant wave‐particle interaction. They ultimately precipitate into Jupiter's atmosphere and trigger auroral emissions. In this study, we use Juno/JADE, Juno/UVS data, and magnetic field line tracing to characterize the properties of electrons accelerated by the Ganymede‐magnetosphere interaction in the far‐field region. We show that the precipitating energy flux exhibits an exponential decay as a function of downtail distance from the moon, with an e‐folding value of 29°, consistent with previous UV observations from the Hubble Space Telescope (HST). We characterize the electron energy distributions and show that two distributions exist. Electrons creating the Main Alfvén Wing (MAW) spot and the auroral tail always have broadband distribution and a mean characteristic energy of 2.2 keV while in the region connected to the Transhemispheric Electron Beam (TEB) spot the electrons are distributed non‐monotonically, with a higher characteristic energy above 10 keV. Based on the observation of bidirectional electron beams, we suggest that Juno was located within the acceleration region during the 11 observations reported. We thus estimate that the acceleration region is extended, at least, between an altitude of 0.5 and 1.3 Jupiter radius above the 1‐bar surface. Finally, we estimate the size of the interaction region in the Ganymede orbital plane using far‐field measurements. These observations provide important insights for the study of particle acceleration processes involved in moon‐magnetosphere interactions. The Galilean moons orbit in a plasma‐rich environment, created by the intense volcanism of Io and transported radially outward in the Jovian magnetosphere. At the orbital locations of the moons, this plasma, co‐rotating with Jupiter, flows at a velocity significantly higher than the moons' orbital speed. Consequently, the moons disturb the plasma flow. This interaction gives rise to a set of physical processes, including the generation of electromagnetic waves that propagate away from the moons and accelerate charged particles, triggering auroral emissions by precipitating into Jupiter's atmosphere. In this study, we investigate the properties of the electrons accelerated by the Ganymede‐magnetosphere interaction. We use data from the JADE and UVS instruments onboard the Juno spacecraft as well as magnetic field line tracing methods. Following a statistical characterization of the electron properties, we compare our results with previous findings that have reported electron observations resulting from the Io‐ and Europa‐magnetosphere interactions. Juno particle and UV measurements are combined with field‐line tracing to identify 11 in situ crossings of the Ganymede flux tubeWe provide a statistical study of the accelerated electrons observed in the high‐latitude far‐field regionWe find two distinct regions in which the electrons properties, that is, characteristic energy, energy flux, and distribution, greatly differ Juno particle and UV measurements are combined with field‐line tracing to identify 11 in situ crossings of the Ganymede flux tube We provide a statistical study of the accelerated electrons observed in the high‐latitude far‐field region We find two distinct regions in which the electrons properties, that is, characteristic energy, energy flux, and distribution, greatly differ
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- 2024
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12. Outpatient healthcare and clinical trials in the care pathway: Organisational and regulatory aspects and tools
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Laviolle, Bruno, Diebolt, Vincent, Duchossoy, Luc, Anglaret, Xavier, Béhier, Jehan-Michel, Bertoye, Pierre-Henri, Chapron, Anthony, Comet, Denis, Cornu, Catherine, Fouret, Cécile, Galaup, Anne, Guérin, Aurélie, Hoen, Bruno, Imbert, Patrick, Lang, Marie, Le Louarn, Anne, Mezerette, Bastien, Sénéchal, Sophie, Simon, Tabassome, and Traineau, Pierre
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Clinical research in outpatient healthcare, particularly in general practice, which is the first line of contact with the population, is now a public health issue. However, this type of research has specific characteristics that differentiate it from clinical research conducted in a hospital setting and requires an adaptation of its conditions of practice: in terms of organisation, the development of research in outpatient healthcare relies on the appropriation of its fundamentals by the investigators, which implies their presentation, upstream, from the initial cycle, and the participation of practitioners in training modules adapted to research in primary care, such as those already organised by several GIRCI (Groupement Inter régional de la Recherche Clinique et de l’Innovation[French Interregional Clusters for Clinical Research and Innovation]). To compensate for the fragmented nature of their location, on the model of the EMRCs (équipes mobiles de recherche clinique[mobile clinical research teams]) in oncology, mobile research teams should enable general medical practices to participate in clinical trials. This presupposes, on the one hand, the allocation of earmarked funding to ensure the sustainability of a base of dedicated personnel and, on the other hand, the impetus of a national dynamic through the setting up of a multi-organisation thematic institute for “research in primary care” associated, at the operational level, with a national scale investigation network supported by a platform of excellence. The use of digital tools and innovations (telemedicine; data collection via connected tools; e-consent; electronic signature) which make it possible to digitise and relocate all or part of the research procedures for both the participant and the investigation teams. An adaptation of the legal framework in order to bring the place of research closer to the patient and not the other way round, which means moving the equipment and investigations closer to the patient. Taking into account the acceptability of the patient, thus limiting the disruption that may be caused by his or her participation in a research protocol and motivating the practitioner by valuing his or her contribution and providing all the guarantees of scientific relevance and independence of practice. In view of the contextual analysis, positive feedback and the availability of organisational and digital support points facilitating the delocalisation and digitisation of the conduct of research activity as close as possible to the patient and his or her doctor, the round table concluded that opportunities exist today which favour the development of clinical research in general practice. It is important to seize this opportunity and make the most of it without delay.
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- 2022
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13. Navigating US participant data sharing requirements: implications for international clinical trials
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Dal-Ré, Rafael, Bekker, Linda-Gail, Jha, Vivekanand, Le Louarn, Anne, and Naudet, Florian
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- 2024
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14. The adaptive optics simulation analysis tool(kit) (AOSAT)
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Schreiber, Laura, Schmidt, Dirk, Vernet, Elise, Feldt, M., Hippler, S., Cantalloube, F., Bertram, T., Obereder, A., Steuer, H., Absil, O., and Le Louarn, M.
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- 2020
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15. MAORY AO performances
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Schreiber, Laura, Schmidt, Dirk, Vernet, Elise, Agapito, Guido, Plantet, Cedric, Busoni, Lorenzo, Arcidiacono, Carmelo, Oberti, Sylvain, Verinaud, Chirstophe, Le Louarn, Miska, Puglisi, Alfio, Esposito, Simone, and Ciliegi, Paolo
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- 2020
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16. Correction of finite spatial and temporal sampling effects in stereo-SCIDAR
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Schreiber, Laura, Schmidt, Dirk, Vernet, Elise, Butterley, Timothy, Sarazin, Marc, Le Louarn, Miska, Osborn, James, and Farley, Ollie J. D.
