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1 - Radio occultations of the Io plasma torus with the Juno spacecraft: A study of feasibility
Phillip H. Phipps, Paul Withers
Volcanoes on the innermost Galilean satellite, Io, release material into the surrounding area in Jupiter’s magnetosphere where it is subsequently ionized. The material becomes trapped in Jupiter’s magnetic field and distributed into a torus around Jupiter, called the Io plasma torus. On each perijove of the Juno spacecraft the line of sight between Juno and the Earth passes through the Io plasma torus. We show that a radio occultation will occur during the perijove pass of the spacecraft. It is also show that the effect on the radio signal passing through the Io plasma torus can be used to determine the torus total electron content, assuming 36 second integration times. From the total electron content we find that Io plasma torus parameters can be determined with 10 % uncertainties.
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2 - Radio emission from the Ganymede-Jupiter interaction and consequence for radio emissions from exoplanets
Philippe Zarka, Manilo Soares-Marques, Corentin Louis, Vladimir Ryabov, Laurent Lamy, Ezequiel Echer , Baptiste Cecconi, Sébastien Hess, Andrée Coffre, Laurent Denis
Analysis of a catalog of 26 years of radio decameter observations from Jupiter in Nançay (France) allowed us to detect unambiguously the radio emissions resulting from the Ganymede-Jupiter interaction. The duration and power of the 189 events detected suggest sporadic reconnection with an average radio power released in the Ganymede-Jupiter decameter emission 15 times smaller than in the Io-Jupiter one. This compares well with the ratio of the magnetic power (Poynting flux) dissipated at the Ganymede-Jupiter and Io-Jupiter interactions, confirming the radio-magnetic Bode's law of Zarka et al. (2001), that serves as a basis for predicting exoplanetary radio emissions. Constraints imposed by the Ganymede-Jupiter radio emission on Jovian magnetic field models are also discussed.
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3 - Detection of Jupiter decametric emissions controlled by Europa and Ganymede with Voyager/PRA and Cassini/RPWS
C. K. Louis, L. Lamy, P. Zarka, B. Cecconi, and S. L. G. Hess
The Jovian high latitude radio emissions produced by Jupiter's magnetosphere extend from a few kHz to 40 MHz. Part of the decametric emissions are not auroral but driven by the Galilean moon Io (Io-DAM), and we expect the other Galilean moons Europa, Ganymede and Callisto to drive jovian radio emissions too. Indeed UV emissions induced by those three first Galilean moons exist. We used a simulation code named ExPRES (Exoplanetary and Planetary Radio Emissions Simulator) to predict dynamic spectra (time-frequency spectograms) for the radio emissions controlled by the four Galilean moons. Then we compared the simulations to the Voyager (PRA instrument) and Cassini (RPWS instrument) data acquired during their flybys of Jupiter (in 1979, and between 2000 and 2003, respectively). We detected Jupiter DAM emissions controlled by Europa (130 events) and Ganymede (96 events). The statistical analysis of those detections allows us to describe the average properties of the Europa-DAM and Ganymede-DAM emissions (spectral, temporal variability, occurrence in a diagram satellite phase versus central meridian longitude).
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4 - A new physical model of the electron radiation belts of Jupiter inside Europa’s orbit: on the key role of the plasma waves above the orbit of Io
Quentin Nénon, Angélica Sicard, Sébastien Bourdarie
From 1998 to 2004, ONERA has adapted its 3D physical model of the Earth radiation belts, Salammbo, to the Jovian electron belts. An upgraded Jupiter-Salammbo model that extends from the Jovian surface to the orbit of Europa will be presented. The model now takes into account the gyro-resonant interaction with the plasma waves detected by Galileo above the orbit of Io. It also now relies on a realistic outer boundary condition (i.e. electron injection near Europa), well constrained by the in-situ flux measurements and consistent with the empirical models.
The validation of Salammbo against in-situ and remote (synchrotron emission) observations will be discussed, as the key role of the plasma waves in the Jovian electron belts.
Finally, the benefits of developing a physical model of the trapped protons to further constrain the physical processes shaping the electron belts, in particular the radial diffusion and sweeping effects by the moons and dust rings, will be pointed out.
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5 - An updated physical model of the proton radiation belts of Jupiter inside Europa’s orbit
Angélica Sicard, Quentin Nénon
In 2004, ONERA has developed a 3D physical proton model of the Jovian radiation belts, Salammbo, inside Io orbit. An updated Jupiter-Salammbo proton model that extends from the Jovian surface to the orbit of Europa will be presented. The model takes into account the major physical processes governing the Jovian radiation belts: radial diffusion, interaction with moons and rings, charge exchange, interaction with cold plasma…. The relative importance of each physical process will be investigated. It also now relies on a realistic outer boundary condition near Europa, well constrained by the in-situ flux measurements (Galileo, Voyager, Pioneer) and consistent with the empirical models. The validation of this updated Salammbo proton model against in-situ measurements will be discussed.
