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[less ▲]Detailed reference viewed: 21 (1 ULiège) Origin and triggers of the 1-hour electron pulsations in the Saturnian systemPalmaerts, Benjamin ; Burkholder, B.; Delamere, P. A. et alConference (2019, June 07)Phenomena displaying a periodicity of around one hour have been frequently observed in Saturn's magnetosphere during the Cassini era. In particular, flux of energetic electrons can exhibit 1-hour quasi ... [more ▼]Phenomena displaying a periodicity of around one hour have been frequently observed in Saturn's magnetosphere during the Cassini era. In particular, flux of energetic electrons can exhibit 1-hour quasi-periodic pulsations. While these pulsations have been well characterized, their origin and the processes triggering them remained uncertain at the end of the Cassini mission. Using long imaging sequences of the auroral emissions at Saturn, we report the first direct observational evidence that the 1-hour periodicities arise from a global 1-hour oscillation of the Kronian magnetosphere. This natural oscillation acts independently of the local magnetospheric conditions and can have multiple triggering processes. Many 1-hour quasi-periodic electrons were encountered close to the magnetopause, suggesting that magnetopause processes could trigger them, such as magnetic reconnection and Kelvin-Helmholtz (KH) instabilities. We now report simultaneous presence of KH instabilities and 1-hour electron pulsations, supporting this scenario. Pulsed electrons are also encountered much deeper in the magnetosphere and may originate from reconnection in the magnetodisk, on both the day and night sides of the magnetosphere. [less ▲]Detailed reference viewed: 25 (6 ULiège) A nearly corotating long lasting auroral spiral at SaturnPalmaerts, Benjamin ; Yao, Zhonghua ; Sergis, N. et alPoster (2019, June 04)The main ultraviolet auroral emission at Saturn consists of multiple structures of various sizes forming a discontinuous ring of emissions around Saturn’s poles. For decades, it is known that the main ... [more ▼]The main ultraviolet auroral emission at Saturn consists of multiple structures of various sizes forming a discontinuous ring of emissions around Saturn’s poles. For decades, it is known that the main emission is occasionally organized in a global spiral surrounding the pole. In August 2016, the Ultraviolet Imaging Spectrograph (UVIS) on board the Cassini spacecraft proceeded to a 7h-long imaging of Saturn’s northern aurora. During this observing sequence, the main emission displayed a spiral wrapping around the pole by more than 370° in longitude. The spiral was in rotation around the pole at ~90% of rigid corotation, which is an unusually high velocity for extended auroral structures. A spiral was again observed during a shorter UVIS sequence, sixteen hours after the end of the first sequence. Simultaneously to the first UVIS sequence, imaging of the energetic neutral atom (ENA) emissions revealed a hot plasma population in the same local time sector as the extremity of the UV spiral. The leading edge of the plasma population follows the spiral structure around the planet. This correspondence suggests that the presence of the hot plasma distorted the magnetospheric current system, resulting in the spiral shape of the main emission. Furthermore, simultaneous in-situ measurements of the ion fluxes exhibit enhancements recurring every ~10.5 hours. The nearly corotating aurora, ENA emissions and ions revealed by this multi-instrument dataset are likely three signatures of a magnetosphere-ionosphere coupling current system and of the associated hot plasma population corotating with the planet. [less ▲]Detailed reference viewed: 36 (6 ULiège) Auroral diagnosis of solar wind interaction with Jupiter's magnetosphereYao, Zhonghua ; Bonfond, Bertrand ; Grodent, Denis et alPoster (2019, June)Detailed reference viewed: 22 (3 ULiège) Novel HST observations of the Galilean moons Io and Ganymede, and simultaneous Juno-UVS observations of the Io footprintRoth, Lorenz; Gladstone, G.R.; Hue, V et alConference (2019, June)Within two Hubble Space Telescope (HST) campaigns in support of the NASA Juno mission (GO14634 & GO15638, PI D. Grodent), spectra and spectral images of the moons Io and Ganymede were obtained by HST's ... [more ▼]Within two Hubble Space Telescope (HST) campaigns in support of the NASA Juno mission (GO14634 & GO15638, PI D. Grodent), spectra and spectral images of the moons Io and Ganymede were obtained by HST's Space Telescope Imaging Spectrograph (STIS) and Cosmic Origins Spectrograph (COS) on several occasions between 2017 and 2019. On one occasion around Juno's perijove #14 in July 2018, the Juno Ultraviolet Spectrograph (UVS) observed Io's footprint simultaneously to the HST imaging of Io. We compare the temporal variability of the local moon aurora and the footprint brightness. Through this comparison, we investigate how the amplitude and phase of the periodically changing brightness of Io's aurora and the footprint are correlated. Additionally, we present results from two novel far-UV observations of Ganymede: High- sensitivity spectra of the moon going into eclipse as well spectral images of the moon while transiting Jupiter. Both Ganymede observations are used to constrain the optical depth of the moon's atmosphere in the far-UV. [less ▲]Detailed reference viewed: 31 (2 ULiège) Electron pulsations generated by rotating magnetospheric dynamics at SaturnGuo, Ruilong ; Yao, Zhonghua ; Sergis, N et alPoster (2019, June)Quasi-periodic pulsations of energetic electrons have been frequently observed in Saturn's magnetosphere. The mechanisms for the electron pulsations are far from conclusive, although generally believed to ... [more ▼]Quasi-periodic pulsations of energetic electrons have been frequently observed in Saturn's magnetosphere. The mechanisms for the electron pulsations are far from conclusive, although generally believed to be associated with field-line resonance due to their similar periodicities. Here we report an electron pulsation event that is related to aurora beads and energetic neutral atom (ENA) emissions. The perturbation of the magnetic field indicates that Cassini spacecraft encountered a series of field-aligned currents (FACs) connected to the aurora beads. The fluxes of energetic electrons were enhanced when the spacecraft crossed the FACs. Both aurora beads and ENA emission were rotating. Given that the FACs interconnect the aurora beads and the active region at equator, a hot plasma population associated with the ENA enhancement, we conclude that the FACs were rotating with Saturn and had finite extent in the azimuthal direction. The periodic features also manifested in the whistler-mode auroral hiss emissions in the same event. We proposed that the electron pulsations we studied are spatial effect of the rotating magnetosphere. The rotation of the whole magnetosphere transfers the spatial effect to the temporal effect, i.e., the pulsation sequences observed by Cassinis multiple instruments. [less ▲]Detailed reference viewed: 45 (4 ULiège) Simultaneous Hubble Space Telescope and Juno observations of a jovian auroral enhancement eventNichols, J.D.; Allegrini, F.; Bagenal, F. et alConference (2019, June)We present concurrent observations of Jupiter's auroras obtained with the Hubble Space Telescope and the planets magnetodisc and M-I coupling currents as observed by the Juno spacecraft, indicating an ... [more ▼]We present concurrent observations of Jupiter's auroras obtained with the Hubble Space Telescope and the planets magnetodisc and M-I coupling currents as observed by the Juno spacecraft, indicating an association of Jupiter's auroral intensity with current intensity. During PJ11 inbound, Juno measured in the middle magnetosphere a substantial increase in $B_\phi$ from a ‘nominal background of ~2 nT to 7-9 nT between ~30 and 55 R_J, implying increased equatorial radial current flowing as part of the M-I coupling current system associated with the planets auroral emission. During this interval, the $B_\rho$ component was also enhanced from ~10 to ~20 nT, indicating increased azimuthal current and associated radial force balance in the magnetodisc. During this interval of increased radial current, the Hubble Space Telescope observed a simultaneous enhanced intensity of the main emission, peaking at ~2 MR. We compare these observations with the Leicester magnetodisc model, referenced to preliminary Juno JADE plasma data, and the associated theoretical M-I coupling currents. [less ▲]Detailed reference viewed: 28 (1 ULiège) Observation of auroral “raindrops” in Jupiter's polar region by Juno-UVSHue, Vincent; Greathouse, T.K.; Gladstone, Randy et alConference (2019, June)Juno-UVS has observed Jupiter's FUV auroral emissions during 19 close