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- 2020
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17. MAORY: the adaptive optics module for the Extremely Large Telescope (ELT)
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Schreiber, Laura, Schmidt, Dirk, Vernet, Elise, Ciliegi, Paolo, Agapito, Guido, Aliverti, Matteo, Arcidiacono, Carmelo, Balestra, Andrea, Baruffolo, Andrea, Bergomi, Maria, Bianco, Andrea, Bonaglia, Marco, Busoni, Lorenzo, Cantiello, Michele, Cascone, Enrico, Chinellato, Simonetta, Cianniello, Vincenzo, Correia, Jean-Jacques, Cosentino, Giuseppe, De Caprio, Vincenzo, Devaney, Nicholas, Di Antonio, Ivan, Di Cianno, Amico, Di Giammatteo, Ugo, Di Rico, Gianluca, Dolci, Mauro, Eredia, Christian, Farinato, Jacopo, Esposito, Simone, Fantinel, Daniela, Feautrier, Philippe, Foppiani, Italo, Giro, Enrico, Gluck, Laurance, Goncharov, Alexander, Grani, Paolo, Gullieuszik, Marco, Haguenauer, Pierre, Henault, Francois, Le Louarn, Miska, Magrin, Demetrio, Malone, Deborah, Marafatto, Luca, Munari, Matteo, Oberti, Sylvain, Pariani, Giorgio, Pettazzi, Lorenzo, Plantet, Cedric, Portaluri, Elisa, Puglisi, Alfio, Rabou, Patrick, Ragazzoni, Roberto, Rakich, Andrew, Redaelli, Edoardo, Riva, Marco, Rochat, Sylvain, Rodeghiero, Gabriele, Salasnich, Bernardo, Sordo, Rosanna, Sztefek, Marie-Helene, Valentini, Angelo, Verinaud, Christophe, Xompero, Marco, and Zoltan, Hubert
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- 2020
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18. Mitigation of truncation effects in elongated Shack–Hartmann laser guide star wavefront sensor images
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Clare, Richard M., Weddell, Stephen J., and Le Louarn, Miska
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Laser guide star Shack–Hartmann wavefront sensor images on extremely large telescopes (ELT) will be significantly elongated due to the off-axis projection of the laser relative to the subapertures. The finite number of pixels of the wavefront sensor detector means the most elongated images will be truncated, introducing errors in the centroid measurements. In this paper, we propose appending to the truncated wavefront sensor image the most likely missing tails from a high-resolution nontruncated reference image, which can be calculated from all of the low-resolution images. We show, via numerical simulation, that we can improve the centroid estimate for the most elongated subapertures on an ELT in the presence of read and photon noise.
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- 2020
19. Atomic Force Microscopy Nanomanipulation by Confocal Raman Multiwavelength Spectroscopy: Application at the Monitoring of Resonance Profile Excitation Changes of Manipulated Carbon Nanotube
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D’Orlando, Angelina, Mevellec, Jean-Yves, Louarn, Guy, and Humbert, Bernard
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This paper explores the possibilities offered by coupling C nanomanipulation with resonance Raman excitation profile approaches. We apply this method to nanostructures produced by AFM nanomanipulation. The experimental demonstration is made on the interaction between two single-wall carbon nanotubes, one semiconducting and the other metallic. The measurement is analyzed and discussed in terms of resonance shifts and broadening of the electronic transition. This paper focuses on the example of the interaction between one (18,0) metallic SWCNT with one (11,9) semiconductor SWCNT. Our experimental setup allows to measure the evolution of resonance width from 75 cm–1to 100 cm–1for an isolated carbon nanotube (CNT), to more than 200 cm–1for interacting CNTs.
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- 2020
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20. Alfvénic velocity spikes and rotational flows in the near-Sun solar wind
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Kasper, J. C., Bale, S. D., Belcher, J. W., Berthomier, M., Case, A. W., Chandran, B. D. G., Curtis, D. W., Gallagher, D., Gary, S. P., Golub, L., Halekas, J. S., Ho, G. C., Horbury, T. S., Hu, Q., Huang, J., Klein, K. G., Korreck, K. E., Larson, D. E., Livi, R., Maruca, B., Lavraud, B., Louarn, P., Maksimovic, M., Martinovic, M., McGinnis, D., Pogorelov, N. V., Richardson, J. D., Skoug, R. M., Steinberg, J. T., Stevens, M. L., Szabo, A., Velli, M., Whittlesey, P. L., Wright, K. H., Zank, G. P., MacDowall, R. J., McComas, D. J., McNutt, R. L., Pulupa, M., Raouafi, N. E., and Schwadron, N. A.
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The prediction of a supersonic solar wind1was first confirmed by spacecraft near Earth2,3and later by spacecraft at heliocentric distances as small as 62 solar radii4. These missions showed that plasma accelerates as it emerges from the corona, aided by unidentified processes that transport energy outwards from the Sun before depositing it in the wind. Alfvénic fluctuations are a promising candidate for such a process because they are seen in the corona and solar wind and contain considerable energy5–7. Magnetic tension forces the corona to co-rotate with the Sun, but any residual rotation far from the Sun reported until now has been much smaller than the amplitude of waves and deflections from interacting wind streams8. Here we report observations of solar-wind plasma at heliocentric distances of about 35 solar radii9–11, well within the distance at which stream interactions become important. We find that Alfvén waves organize into structured velocity spikes with duration of up to minutes, which are associated with propagating S-like bends in the magnetic-field lines. We detect an increasing rotational component to the flow velocity of the solar wind around the Sun, peaking at 35 to 50 kilometres per second—considerably above the amplitude of the waves. These flows exceed classical velocity predictions of a few kilometres per second, challenging models of circulation in the corona and calling into question our understanding of how stars lose angular momentum and spin down as they age12–14.
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- 2019
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21. Total and partial ossiculoplasty in children: Audiological results and predictive factors.
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Dumont, J., Abouzayd, M., Le Louarn, A., Pondaven, S., Bakhos, D., and Lescanne, E.