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6 - The Jovian Current Sheet as Observed by Juno’s JADE
R.J. Wilson, F. Bagenal, P.W. Valek, D.J. McComas, S.J. Bolton, F. Allegrini, N.G. Angold, J.e.p. Connerney, K. Chae, R.W. Ebert, T.K. Kim, S. Levin, C.E. Loeffler, P. Louarn, D.A. Ranquist, M. Reno, J.R. Szalay, M.F. Thomsen, S. Weidner, J.L. Zink
The Juno spacecraft is on a polar orbit around Jupiter, where the inbound trajectory to each perijove (PJ) is closer to equatorial regions than the outbound. The JADE suite of sensors on Juno measures the thermal plasma (0.1 to 100 keV/q for electrons and 0.01 to 50 keV/q for ions) and was only on around perijove for PJ1 to PJ3. For the first time, at PJ4, JADE turned on and stayed on for the entire orbit. During 2017-082 to 2017-085 (inbound towards PJ5, which is 2017-086) multiple current sheet crossing were observed where both the protons and heavy ions (O^{n+} and S^{n+}) were within the JADE energy range. Ion counts are few when JADE was outside the current sheet (and predominantly protons, but plausible that heavier ions are above JADE’s energy range). However, during current sheet encounters the heavy ions dominate the denser plasma. We investigate the plasma properties of these initial JADE observed current sheet encounters.
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7 - Statistical analyses of Jovian Io and non-Io decametric emissions using the new Nancay 26-year catalog
E. Echer, M. S. Marques, P. Zarka, V. B Ryabov, M. V. Alves, L. Denis, A. Coffre
Recently a catalog of Nançay Decametric Array observations of Jovian radio emissions has been compiled. The catalog is based on digital data from 1990 to 2015. Jovian decametric (DAM) emissions have been classified in Io and non emission types, and in the different sources (“A”, “B”, “C”, “D”). In this work, statistical analyses of these emissions are presented. Emission occurrence rate, duration, maximum frequency and polarization are analysed. Further, new emission types have been classified (Io-A”, Io-B’ and non-Io-D). The results obtained with this new catalog can be used for a large number of studies of Jupiter’s magnetosphere, such as long-term variations, solar wind-Jupiter magnetosphere coupling, cooperative studies with spacecraft (e.g, Galileo, Cassini flyby, Juno) and other observations and models.
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8 - Variations of Jupiter's auroral radio emission in relation to magnetospheric plasma enhancement event
Hiroaki Misawa and Fuminori Tsuchiya
Around Jupiter's oppositions to the earth after 2014, remote observations for Jupiter had been made continuously by the Japanese space telescope satellite HISAKI in the UV range. In particular in the 2015 campaign period, sudden enhancement of Iogenic plasma emissions occurred in the middle of Jan. and the enhancement had lasted for more than two months. This interesting phenomenon would give a valuable opportunity to study what elements and/or processes affect magnetosphere's variations.
We have investigated occurrence features of Jupiter's auroral radio emissions in the hectometric and decametric wave ranges (HOM and DAM, respectively) and have examined their relations with the Iogenic plasma variations using the WIND/WAVES radio wave data. From the analysis, it is found that the both radio emissions showed following characteristic variations; occurrence probability/intensity of HOM has increased, and the recurrence periodicity of non Io-DAM's "QP burst" (Panchenko et al., GRL, 2010; PSS, 2013) has been shorter during the plasma enhance period. This result in HOM is opposite to the precedent study by Yoneda et al. (GRL, 2010). As for the result in DAM, variation of the recurrency for the particular period is a new aspect in this “QP” burst.
In the presentation, we will introduce the variation features in HOM and DAM precisely, and would like to discuss expected source region and processes driving these characteristic radio wave variations.