flybys following Juno orbital insertion on 5 July 2016. Each perijove provides a different snapshot of the Jovian auroral emissions ... [more ▼]Juno-UVS has observed Jupiter's FUV auroral emissions during 19 close flybys following Juno orbital insertion on 5 July 2016. Each perijove provides a different snapshot of the Jovian auroral emissions recorded at different system III longitude and local time conditions. During PJ6 (19 May 2017), UVS recorded several transient auroral features located within Jupiter's northern polar auroral region. These auroral “raindrops” are characterized by bright spots of H2 emission (typically ~100 kR), which expand into concentric circles over tens of seconds, and seem to appear most often at local times close to noon. In this study we characterize where the raindrops occur in Jupiter's polar region, their spectral characteristics, and their typical expansion rates. [less ▲]Detailed reference viewed: 23 (1 ULiège) Are Dawn Storms Jupiter's auroral Substorms?Bonfond, Bertrand ; Yao, Zhonghua ; Gladstone, R. G. et alPoster (2019, June)There are multiple evidences that mass and energy rarely circulate smoothly in planetary magnetospheres. To the contrary, these systems tend to accumulate them until they fall out of balance through ... [more ▼]There are multiple evidences that mass and energy rarely circulate smoothly in planetary magnetospheres. To the contrary, these systems tend to accumulate them until they fall out of balance through reconfiguration events. The source of mass and the source of energy can differ, as well as the trigger that initiates the collapse. However, despite some fundamental differences between the planets, the auroral signatures of the global reconfigurations bear many similarities that inform us on the common physical processes at play. For the first time, Juno has granted us a complete and global picture of one type of such reconfigurations, the auroral dawn storms, from their initiation to their vanishing. Juno actually captured views of dawn storms at different stages of development in approximately half of the cases. For example, on PJ11 and PJ16, Juno-UVS caught the brief appearence of small elongated spots located poleward of the main emission in the midnight sector. In both cases, a few hours later, the main emission began to brighten and broaden in the same sector. Then the main arc split into two parts, one moving towards the pole and the other moving equatorward. The whole feature also started to rotate towards the dawn sector, progressively accelerating to co-rotation. On PJ6, Juno-UVS observations missed the beginning of the event, but they allowed us to examine the next phase. After the broadening and the splitting of the main emission, the outer arc transformed unto large blobs. During the same time interval, subsequent Hubble Space Telescope images confirmed that the blobs kept on evolving, forming latitudinally extended fingers. All these auroral features resemble auroral morphologies observed at Earth during substorms. The Jovian elongated spots look like terrestrial poleward boundary intensifications (PBIs), the poleward motion of the arc indicates a dipolarisation/current disruption and the blobs in the outer emissions suggest massive plasma injections. [less ▲]Detailed reference viewed: 39 (6 ULiège) A study of Local Time Variations of Jupiter’s Ultraviolet Aurora using Juno UVSGreathouse, T.K.; Gladstone, G.R.; Verteeg, M.H. et alPoster (2019, June)With 19 successfully completed Perijoves, Juno UVS has collected an enormous amount of data with unprecedented views of the northern and southern auroras spanning all local time geometries. Juno UVS, with ... [more ▼]With 19 successfully completed Perijoves, Juno UVS has collected an enormous amount of data with unprecedented views of the northern and southern auroras spanning all local time geometries. Juno UVS, with its spectral and spatial mapping capabilities allows for the retrieval of both UV brightness as well as color ratio information. Maps of both the brightness and color ratio of the main ovals and polar emissions display strong local time variations, some suggestive of ionospheric local time control while others magnetosphere local time drivers. In this presentation we bring together all the UVS observations to date to show and catalogue the many local time phenomena evident therein. [less ▲]Detailed reference viewed: 25 (3 ULiège)