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EAR ossicles ,DEMOGRAPHIC databases ,INTRAOPERATIVE care ,PROSTHETICS ,TYMPANOPLASTY - Abstract
To assess ossiculoplasty results in children and screen for predictive factors of efficacy. Seventy five children undergoing ossiculoplasty between 2001 and 2014 in a pediatric ENT department were included. The following data were collected and analyzed: demographic data, surgical indication, history of tympanoplasty, contralateral ear status (healthy, affected), preoperative hearing thresholds, surgical technique, intraoperative findings, and ossicular chain status at eardrum opening. Audiological results were reported according to American Academy of Otolaryngology-Head and Neck Surgery guidelines. Forty eight patients were included in the total ossicular reconstruction prosthesis (TORP) group. Mean age at surgery was 9.9 years. Mean follow up was 2.7 years. Mean air-bone gap (ABG) closure to within 20 dB was achieved in 40% of cases at medium term (12 to 18 months after surgery). Air conduction (AC) threshold ≤ 30 dB was achieved in 68% of cases. AC threshold improved by 14.6 dB and 8.7 dB at medium and long-term follow-up, respectively. A significant correlation was found between success rate and absence of history of tympanoplasty. The success rate was higher for primary than for revision procedures. Twenty seven children were included in the partial ossicular reconstruction prosthesis (PORP) group. Mean age was 9.5 years, and mean follow-up 2.6 years. Mean air-bone gap (ABG) closure to within 20 dB was achieved in 75% of cases at medium term. AC threshold ≤ 30 dB was achieved in 75% of cases AC threshold improved by 9.3 dB and 5 dB at medium and long-term follow-up, respectively. No predictive factors for success were found in the PORP group. The present study suggested that total ossiculoplasty leads to better results when performed in first-line. It also confirmed that functional outcome is better in partial than total ossicular reconstruction prosthesis. [ABSTRACT FROM AUTHOR]
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- 2019
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22. Thickness Limitation of Band-to-Band Tunneling Process in GaAsSb/InGaAs Type-II Tunnel Junctions Designed for Multi-Junction Solar Cells.
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Louarn, K., Claveau, Y., Fontaine, C., Arnoult, A., Marigo-Lombart, L., Massiot, I., Piquemal, F., Bounouh, A., Cavassilas, N., and Almuneau, G.
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- 2019
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23. Source of Radio Emissions Induced by the Galilean Moons Io, Europa and Ganymede: In Situ Measurements by Juno
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Louis, C. K., Louarn, P., Collet, B., Clément, N., Al Saati, S., Szalay, J. R., Hue, V., Lamy, L., Kotsiaros, S., Kurth, W. S., Jackman, C. M., Wang, Y., Blanc, M., Allegrini, F., Connerney, J. E. P., and Gershman, D.
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At Jupiter, part of the auroral radio emissions are induced by the Galilean moons Io, Europa and Ganymede. Until now, except for Ganymede, they have been only remotely detected, using ground–based radio–telescopes or electric antennas aboard spacecraft. The polar trajectory of the Juno orbiter allows the spacecraft to cross the range of magnetic flux tubes which sustain the various Jupiter–satellite interactions, and in turn to sample in situ the associated radio emission regions. In this study, we focus on the detection and the characterization of radio sources associated with Io, Europa and Ganymede. Using electric wave measurements or radio observations (Juno/Waves), in situ electron measurements (Juno/JADE–E), and magnetic field measurements (Juno/MAG) we demonstrate that the Cyclotron Maser Instability (CMI) driven by a loss–cone electron distribution function is responsible for the encountered radio sources. We confirmed that radio emissions are associated with Main (MAW) or Reflected Alfvén Wing (RAW), but also show that for Europa and Ganymede, induced radio emissions are associated with Transhemispheric Electron Beam (TEB). For each traversed radio source, we determine the latitudinal extension, the CMI–resonant electron energy, and the bandwidth of the emission. We show that the presence of Alfvén perturbations and downward field–aligned currents are necessary for the radio emissions to be amplified. At Jupiter, the auroras are much more intense and long‐lasting than on Earth, and some are influenced by Jupiter's three largest moons: Io, Europa, and Ganymede. We're particularly interested in the radio signals from these auroras. Until recently, these signals were mainly studied from a distance, using Earth‐based telescopes or spacecraft passing by Jupiter. However, since 2016, the Juno spacecraft has been orbiting Jupiter, flying through the auroral zone. Our study investigates the creation of these radio auroras using Juno's instruments to measure radio waves, particles, and magnetic fields. Our research strongly suggests that a phenomenon called the Cyclotron Maser Instability is the cause of these radio signals. This instability happens because some electrons are not coming back from Jupiter after causing Ultraviolet aurora on top of Jupiter's atmosphere. These radio signals are connected to the moons' ultraviolet auroras. Additionally, our research highlights the importance of specific perturbations in Jupiter's magnetic field, known as Alfvén perturbations, and currents that link Jupiter to these moons. This study deepens our understanding of Jupiter‐moon interactions and sheds light on Jupiter's fascinating auroras. All Jupiter‐moon radio emissions are shown to be similarly triggered by the CMIThe crossed radio sources are colocated with either MAW, RAW or TEB footprintsThe crossed radio sources coincide with downward field‐aligned currents and Alfvén perturbations All Jupiter‐moon radio emissions are shown to be similarly triggered by the CMI The crossed radio sources are colocated with either MAW, RAW or TEB footprints The crossed radio sources coincide with downward field‐aligned currents and Alfvén perturbations
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- 2023
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24. Challenges in recording race and ethnicity data in biomedical research: the French and Swedish perspectives
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Yordanov, Youri, Le Louarn, Anne, and Khoshnood, Ardavan
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- 2023
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25. Gas Analysis by Electron Ionization Combined with Chemical Ionization in a Compact FTICR Mass Spectrometer.
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Heninger, Michel, Mestdagh, Hélène, Louarn, Essyllt, Mauclaire, Gérard, Boissel, Pierre, Leprovost, Julien, Bauchard, Elsa, Thomas, Sébastien, and Lemaire, Joël
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- 2018
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26. Jovian High‐Latitude Ionospheric Ions: Juno In Situ Observations
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Valek, P. W., Allegrini, F., Bagenal, F., Bolton, S. J., Connerney, J. E. P., Ebert, R. W., Kim, T. K., Levin, S. M., Louarn, P., Mccomas, D. J., Szalay, J. R., Thomsen, M. F., and Wilson, R. J.