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9 - Energetic ions and electrons inward of Jupiter's rings from Juno/JEDI
P. Kollmann, C. Paranicas, G. Clark, A. M. Rymer, B. H. Mauk, D.K. Haggerty, L. Brown, J. Peachey, D. Santos-Costa, J. Saur., J. E. P. Connerney, F. Allegrini, P. Valek, W. S. Kurth, G. R. Gladstone, S. Levin, S. Bolton
Juno is the first spacecraft that repeatedly passes close to Jupiter’s surface. Its closest approach distances are around 1.06RJ from Jupiter’s center. Juno’s orbit makes it uniquely suited to study the innermost region of Jupiter’s magnetosphere, including a region that magnetically connects near the rings. The JEDI instrument we use measures charged particles in the keV to MeV range and distinguishes ion species.Already Juno’s first science pass revealed the existence of an ion population inward and throughout Jupiter’s rings. The energy spectrum is rising at hundreds of keV, which is consistent with the ions being supplied by energetic neutral atoms that are produced in the Io & Europa neutral cloud and stripped in Jupiter’s high atmosphere. This seems to be a common process since it is also thought to occur at Earth and Saturn.
The innermost ion belt is time or longitude dependent, since it is not seen in all of Juno’s passes. In the absence of ions, an electron population can be measured. While there can be ambiguity in the JEDI data between the detection of electrons and ions, we confirm that these measurements are dominated by electrons. Electrons were previously measured throughout the magnetosphere to have a spectrum that rolls over in the MeV range. The electron spectra near Jupiter show a similar shape but roll over in the hundreds of keV range, indicating that their origin and history differs.
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10 - H/H2 Brightness Ratio of Jupiter Aurora
Chihiro Tao, Laurent Lamy, Renée Prangé, Nicolas André, Sarah V. Badman
The far-ultraviolet (FUV) aurora seen on giant planets is directly produced by the precipitating auroral electrons. An analysis of Saturn’s aurorae taken by the Ultraviolet Imaging Spectrograph instrument onboard the Cassini spacecraft showed that the brightness ratio of H Lyman-α to H2 auroral emissions statistically decreases with the brightness of H2 taken as a proxy of the energy of precipitating electrons. This ratio is suggested to provide a sensitive diagnosis of auroral electron energy from modeling studies, and the measurement was then investigated in details for the Saturn’s case to show that the brightness ratio provides low energy electrons (typically lower than 10 keV), in contrast with the FUV color ratio (CR) method which provides the energy of electrons >10 keV. The H/H2 ratio would be also useful for the Jupiter case to investigate the role of low energy auroral electrons, and we investigated the relationship of Jupiter auroral observed by the Hubble Space Telescope. The H/H2 brightness ratio does not show any clear relationship with the FUV CR which is sensitive to more energetic electrons. Compared to the same analysis applied for Saturn aurora, we found that the relationship for Jupiter mainly shows decreasing flux with increasing energy without acceleration features, which would reflect the different plasma environments.
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11 - Studying Jupiter’s X-ray aurora with Chandra
Caitriona Jackman, Will Dunn, Ralph Kraft, Randy Gladstone, Graziella Branduardi-Raymont
The Chandra space telescope has recently conducted a number of campaigns to observe Jupiter’s X-ray aurora. We report on results from two of these campaigns. The first campaign took place in summer 2016 while the Juno spacecraft was upstream of the planet sampling the solar wind, and the second campaign covers spring and summer 2017, with Chandra observations matched to the times when Juno was at apojove and predicted to be near the dawn flank magnetopause. We report on the X-ray observations including intensities and periodicities of auroral X-ray emissions. We aim to examine possible drivers of X-ray emission including reconnection and the Kelvin-Helmholtz instability and to explore the role of the solar wind in controlling the emissions.
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12 - Juno/JEDI observations of energetic ion precipitation in the Jovian auroral region
D. K. Haggerty, B. H. Mauk, C. Paranicas, G. Clark, P. Kollmann, A. M. Rymer, S. J. Bolton, J. E. P. Connerney, S. M. Levin.
The Juno spacecraft’s polar orbit provides an exceptional opportunity to study auroral processes in the largest and most dynamic auroral region in the solar system. The Jupiter Energetic particle Detector Instruments (JEDI) have SSD telescopes with multiple look directions and additional time-of-flight capabilities to measure ions and electrons from ~ 6 keV to ~20 MeV. These instruments resolve major ion species beginning at ~30 keV/n, with coarser mass resolution for lower energy ions. JEDI instruments observed energetic heavy ions up to 20 MeV precipitating into the auroral regions during the first few Juno perijoves that have occurred to date, but the intensity and spatial location vary greatly from one pass to the next. Precipitating energetic heavy ions are believed to be the source population for Jupiter’s x-ray aurora. We report on the new findings of energetic heavy ions from the first few Juno orbits with an emphasis on the auroral regions. We will also compare and contrast the observations from each of the auroral passes.
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13 - The spatial distribution of atomic oxygen emission at 130.4 nm around Io's orbit observed by Hisaki/EXCEED.