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The low‐altitude, high‐velocity trajectory of the Juno spacecraft enables the Jovian Auroral Distributions Experiment to make the first in situ observations of the high‐latitude ionospheric plasma. Ions are observed to energies below 1 eV. The high‐latitude ionospheric ions are observed simultaneously with a loss cone in the magnetospheric ions, suggesting precipitating magnetospheric ions contribute to the heating of the upper ionosphere, raising the scale height, and pushing ionospheric ions to altitudes of 0.5 RJabove the planet where they are observed by Jovian Auroral Distributions Experiment. The source of the magnetospheric ions is tied to the Io torus and plasma sheet, indicated by the cutoff seen in both the magnetospheric and ionospheric plasma at the Io M‐shells. Equatorward of the Io M‐shell boundary, the ionospheric ions are not observed, indicating a drop in the scale height of the ionospheric ions at those latitudes. The Jovian Auroral Distributions Experiment (JADE) ion sensor has made the first in situ observations of the upper, high‐latitude ionosphere of Jupiter. Flown on the Juno spacecraft, JADE observes the ionosphere at altitudes of approximately half a Jovian radii, with the spacecraft traveling at the high speed of ~50 km/s. For comparison, a proton traveling at 50 km/s has an energy of approximately 10 eV. The combination of the low‐altitude and high ram velocity enables JADE to measure ionospheric ions to energies below 1 eV. These observations reveal a cold ionospheric population of protons at high latitudes, seen coincident with precipitating magnetospheric ions. This indicates that the precipitating magnetospheric ions heat the upper ionosphere, raising the height where these protons can be observed. The ionospheric protons are seen in bands in the northern and southern latitudes, bounded on the equator edge by the field lines that connect to Io, and inside the auroral oval to the poleward side. The high‐latitude ionosphere is observed between the magnetic latitudes bounded by the auroral oval and Io's magnetic flux shellTwo populations are observed at high latitudes: (1) magnetospheric ions consisting of H, S, and O ions and (2) cold ionospheric H+ionsObservation of a loss cone suggests precipitating magnetospheric ions heat the upper ionosphere to heights ~0.5 RJabove the clouds
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- 2019
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27. Nanostructured surface coatings for titanium alloy implants
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Louarn, Guy, Salou, Laetitia, Hoornaert, Alain, and Layrolle, Pierre
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Abstract
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- 2019
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28. Ossiculoplasties totales et partielles de l’enfant : résultats audiométriques et facteurs prédictifs d’efficacité
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Dumont, J., Abouzayd, M., Le Louarn, A., Pondaven, S., Bakhos, D., and Lescanne, E.
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Étudier les résultats de l’ossiculoplastie dans une série pédiatrique et rechercher les facteurs prédictifs d’efficacité.
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- 2019
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29. Comparing Electron Energetics and UV Brightness in Jupiter's Northern Polar Region During Juno Perijove 5
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Ebert, R. W., Greathouse, T. K., Clark, G., Allegrini, F., Bagenal, F., Bolton, S. J., Connerney, J. E. P., Gladstone, G. R., Imai, M., Hue, V., Kurth, W. S., Levin, S., Louarn, P., Mauk, B. H., McComas, D. J., Paranicas, C., Szalay, J. R., Thomsen, M. F., Valek, P. W., and Wilson, R. J.
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We compare electron and UV observations mapping to the same location in Jupiter's northern polar region, poleward of the main aurora, during Juno perijove 5. Simultaneous peaks in UV brightness and electron energy flux are identified when observations map to the same location at the same time. The downward energy flux during these simultaneous observations was not sufficient to generate the observed UV brightness; the upward energy flux was. We propose that the primary acceleration region is below Juno's altitude, from which the more intense upward electrons originate. For the complete interval, the UV brightness peaked at ~240 kilorayleigh (kR); the downward and upward energy fluxes peaked at 60 and 700 mW/m2, respectively. Increased downward energy fluxes are associated with increased contributions from tens of keV electrons. These observations provide evidence that bidirectional electron beams with broad energy distributions can produce tens to hundreds of kilorayleigh polar UV emissions. Jupiter's ultraviolet (UV) aurora is produced by electrons that precipitate into the planet's atmosphere and interact with hydrogen molecules. A number of different UV auroral emission regions have been identified such as the main aurora, the aurora associated with Jupiter's satellites, and the polar aurora located poleward of the main aurora. We examine electron and UV observations from Juno in Jupiter's northern polar region to investigate the processes responsible for producing Jupiter's polar aurora. We show electrons and UV emissions having simultaneous enhancements during a time when they map to the same location of Jupiter's upper atmosphere at the same time. We present evidence that electrons with energies between 0.1 and 100 kilo electron volts (keV) are capable of producing the polar UV emissions studied here and that further acceleration of these electrons may be occurring at altitudes below the spacecraft. Simultaneous peaks are observed in electron energy flux and UV brightness when they map to same location in Jupiter's polar region at the same timeUpward greater than downward electron energy fluxes are observed, suggesting that primary acceleration region may be below ~1.5 jovian radiiDownward energy fluxes able to produce tens to hundreds of kilorayleigh polar UV emissions are identified; increases in energy flux due to tens of keV electrons
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- 2019
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30. In Situ Observations Connected to the Io Footprint Tail Aurora
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Szalay, J. R., Bonfond, B., Allegrini, F., Bagenal, F., Bolton, S., Clark, G., Connerney, J. E. P., Ebert, R. W., Ergun, R. E., Gladstone, G. R., Grodent, D., Hospodarsky, G. B., Hue, V., Kurth, W. S., Kotsiaros, S., Levin, S. M., Louarn, P., Mauk, B., McComas, D. J., Saur, J., Valek, P. W., and Wilson, R. J.
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The Juno spacecraft crossed flux tubes connected to the Io footprint tail at low Jovian altitudes on multiple occasions. The transits covered longitudinal separations of approximately 10° to 120° along the footprint tail. Juno's suite of magnetospheric instruments acquired detailed measurements of the Io footprint tail. Juno observed planetward electron energy fluxes of ~70 mW/m2near the Io footprint and ~10 mW/m2farther down the tail, along with correlated, intense electric and magnetic wave signatures, which also decreased down the tail. All observed electron distributions were broad in energy, suggesting a dominantly broadband acceleration process, and did not show any broad inverted‐Vstructure that would be indicative of acceleration by a quasi‐static, discrete, parallel potential. Observed waves were primarily below the proton cyclotron frequency, yet identification of a definitive wave mode is elusive. Beyond 40° down the footprint tail, Juno observed depleted upward loss cones, suggesting that the broadband acceleration occurred at distances beyond Juno's transit distance of 1.3 to 1.7 RJ. For all transits, Juno observed fine structure on scales of approximately tens of kilometers and confirmed independently with electron and wave measurements that a bifurcated tail can intermittently exist. The Juno spacecraft crossed regions magnetically connected to auroral structures associated with Jupiter's moon Io on multiple occasions. The transits covered longitudinal separations of approximately 10° to 120° along Io's auroral tail. Juno's suite of instruments acquired detailed measurements of these auroral structures. Juno directly observed the electrons that sustain these auroral features before they crash into the atmosphere and generate the brilliant aurora. The flux of these electrons decreased as Juno transited the tail farther from Io's longitude. While there are two main explanations for Io's auroral signatures, the nature of the observed electrons in this work favors one mechanism over the other. When Juno was far from Io's longitude, the observations suggest that the spacecraft was below the point at which the electrons are accelerated into the atmosphere. For all transits, Juno observed fine structure on scales of approximately tens of kilometers and confirmed that a bifurcated tail can intermittently exist. Juno crossed flux tubes connected to Io's footprint tail aurora 10° to 120° downstream of the main Alfven wing (MAW) spotBroad power law‐like electron energy distributions suggest a primarily broadband acceleration mechanismJuno observed structure with ~20‐km resolution, bifurcated tails, and broadening with longitudinal separation from the MAW spot
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- 2018
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31. Effect of a Magnetospheric Compression on Jovian Radio Emissions: In Situ Case Study Using Juno Data
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Louis, C. K., Jackman, C. M., Hospodarsky, G., O’Kane Hackett, A., Devon‐Hurley, E., Zarka, P., Kurth, W. S., Ebert, R. W., Weigt, D. M., Fogg, A. R., Waters, J. E., McEntee, S. C., Connerney, J. E. P., Louarn, P., Levin, S., and Bolton, S. J.