Ryoichi Koga, Fuminori Tsuchiya, Masato kagitani, Takeshi Sakanoi, Mizuki Yoneda, Kazuo Yoshioka, Tomiki Kimura, Ichiro Yoshikawa, Atsushi Yamazaki, Go Murakami, Smith, H. Todd
The atmosphere of a Jovian satellite Io has been thought to be mainly by volcanism and sublimation of frost. Dominant atmospheric gases are sulfur dioxide, and dissociative product such as atomic oxygen and sulfur, which are produced mainly by electron impact dissociation and photolysis. Neutral oxygen escape from exobase to neutral clouds (> 5.8 Io radius) mainly by atmospheric sputtering. However, it was not understood the characteristics of spatial distribution of atomic oxygen escaping from Io.
we investigated Io phase angle (IPA) dependence of atomic oxygen emission at 130.4 nm averaged for the distance range of 4.5-6.5 Jupiter radius from Jupiter in the dawn and dusk sides, respectively during volcanically quiet period (DOY -35 -1). Then, we found following two important observation fact. First, weak atomic oxygen emission (4-6 Rayleighs (R)) continuously exists on both dawn and dusk sides not depending on the phase angle. This suggests that small amount of atomic oxygen distributes uniformly along the Io’s orbit. Second, the emission averaged between IPA 60-90 degrees (14.0 R) was larger than that between IPA 90-120 degrees (10.5 R) on the dawn side, there was a similar tendency on the dusk side. We can explain this difference if the large amount of atomic oxygen spread inward and ahead of Io’s orbit and shape like banana expected by the model of atomic oxygen neutral clouds such as Smyth and Marconi [2003].
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14 - Kinetic Alfven wave propagation and electron trapping in the Io plasma torus
P.A Damiano, B. Stauffer, P.A. Delamere, and J.R. Johnson
Electron energization by dispersive Alfven waves (either inertial or kinetic) is associated with Alfvenic aurora in the terrestrial magnetosphere and is assumed to play a role at Jupiter as well since Io's interaction with the Jupiter magnetosphere is a large source of Alfven wave energy. In the terrestrial plasma sheet, the kinetic Alfven wave (KAW) regime dominates and electrons with speeds close to the phase speed of the wave can resonantly interact with the wave and become trapped in the wave potential. This trapping leads to an elongated core to the electron distribution function parallel to the background magnetic field that is evident in both observations and simulations. The Io plasma torus is also a region where KAWs are thought to be prevalent and where important differences, from the terrestrial example, include the dominance of heavy ions and the trapping of wave energy in the steep density gradients at the torus boundaries. In this presentation, we summarize and compare efforts to study KAW propagation in the torus using both traditional hybrid (kinetic ion, fluid electron) and gyrofluid kinetic-electron models. Using the latter, we also address electron trapping in the KAWs and find that trapping within the wave increases with ion mass and we track the evolution of the trapped electron population as the wave propagates through the steep density gradients at the torus boundary.
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15 - The Juno Investigation of Jupiter's Magnetosphere: Orbit and Science
B.A. Bolton, I.e.p. Connerney
The Juno Investigation of Jupiter's Magnetosphere: Orbit and Science
B.A. Bolton (1) and I.E.P. Connerney (2,3)
1. Artistic Sciences, Inc., San Antonio, TX, USA
2. Space Research Corporation, Annapolis, MD, USA
3. Technical University of Denmark (DTU), Lyngby, Denmark
Juno is the first mission to investigate Jupiter using a close polar
orbit. The Juno science goals include the study of Jupiter's polar
magnetosphere, interior structure, deep atmosphere and composition. An
overview of Juno's magnetospheric investigation and how the orbit explores
Jupiter's polar and distant magnetosphere will be presented. Interesting
and key target regions are identified as they relate to Juno results presented
in other poster papers to facilitate comparison and analysis discussions.
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16 - Jupiter’s Plasma Sheet and Io Torus: Voyager, Galileo, Cassini, Hisaki, Juno
Fran Bagenal
Each mission provides a unique perspective. The Voyager flybys of Jupiter in 1979 provided a key first good look at the Io plasma torus and plasma sheet that had only been hinted at from the ground and Pioneer. Cassini gained its gravity to assist to Saturn by passing far from Jupiter but provided the first high definition measurements of the Io plasma torus UV emissions. Analysis of these emissions honed the tools for modeling the physical chemistry of the torus plasma. While hampered by a damaged antenna, Galileo’s seven years at Jupiter monitored temporal variability of the system. From Earth orbit, the Hisaki satellite has been observing the Io plasma torus since 2013. By MOP, Juno will have passed five times through the system at high latitudes. In this paper we review the observations of Voyager, Cassini and Galileo of the Io plasma torus and jovian plasma sheet (in the light of current understanding) and consider the new in-sights provided by Hisaki and Juno.