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During its polar orbits around Jupiter, Juno often crosses the boundaries of the Jovian magnetosphere (namely the magnetopause and bow shock). From the boundary locations, the upstream solar wind dynamic pressure can be inferred, which in turn illustrates the state of compression or relaxation of the system. The aim of this study is to examine Jovian radio emissions during magnetospheric compressions, in order to determine the relationship between the solar wind and Jovian radio emissions. In this paper, we give a complete list of bow shock and magnetopause crossings (from June 2016 to August 2022), and the associated solar wind dynamic pressure and standoff distances inferred from Joy et al. (2002, https://doi.org/10.1029/2001JA009146). We then select two sets of magnetopause crossings with moderate to strong compression of the magnetosphere for two case studies of the response of the Jovian radio emissions. We confirm that magnetospheric compressions lead to the activation of new radio sources. Newly activated broadband kilometric emissions are observed almost simultaneously with compression of the magnetosphere, with sources covering a large range of longitudes. Decametric emission sources are seen to be activated more than one rotation later only at specific longitudes and dusk local times. Finally, the activation of narrowband kilometric radiation is not observed until the magnetosphere is in its expansion phase. This paper provides a list of the Jovian magnetosphere boundary crossings by the Juno spacecraft from June 2016 to August 2022Jovian magnetospheric compressions lead to increased bKOM radio emissions (immediately) and DAM on the dusk sector (more than one rotation later)nKOM radio emission appears later during relaxation phase of the compression This paper provides a list of the Jovian magnetosphere boundary crossings by the Juno spacecraft from June 2016 to August 2022 Jovian magnetospheric compressions lead to increased bKOM radio emissions (immediately) and DAM on the dusk sector (more than one rotation later) nKOM radio emission appears later during relaxation phase of the compression
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- 2023
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32. Observation of Electron Conics by Juno: Implications for Radio Generation and Acceleration Processes
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Louarn, P., Allegrini, F., McComas, D. J., Valek, P. W., Kurth, W. S., André, N., Bagenal, F., Bolton, S., Ebert, R. W., Imai, M., Levin, S., Szalay, J. R., and Wilson, R. J.
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Using Juno plasma, electric and magnetic field observations (from JADE, Waves, and MAG instruments), we show that electron conic distributions are commonly observed in Jovian radio sources. The conics are characterized by maximum fluxes at oblique pitch angles, ~20°–30° from the B field, both in the upward and downward directions. They constitute an efficient source of free energy for the cyclotron maser instability. Growth rates of ~3 to 7 × 104s−1are obtained for hectometric waves, leading to amplification by e10with propagation paths of 50–100 km. We show that stochastic acceleration due to interactions with a low‐frequency electric field turbulence located a few 104km above the ionosphere may form the observed conics. A possible source of turbulence could be inertial Alfvén waves, suggesting a connection between the auroral acceleration and generation of coherent radio emissions. Jupiter, as many astrophysical magnetized objects, is a powerful emitter of nonthermal radio emissions. The coherent process required for their generation is likely the cyclotron maser instability (CMI). However, the exact conditions of wave amplification are not known precisely at Jupiter. With Juno mission, for the first time, it is possible to explore the auroral regions of Jupiter, where the particles are accelerated and the nonthermal emissions produced. With several crossing of the radio sources, the free energy used by the CMI can now be identified. It corresponds to conic‐likedistributions, characterized by an accumulation of particles just outside the loss cones. Applying the CMI theory, large growth rates are obtained, showing that the conics probably play a central role in the wave generation source. The formation of the conics could be due to an interaction with a low‐frequency Alfvénic turbulence. This suggests a close relationship between the radio wave generation and the particle acceleration, as at Earth, the details of the scenario being, nevertheless, slightly different. Electron conics are observed by Juno in Jovian radio sources, and their role in the wave amplification is analyzedThe observed conics may very efficiently drive the cyclotron maser, from decametric to kilometric wavelength rangesThe formation of conics is modeled by a stochastic acceleration due to a low‐frequency parallel electric field turbulence
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- 2018
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33. Representative atmospheric turbulence profiles for ESO Paranal
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Close, Laird M., Schreiber, Laura, Schmidt, Dirk, Farley, O. J. D., Osborn, J., Wilson, R. W., Butterley, T., Laidlaw, D., Townson, M., Morris, T., Sarazin, M., Derie, F., Le Louarn, M., Chacón, A., Haubois, X., Navarrete, J., and Milli, J.
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- 2018
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34. The AO in AOF
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Close, Laird M., Schreiber, Laura, Schmidt, Dirk, Oberti, Sylvain, Kolb, Johann, Madec, Pierre-Yves, Haguenauer, Pierre, Le Louarn, Miska, Pettazzi, Lorenzo, Guesalaga, Andres, Donaldson, Robert, Soenke, Christian, Jeram, Bogdan, Suárez Valles, Marcos, Kiekebusch, Mario, Argomedo, Javier, La Penna, Paolo, Paufique, Jerome, Arsenault, Robin, Hubin, Norbert, and Vernet, Joel
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- 2018
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35. Improvements to MASS turbulence profile estimation at Paranal
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Close, Laird M., Schreiber, Laura, Schmidt, Dirk, Butterley, Timothy, Sarazin, Marc, Navarrete, Julio, Osborn, James, Farley, Ollie, and Le Louarn, Miska
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- 2018
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36. Effects of the telescope spider on extreme adaptive optics systems with pyramid wavefront sensors
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Close, Laird M., Schreiber, Laura, Schmidt, Dirk, Engler, Byron, Weddell, Steve, Le Louarn, Miska, and Clare, Richard
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- 2018
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37. Sédation profonde et continue maintenue jusqu’au décès : retour d’expérience d’une équipe mobile de soins palliatifs
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Plançon, Morgane and Louarn, Catherine
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La loi dite « Clayes-Leonetti » modifie les pratiques de soins et les réflexions des équipes. Elle impose notamment la présence d’un médecin consultant lors des échanges relatifs à la mise en place de la sédation profonde et continue maintenue jusqu’au décès, positionnant les équipes de soins palliatifs en première ligne, de par la nouveauté et la complexité de ces situations. Notre équipe mobile de soins palliatifs est régulièrement sollicitée et c’est à travers la lecture de plusieurs situations cliniques que nous avons souhaité explorer ce que la loi a pu modifier dans nos pratiques. Il faut en effet noter que les modifications législatives peuvent générer des situations nouvelles, pourvoyeuses de dilemmes éthiques et cliniques ou de difficultés morales pour chacun, qu’il s’agit quotidiennement de mettre en mouvement au sein des équipes de soins, de façon à parvenir à asseoir une pratique clinique sécurisante pour les patients et les soignants.
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- 2018
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38. Evidence for Non‐Monotonic and Broadband Electron Distributions in the Europa Footprint Tail Revealed by Juno In Situ Measurements
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Rabia, J., Hue, V., Szalay, J. R., André, N., Nénon, Q., Blanc, M., Allegrini, F., Bolton, S. J., Connerney, J. E. P., Ebert, R. W., Gladstone, G. R., Greathouse, T. K., Louarn, P., Mura, A., Penou, E., and Sulaiman, A. H.
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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, ranging from 34 to 0.8 mW/m2, exhibits an exponential decay as a function of downtail distance, with an e‐folding factor of 7.4°. Electrons are accelerated at energies between 0.3 and 25 keV, with a characteristic energy that decreases downtail. The electron distributions form non‐monotonic spectra in the near tail (i.e., within an angular separation of less than 4°) that become broadband in the far tail. The size of the interaction region at the equator is estimated to be 4.2 ± 0.9 Europa radii, consistent with previous estimates based on theory and UV observations. The space environment close to Jupiter is dominated by the magnetic field of the giant planet in a so‐called magnetosphere. The four Galilean moons, including Europa, orbit deep inside the Jovian magnetosphere and therefore constantly interact with the rapidly rotating plasma flow made of charged particles trapped by the magnetic field of the giant planet. The interaction between moons and plasma generates electromagnetic waves, accelerate particles and produce emissions at various wavelengths, including bright UV auroral spots and tails in the atmosphere of Jupiter. In this work, we present 10 events where the Juno spacecraft observed both in situ and remotely the acceleration of electrons due to the interaction between the icy moon Europa and the magnetospheric environment. We characterize the properties of the accelerated electrons. In particular, we find that acceleration is maximum near the moon itself, and that two distinct families of electron distributions exist. Juno unambiguously observed 10 events of downward electron acceleration from Europa at various downtail separations with the moonPrecipitating energy fluxes decrease exponentially as a function of downtail distance from the moon, with an e‐folding of 7.4°Two types of electron distributions exist: non‐monotonic in the near tail and broadband in the far tail Juno unambiguously observed 10 events of downward electron acceleration from Europa at various downtail separations with the moon Precipitating energy fluxes decrease exponentially as a function of downtail distance from the moon, with an e‐folding of 7.4° Two types of electron distributions exist: non‐monotonic in the near tail and broadband in the far tail
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- 2023
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39. Spatial Distribution and Properties of 0.1–100 keV Electrons in Jupiter's Polar Auroral Region
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Ebert, R. W., Allegrini, F., Bagenal, F., Bolton, S. J., Connerney, J. E. P., Clark, G., Gladstone, G. R., Hue, V., Kurth, W. S., Levin, S., Louarn, P., Mauk, B. H., McComas, D. J., Paranicas, C., Reno, M., Saur, J., Szalay, J. R., Thomsen, M. F., Valek, P., Weidner, S., and Wilson, R. J.
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We present observations of 0.1–100 keV electrons from Juno's Jovian Auroral Distributions Experiment Electron instrument over Jupiter's polar auroral region for periods around four Juno perijoves (PJ1, PJ3, PJ4, and PJ5). The observations reveal regions containing magnetic field aligned beams of bidirectional electrons having broad energy distributions interspersed between beams of upward electrons with narrow, peaked energy distributions, regions void of these electrons, and regions dominated by penetrating radiation. The electrons show evidence of acceleration via parallel electric fields (inverted‐V structures) and via stochastic processes (bidirectional distributions). The inverted‐V structures shown here were observed from ~1.4 to 2.9 RJand had spatial scales of hundreds to thousands of kilometers along Juno's trajectory. The upward electron energy flux was typically greater than the downward flux, the latter ranging between ~0.01 and 5 mW m−2for two cases shown here which we estimate could produce ~0.1–50 kR of ultraviolet emission. JADE observed 0.1–100 keV electrons, regions void of these electrons, and regions of penetrating radiation in Jupiter's polar aurora regionThe electrons consisted of bidirectional beams with broad energies interspersed between upward beams having narrow energy distributionsThe energy flux of downward electrons shown here ranged from ~0.01 to 5 mW m−2, the upward flux being up to ~100 times larger We report on observations of 0.1 ‐ 100 kilo‐electron volt electrons from the Jovian Auroral Distributions Experiment Electron instrument (JADE‐E) on Juno over the region where Jupiter's ultraviolet (UV) polar aurora is produced. The observations show electrons moving both towards and away from Jupiter. These electrons show both broad and narrow energy distributions, suggesting the presence of at least two different acceleration mechanisms. Regions void of these electrons and regions dominated by penetrating radiation were also identified. The energy flux of the electrons moving towards Jupiter was sufficient to produce the weaker UV polar auroral emissions observed at Jupiter but a different source of electrons, likely with higher energies, is required to account for the brighter emissions.
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- 2017
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40. Preliminary results from the Stereo-SCIDAR at the VLT Observatory: extraction of reference atmospheric turbulence profiles for E-ELT adaptive optics instrument performance simulations
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Stein, Karin U., Gladysz, Szymon, Sarazin, Marc S., Osborn, James, Chacon-Oelckers, Arlette, Dérie, Frédéric J., Le Louarn, Miska, Milli, Julien, Navarrete, Julio, and Wilson, Richard R. W.
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- 2017
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41. Hot flow anomaly observed at Jupiter's bow shock
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Valek, P. W., Thomsen, M. F., Allegrini, F., Bagenal, F., Bolton, S., Connerney, J., Ebert, R. W., Gladstone, R., Kurth, W. S., Levin, S., Louarn, P., Mauk, B., McComas, D. J., Pollock, C., Reno, M., Szalay, J. R., Weidner, S., and Wilson, R. J.