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17 - Linking High Latitude Ion Observations to Equatorial Sources at Jupiter
J. R. Szalay, F. Allegrini, F. Bagenal, S. Bolton, G. Clark, J. E. P. Connerney, R. W. Ebert, D. J. Gershman, W. S. Kurth, S. Levin, P. Louarn, B. Mauk, D. J. McComas, C. Paranicas, D. Ranquist, M. Reno, M. F. Thomsen, P. W. Valek, S. Weidner, R. J. Wilson
Plasma measurements provide some of the most critical information we have about Jupiter’s magnetospheric structure and dynamics. The Juno mission carries the Jovian Auroral Distributions Experiment (JADE), which detects low energy ions (<50 keV/q) and electrons (<100 keV). JADE observed high latitude proton, oxygen, and sulfur populations when magnetically connected to the Io torus and inner/middle plasma sheet. Both the proton and heavy ion temperatures are observed to increase with increasing equatorial magnetic mapping distances from ~5 jovian radii up to a plateau after 15-20 jovian radii. These populations are observed to have a high degree of variability, exhibiting 1-2 orders of magnitude differences in high latitude energy fluxes for similarly mapped observations across multiple Juno orbits. However, since there are uncertainties in both the internal field models and the correct field line mapping to the equator, these variations should be considered with those factors in mind. In this study, we examine these high latitude ion distributions in the context of their plasma sheet source distributions and compare the diversity of measurements taken by JADE amongst Juno’s multiple close approaches.
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18 - The Search for the Kelvin-Helmholtz Instability on Jupiter’s Dawn Side Magnetopause using Juno
Drake Ranquist, Fran Bagenal, Stefan Eriksson, Rob Wilson, George Hospodarsky, Daniel Gershman, John Connerney, William Kurth, Philip Valek, Barry Mauk, Peter Delamere
Juno’s 53-day orbit spends substantial time at Jupiter’s magnetopause boundary. Over the first several orbits, Juno’s instruments have detected dozens of magnetopause crossings. Masters et al. (2012) found surface waves at Saturn’s magnetopause by determining the boundary normal orientation of each of Cassini’s crossings of the magnetopause. Similarly, we search for surface waves on Jupiter’s magnetopause by using minimum variance analysis (MVA) on the magnetic field data provided by the Juno Magnetic Field Investigation (MAG). Juno’s orbit is on Jupiter’s dawn side, where magnetospheric corotation is in the opposite direction to magnetosheath flow, which encourages the growth of the Kelvin-Helmholtz Instability (KHI). KHI, in turn, can lead to mixing of magnetospheric and magnetosheath plasma and magnetic reconnection. Here we present the results of this study.
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19 - The Commissioning of the Io Input/Output Facility (IoIO), a robotic observatory for studying Jupiter's magnetospheric response to Io's volcanic activity
Jeff Morgenthaler, Julie Rathbun
We have recently constructed the Io Input/Output (IoIO) facility, a small-aperture ground-based robotic observatory which will conduct nightly observations of the Io plasma torus (IPT) and the Jovian sodium nebula for the next 5 Jovian oppositions. IoIO measures the brightness and morphology of the Jovian sodium nebula to ~50 Rj and the brightness and positions of the IPT ansas. The brightness of the Na nebula, together with Io IR observations contemporaneously recorded at NASA's IRTF, provide a measure of the amount of material flowing into the IPT. The brightness of the IPT ansas indicates how much material is impounded there. The east-west shift of the IPT ansas provides a measure of the amount of material flowing toward the magnetotail. We will use the relative timings of the peaks in the IPT brightness and IPT shift to determine whether or not physical processes originating in the magnetotail drive mass loss from the IPT.
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20 - What impedes radial transport of material in Jupiter's inner magnetosphere?
Jeff Morgenthaler (Planetary Science Institute), Max Marconi (Prisma Basic Research)
The Io plasma torus (IPT) is a collection of ions trapped in Jupiter's magnetic field near Io's orbital radius. Based on estimates and modeling of the interchange instability, the residence time of IPT ions should be ~10 hours. The observed residence times are 20 -- 80 days. What physical mechanism is impeding radial diffusion from the IPT? Two ideas have been proposed: (1) velocity sheer impoundment of flux tube interchange and (2) ring current impoundment. In support of (2), Louarn et al. (2014) find a coincidence between Galileo observations of particle injection events, Jovian hectometric emission (HOM), and narrow-band kilometric radiation (nKOM) and propose that reconnection/reconfiguration events in the magnetotail send particle injections inward, triggering HOM. The particles erode the ring current and let IPT material leak out, triggering nKOM. We present new analyses of spectroscopic observations of Io's exospheric oxygen emission which effectively turn Io into an in situ plasma probe. Using the Smyth & Marconi semi-empirical IPT model, we show evidence of missing mass in the plasma torus in the post midnight sector during a Louarn et al. event, providing independent corroboration of the Louarn et al. picture of mass loss from the IPT and therefore the ring current impoundment mechanism.
This work is supported by NASA Outer Planets Research grants NNX11AM43G and NNX13AL08G to the Planetary Science Institute.
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21 - Image processing of ground based observations of [SII] emission lines from the Io plasma torus
Fabiola Pinho Magalhaes, Walter Gonzalez, Ezequiel Echer, Mariza Pereira Echer, Jeff Morgenthaler, Rosaly Lopes
Immersed in Jupiter's magnetosphere is Io, the innermost of the Jupiter’s four Galilean moons. Io is a remarkable object due to its intense volcanic activity. Io's volcanism produces a tenuous atmosphere that escapes creating the Io plasma torus (IPT), a ring of charged particles encircling Jupiter. Considering this scenario, it is reasonable to expect that the IPT torus should be affected by changes in Io's volcanism. Observations of the Jovian satellites from space-based platforms began in the early 1970s with the launch of Pioneer 10 and 11. Since then several encounters occurred with Jupiter and the Galilean satellites. Ulysses, Cassini and New Horizons took information at a distance, while Galileo had made several flybys on Io. However an outstanding question concerning the complex Io-Jupiter coupled system is how Io's volcanic activity affects the IPT variability. In this work, it is focused on [SII] 6731 Å emission lines from the IPT, obtained by ground-based observations at the MacMath-Pierce Solar Telescope in the late nineties. Here is presented the methodology developed to image/data processing of the torus and some first anlaysis of the intensity variatbility, with the aim to obtain information related to system IV.
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22 - Juno Bow Shock and Magnetopause Encounters at Jupiter
G. B. Hospodarsky, W. S. Kurth, S. J. Bolton, F. Allegrini, G. B. Clark, J. E. P. Connerney, R. W. Ebert, D. K. Haggerty, S. Levin, D. J. McComas, C. Paranicas, A. M. Rymer, P. W. Valek and C. Tao
The Juno spacecraft has crossed Jupiter's bow shock (BS) and magnetopause (MP) multiple times in the dawn sector (near 0600 Local Time), both during the approach to Jupiter and during the first five apojove periods. A survey of all of these crossings using the Juno field and particle instruments has been performed, with over 50 bow shock and 100 magnetopause crossings being detected. The BS crossings ranged from 92 to 128 RJ and the MP crossings ranged from 73 to 114 RJ. During approach, Juno initially encountered an expanding magnetosphere resulting in a single BS and MP crossing, followed a few days later by a contracting magnetosphere, resulting in seven more MP crossings and a BS crossing on the first outbound orbit at 92 RJ. The lack of BS crossings and the limited number of MP crossings during the second apojove period suggests a long period of an expanded magnetosphere, likely caused by a prolonged period of low solar wind dynamic pressure associated with a rarefaction region. Juno's encounters with these boundaries, and their apparent motion (inward or outward) will be compared to models and predictions of the shape of the Jovian magnetosphere. Solar wind propagation models will also be examined for possible correlations between the encountered boundaries and solar wind dynamics.
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23 - Enhancing Jupiter's Auroral Second Oval
Rebecca Gray, Sarah Badman, Emma Woodfield, Chihiro Tao
The second oval is a feature of the Jovian outer auroral emission seen as sections of discrete arcs of varying length, equatorward of the main auroral oval. This study quantifies the location and intensification of the second oval feature during sequences of images taken by the Hubble Space Telescope. Small sections of the feature can be picked out in most images, however the feature appears brighter and extended longitudinally 1-3 days after large injection signatures. The feature lies close to the latitude of the Ganymede auroral footprint. We complement the image analysis with spectral analysis of the injection and second oval signatures as well as theoretical consideration of wave-particle interactions as a possible generation mechanism. The study is particularly timely given recent JUNO JEDI and Waves results, describing where energetic particles occur and waves may grow in the Jovian magnetosphere, in addition to UVS results, describing the aurora at all longitudes.