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A Hot Flow Anomaly (HFA) is created when an interplanetary current sheet interacts with a planetary bow shock. Previous studies have reported observing HFAs at Earth, Mercury, Venus, Mars, and Saturn. During Juno's approach to Jupiter, a number of its instruments operated in the solar wind. Prior to crossing into Jupiter's magnetosphere, Juno observed an HFA at Jupiter for the first time. This Jovian HFA shares most of the characteristics of HFAs seen at other planets. The notable exception is that the Jovian HFA is significantly larger than any HFA seen before. With an apparent size greater than 2 × 106km the Jovian HFA is orders of magnitude larger than those seen at the other planets. By comparing the size of the HFAs at the other planets with the Jovian HFA, we conclude that HFAs size scales with the size of planetary bow shocks that the interplanetary current sheet interacts with. Observations from Juno of the first Hot Flow Anomaly detected at Jupiter's bow shockSize of Jovian Hot Flow Anomaly is orders of magnitude larger than those seen at other planetsSize of Hot Flow Anomalies scale with the size of the bow shock of the planet
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- 2017
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42. Plasma measurements in the Jovian polar region with Juno/JADE
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Szalay, J. R., Allegrini, F., Bagenal, F., Bolton, S., Clark, G., Connerney, J. E. P., Dougherty, L. P., Ebert, R. W., Gershman, D. J., Kurth, W. S., Levin, S., Louarn, P., Mauk, B., McComas, D. J., Paranicas, C., Ranquist, D., Reno, M., Thomsen, M. F., Valek, P. W., Weidner, S., and Wilson, R. J.
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Jupiter's main auroral oval provides a window into the complex magnetospheric dynamics of the Jovian system. The Juno spacecraft entered orbit about Jupiter on 5 July 2016 and carries on board the Auroral Distributions Experiment (JADE) that can directly sample the auroral plasma structures. Here we identify five distinct regimes in the JADE data based on composition/energy boundaries and magnetic field mappings, which exhibit considerable symmetry between the northern and southern passes. These intervals correspond to periods when Juno was connected to the Io torus, inner plasma sheet, middle plasma sheet, outer plasma sheet, and the polar region. When connected to the torus and inner plasma sheet, the heavy ions are consistent with a corotating pickup population. For Juno's first perijove, we do not find evidence for a broad auroral acceleration region at Jupiter's main auroral oval for energies below 100 keV. Juno/JADE made high temporal resolution measurements at high latitudes of the Io torus and plasma sheet plasma populationsWe identify regions where Juno was connected to the Io torus, inner plasma sheet, middle plasma sheet, outer plasma sheet, and high‐latitude polar regionFor JADE's first auroral transits at ~0.7 RJaltitude and <100 keV, we find no evidence for a broad Jovian auroral acceleration region
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- 2017
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43. Electron beams and loss cones in the auroral regions of Jupiter
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Allegrini, F., Bagenal, F., Bolton, S., Connerney, J., Clark, G., Ebert, R. W., Kim, T. K., Kurth, W. S., Levin, S., Louarn, P., Mauk, B., McComas, D. J., Pollock, C., Ranquist, D., Reno, M., Szalay, J. R., Thomsen, M. F., Valek, P., Weidner, S., Wilson, R. J., and Zink, J. L.
- Abstract
We report on the first observations of 100 eV to 100 keV electrons over the auroral regions of Jupiter by the Jovian Auroral Distributions Experiment (JADE) on board the Juno mission. The focus is on the regions that were magnetically connected to the main auroral oval. Amongst the most remarkable features, JADE observed electron beams, mostly upward going but also some downward going in the south, at latitudes from ~69° to 72° and ~ −66° to −70° corresponding to M shells (“M” for magnetic) from ~18 to 54 and ~28 to 61, respectively. The beams were replaced by upward loss cones at lower latitudes. There was no evidence of strongly accelerated downward electrons analogous to the auroral “inverted Vs” at Earth. Rather, the presence of upward loss cones suggests a diffuse aurora process. The energy spectra resemble tails of distributions or power laws (suggestive of a stochastic acceleration process) but can also have some clear enhancements or even peaks generally between 1 and 10 keV. Electron intensities change on timescales of a second or less at times implying that auroral structures can be of the order of a few tens of kilometers. First 100 eV to 100 keV electron measurements in the auroral regions of JupiterUpward and downward electron beams observed in the polar regions and on field lines connected to the middle plasma sheetUpward loss cone on the field lines connected to the inner plasma sheet suggesting a diffuse aurora process
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- 2017
- Full Text
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44. A new view of Jupiter's auroral radio spectrum
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Kurth, W. S., Imai, M., Hospodarsky, G. B., Gurnett, D. A., Louarn, P., Valek, P., Allegrini, F., Connerney, J. E. P., Mauk, B. H., Bolton, S. J., Levin, S. M., Adriani, A., Bagenal, F., Gladstone, G. R., McComas, D. J., and Zarka, P.
- Abstract
Juno's first perijove science observations were carried out on 27 August 2016. The 90° orbit inclination and 4163 km periapsis altitude provide the first opportunity to explore Jupiter's polar magnetosphere. A radio and plasma wave instrument on Juno called Waves provided a new view of Jupiter's auroral radio emissions from near 10 kHz to ~30 MHz. This frequency range covers the classically named decametric, hectometric, and broadband kilometric radio emissions, and Juno observations showed much of this entire spectrum to consist of V‐shaped emissions in frequency‐time space with intensified vertices located very close to the electron cyclotron frequency. The proximity of the radio emissions to the cyclotron frequency along with loss cone features in the energetic electron distribution strongly suggests that Juno passed very close to, if not through, one or more of the cyclotron maser instability sources thought to be responsible for Jupiter's auroral radio emissions. First polar view of Jupiter's auroral radio emissionsEmissions composed of multiple V‐shaped spectral featuresJuno passed close to or through five or more source regions
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- 2017
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45. Generation of the Jovian hectometric radiation: First lessons from Juno
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Louarn, P., Allegrini, F., McComas, D. J., Valek, P. W., Kurth, W. S., André, N., Bagenal, F., Bolton, S., Connerney, J., Ebert, R. W., Imai, M., Levin, S., Szalay, J. R., Weidner, S., Wilson, R. J., and Zink, J. L.
- Abstract
Using Juno plasma and wave and magnetic observations (JADE and Waves and MAG instruments), the generation mechanism of the Jovian hectometric radio emission is analyzed. It is shown that suitable conditions for the cyclotron maser instability (CMI) are observed in the regions of the radio sources. Pronounced loss cone in the electron distributions are likely the source of free energy for the instability. The theory reveals that sufficient growth rates are obtained from the distribution functions that are measured by the JADE‐Electron instrument. The CMI would be driven by upgoing electron populations at 5–10 keV and 10–30° pitch angle, the amplified waves propagating at 82°–87° from the Bfield, a fraction of a percent above the gyrofrequency. Typical e‐folding times of 10−4s are obtained, leading to an amplification path of ~1000 km. Overall, this scenario for generation of the Jovian hectometric waves differs significantly from the case of the auroral kilometric radiation at Earth. First detailed wave/particle investigation in a Jovian radio source, using JADE, Waves, and MAG Juno instrumentsConfirmation that the cyclotron maser instability is the generation mechanismDemonstration that the observed loss cone distributions provide sufficient growth rates to explain the wave amplification
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- 2017
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46. Plasma environment at the dawn flank of Jupiter's magnetosphere: Juno arrives at Jupiter
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McComas, D. J., Szalay, J. R., Allegrini, F., Bagenal, F., Connerney, J., Ebert, R. W., Kurth, W. S., Louarn, P., Mauk, B., Reno, M., Thomsen, M. F., Valek, P., Weidner, S., Wilson, R. J., and Bolton, S.