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24 - Characteristics of temporal variations in IPT and auroral emissions deduced by EXCEED
Fumiharu Suzuki, Kazuo Yoshioka, Go murakami, Fuminori Tsuchiya, Tomoki Kimura, and Ichiro Yoshikawa
Jovian magnetosphere is characterized by its strong magnetic field and plasma supply by Io. It is an “internally-driven” magnetosphere with superior co-rotation compared with the solar wind. In the inner side of the Jovian magnetosphere, there is an energetically significant structure called Io plasma torus (IPT), which can be an index of the density of hot plasma. It is pointed out that auroral brightennings are correlated with the phenomenon in the middle and outer magnetosphere which is magnetically connected to the planet’s pole regions.
Previous study using EXCEED onboard the Hisaki spacecraft detected the phenomenon that IPT brightens in response to auroral brightenings. This suggests the existence of inward energy flow from the middle magnetosphere to the inner magnetosphere. However, it was just the discovery of several events, and statistical analysis was not done. Therefore, features of brightenings were not clarified.
Thanks to the long-term and continuous observation for aurora and IPT by EXCEED, we identified dozens of brightening events, and statistically investigated the features of the brightenings. It became clear that local time dependence exists in the IPT brightenings. In addition, it was found that different type of such IPT brightening events occurred in Io's volcanic active period. This suggests the existence of multiple energy transport mechanisms between the inner and middle magnetosphere.
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25 - Variation of ion and electron temperature on Io plasma torus during an outburst measured with Hisaki/EXCEED and gourd-based telescope
Masato Kagitani, Mizuki Yoneda, Ryoichi Koga, Fuminori Tsuchiya, Kazuo Yoshioka, Go Murakami, Tomoki Kimura, Ichiro Yoshikawa
We focus on variability of electron temperature on Io plasma torus (IPT) derived from EUV diagnostics measured by space telescope Hisaki/EXCEED after a volcanic outburst in 2015, as well as ion temperatures parallel and perpendicular to the magnetic field measured from the ground-based spectroscopy. The [SII] observation of IPT was made at Haleakala Observatory from November 2014 through May 2015 with the Echelle spectrograph (R=67,000) coupled to a 40-cm telescope, which enables to enables to measure S+ temperatures parallel and perpendicular to the magnetic field. We also made observation of neutral sodium cloud as a proxy of supply of neutral particles from Io (Yoneda et al., 2015). Based on observation of neutral sodium cloud (Yoneda et al., 2015), neutral supply started to increase at around DOY= 10, was at maximum at around DOY = 50, and has backed into the initial levels at around DOY = 120. In contrast, plasma diagnostics made by Hisaki/EXCEED EUV spectroscopy indicates that hot electron fraction was less than 2 % before DOY = 50, started to increase after DOY = 50, and have reached 8(+/-1) % at DOY = 110. In addition, ion temperatures from ground-based observation started to increase after DOY=50 as similar tread of increase of hot electron fraction. Aurora sudden brightening events were also activated after DOY = 50 as increase of hot electron fraction on the plasma torus. A possible scenario will be discussed on the presentation.
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26 - Ion compositions in Jupiter's magnetosphere observed by Juno JADE-I
Thomas K. Kim, P. W. Valek, D. J. McComas, F. Allegrini, N. G. Angold, F. Bagenal, S. J. Bolton, K. Chae, C. Loeffler, R. W. Ebert, S. Levin, P. Louarn, C. Pollock, D. A. Ranquist, J. R. Szalay, M. L. Reno, M. F. Thomsen, S. Weidner, R. J. Wilson, J. L. Zink
The Jovian Auroral Distributions Experiment Ion sensor (JADE-I) is a plasma instrument on Juno that can measure ions with energies ranging from 0.01 – 46.2 keV/q for individual ion species. However, ion species with similar mass per charge (M/Q) can create an ambiguity in determining the measured ion species.
Magnetospheric plasmas at Jupiter are mostly composed of dissociation products of iogenic SO2, which include ion species with similar M/Q (e.g., O+ and S2+ both have M/Q of ~16 amu/q). These ions, so called iogenic plasmas, were first observed by plasma instruments onboard previous missions (e.g., Voyager 1 and 2, Galileo, etc.). However, the relative abundance of O+ and S2+ in Jupiter’s magnetosphere were only studied using physical assumptions due to the inability of the instruments to resolve the O+ and S2+.
Thin carbon foils are used in the TOF section of JADE-I to produce start signals from secondary electron emission generated by interactions between the foil and incoming ions. However, these interactions can also alter the properties of the incident ions via carbon foil effects. Previous studies have shown that carbon foil effects vary depending on incident atomic species, energy, and angle. We developed a model that can characterize the carbon foil effects for Jovian magnetospheric ions measured by JADE-I. We will show ion composition analysis results on observations at high latitudes and in the plasmasheet by applying our model.