- Abstract
This study examines the first observations from the Jovian Auroral Distributions Experiment (JADE) as the Juno spacecraft arrived at Jupiter. JADE observations show that Juno crossed the bow shock at 08:16 UT on 2016 day of year (DOY) 176 and magnetopause at 21:20 on DOY 177, with additional magnetopause encounters until 23:39 on DOY 181. JADE made the first detailed observations of the plasma environment just inside the dawn flank of the magnetopause. We find subcorotational ions and variable electron beaming, with multiple flux tubes of varying plasma properties. Ion composition shows a dearth of heavy ions; protons dominate the plasma, with only intermittent, low fluxes of O+/S++, along with traces of O++and S+++. We also find very little H3+or He+, which are expected for an ionospheric plasma source. A few heavy ion bursts occur when the radial field nears reversal, but many other such reversals are not accompanied by heavy ions. First detailed plasma observations of the solar wind, bow shock, magnetopause, and outer dawn flank magnetosphere as Juno arrived at JupiterOuter dawn magnetosphere filled with flux tubes of varying plasma properties, counterstreaming electron beams, and sunward moving plasmaLack of heavy compared to light ions indicating difference from plasma disk and centrifugal separation along Jovian magnetic flux tubes
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- 2017
- Full Text
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47. Accelerated flows at Jupiter's magnetopause: Evidence for magnetic reconnection along the dawn flank
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Ebert, R. W., Allegrini, F., Bagenal, F., Bolton, S. J., Connerney, J. E. P., Clark, G., DiBraccio, G. A., Gershman, D. J., Kurth, W. S., Levin, S., Louarn, P., Mauk, B. H., McComas, D. J., Reno, M., Szalay, J. R., Thomsen, M. F., Valek, P., Weidner, S., and Wilson, R. J.
- Abstract
We report on plasma and magnetic field observations from Juno's Jovian Auroral Distributions Experiment and Magnetic Field Investigation at 18 magnetopause crossings when the spacecraft was located at ~6 h magnetic local time and 73–114 Jovian radii from Jupiter. Several crossings showed evidence of plasma energization, accelerated ion flows, and large magnetic shear angles, each representing a signature of magnetic reconnection. These signatures were observed for times when the magnetosphere was in both compressed and expanded states. We compared the flow change magnitudes to a simplified Walén relation and found ~60% of the events to be 110% or less of the predicted values. Close examination of two magnetopause encounters revealed characteristics of a rotational discontinuity and an open magnetopause. These observations provide compelling evidence that magnetic reconnection can occur at Jupiter's dawn magnetopause and should be incorporated into theories of solar wind coupling and outer magnetosphere dynamics at Jupiter. Observations at Jupiter's dawn magnetopause by Juno revealed accelerated ion flows and large magnetic shear angles at several crossingsCase studies of two magnetopause crossings showed evidence of rotational discontinuities and an open magnetopauseCompelling evidence for magnetic reconnection at the Jupiter's dawn magnetopause during Juno's approach to Jupiter and first capture orbit
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- 2017
- Full Text
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48. Comparison of methods for the reduction of reconstructed layers in atmospheric tomography
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Saxenhuber, Daniela, Auzinger, Günter, Louarn, Miska Le, and Helin, Tapio
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For the new generation of extremely large telescopes (ELTs), the computational effort for adaptive optics (AO) systems is demanding even for fast reconstruction algorithms. In wide-field AO, atmospheric tomography, i.e., the reconstruction of turbulent atmospheric layers from wavefront sensor data in several directions of view, is the crucial step for an overall reconstruction. Along with the number of deformable mirrors, wavefront sensors and their resolution, as well as the guide star separation, the number of reconstruction layers contributes significantly to the numerical effort. To reduce the computational cost, a sparse reconstruction profile which still yields good reconstruction quality is needed. In this paper, we analyze existing methods and present new approaches to determine optimal layer heights and turbulence weights for the tomographic reconstruction. Two classes of methods are discussed. On the one hand, we have compression methods that downsample a given input profile to fewer layers. Among other methods, a new compression method based on discrete optimization of collecting atmospheric layers to subgroups and the compression by means of conserving turbulence moments is presented. On the other hand, we take a look at a joint optimization of tomographic reconstruction and reconstruction profile during atmospheric tomography, which is independent of any a priori information on the underlying input profile. We analyze and study the qualitative performance of these methods for different input profiles and varying fields of view in an ELT-sized multi-object AO setting on the European Southern Observatory end-to-end simulation tool OCTOPUS.
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- 2017
49. Performance of lucerne genotypes for biomass production and nitrogen content differs in monoculture and in mixture with grasses and is partly predicted from traits recorded on isolated plants
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Maamouri, Amel, Louarn, Gaëtan, Béguier, Vincent, and Julier, Bernadette
- Abstract
Grass–legume mixtures are key crops to improve agricultural sustainability. Despite their significant use in mixture, lucerne (Medicago sativa L.) varieties are mostly tested and bred for monocultures. This study was performed to evaluate whether the ranking of lucerne genotypes for biomass components and quality was similar in monoculture and mixture, and whether traits recorded on isolated plants could help to predict performance in monoculture and mixture. For 46 genotypes planted in the three competition conditions, plant biomass, shoot height, shoot number and protein content were recorded. In addition, maximum leaf size, internode length, stem diameter, growth habit, specific leaf area and leaf dry-matter content were measured on isolated plants. A general positive correlation was observed between the performance of genotypes in monoculture and in mixture. However, significant changes in genotype ranking indicated that the species of its neighbours could modify the relative performance of a genotype. The traits that minimised competition intensity also changed according to the neighbour species. In mixture, competition intensity was highest for plants with long internodes, a high shoot number and a non-erect growth habit. In monoculture, plants with long internodes and larges leaves suffered less from competition. The agronomic performance of lucerne varieties differing in their architecture should be compared in monoculture and mixture to finally identify the traits to be phenotyped to improve lucerne variety performance in both cultivation modes.
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- 2017
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50. Making data sharing the norm in medical research
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Locher, Clara, Le Goff, Gérard, Le Louarn, Anne, Mansmann, Ulrich, and Naudet, Florian
- Published
- 2023
- Full Text
- View/download PDF
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