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27 - Variability of Jupiter’s IR H3+ aurorae during Juno approach
Luke Moore, James O’Donoghue, Henrik Melin, Tom Stallard, Chihiro Tao, Bertalan Zieger, John Clarke, Marissa F. Vogt, Tanapat Bhakyapaibul, Merav Opher, Gabor Tóth, John E. P. Connerney, Steve Levin, and Scott Bolton
We present ground-based observations of Jupiter’s H3+ aurorae over four nights in April 2016 while the Juno spacecraft was monitoring the upstream interplanetary magnetic field. High-precision maps of auroral H3+ densities, temperatures, and radiances reveal significant variabilities in those parameters, with regions of enhanced density and emission accompanied by reduced temperature. Juno magnetometer data, combined with solar wind propagation models, suggest that a shock may have impacted Jupiter in the days preceding the observation interval, but that the solar wind was quiescent thereafter. Auroral H3+ temperatures reveal a downward temporal trend, consistent with a slowly cooling upper atmosphere, such as might follow a period of shock recovery. However, the brightest H3+ emissions are from the end of the period, April 23rd. The lack of definitive signatures in the upstream interplanetary magnetic field lends supporting evidence to the claim that this brightening event may have been driven by internal magnetospheric processes.
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28 - Magnetosphere - Ionosphere - Thermosphere (MIT) coupling at Jupiter
Japheth Yates, Licia Ray, Nick Achilleos
Jupiter’s upper atmospheric temperature is considerably higher than that predicted by Solar Extreme Ultraviolet (EUV) heating alone. Simulations incorporating magnetosphere-ionosphere coupling effects into general circulation models have, to date, struggled to reproduce the observed atmospheric temperatures under simplifying assumptions such as azimuthal symmetry and a spin-aligned dipole magnetic field. Here we present the development of a full three-dimensional thermosphere model coupled in both hemispheres to an axisymmetric magnetosphere model. This new coupled model is based on the two-dimensional MIT model presented in Yates et al., 2014. This coupled model is a critical step towards to the development of a fully coupled 3D MIT model. We discuss and compare the resulting thermospheric flows, energy balance and MI coupling currents to those presented in previous 2D MIT models.
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29 - Comparison of a Physical Chemistry Model of the Io Plasma Torus with Measurements by JAXA’s Hisaki Mission, NASA’s Juno Mission and Other Earth-based Observations
Edward G. Nerney, Fran Bagenal, Andrew J. Steffl, & Kazuo Yoshioka
Io emits volcanic gases into space at a rate of about a ton per second. The gases become ionized and trapped in Jupiter’s strong magnetic field, forming a torus of plasma that emits 2 terawatts of UV emissions. Our recent work on re-analyzing UV data from Voyager, Galileo, & Cassini of the Io plasma torus has found that we can explain our observations of plasma conditions using a physical chemistry model with a neutral source of sulfur dioxide from Io (Nerney et al., 2017). We plan to continue our work by analyzing UV observations from JAXA’s Hisaki mission using our spectral emission model. We will constrain the torus composition with ground based observations. The physical chemistry model (adapted from Delamere et al., 2005) will then be used to match derived plasma conditions. We will correlate the oxygen to sulfur ratio of the neutral source with volcanic eruptions to understand the change in magnetospheric plasma conditions. Our goal is to better understand and constrain both the temporal and spatial variability of the flow of mass and energy from Io’s volcanic atmosphere to Jupiter’s dynamic magnetosphere. Through 2017-2018 the Io plasma torus will be monitored by JAXA’s Hisaki satellite and the magnetosphere mapped out by particles and fields instruments on NASA’s Juno spacecraft.
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30 - North and South: Simultaneous observations of both Jovian poles from Juno and the Hubble Space Telescope
Bertrand Bonfond, George R. Gladstone, Denis Grodent, , Zhonghua Yao, Jean-Claude Gérard, Thomas K. Greathouse, Maarten Versteeg, Vincent Hue, Michael W. Davis, Aikaterini Radioti, Scott J. Bolton, Steven M. Levin, John E. P. Connerney
On its elongated orbit, Juno flies over the poles of Jupiter every 53.5 days. The few hours before and after the perijove offer unique opportunities to observe the whole polar region from close distance. However, Juno’s instruments can only observe one hemisphere at a time. Fortunately, the Hubble Space Telescope points its 2.4 m mirror toward the opposite hemisphere during some of these time intervals, providing truly simultaneous observations of both poles. We compare observations from Juno-UVS with Far-UV imaging sequences from the Hubble’s Space Telescope Imaging Spectrograph (STIS). Juno-UVS acquires spectrally resolved images of ~17 ms exposure every 30 s Juno spin in the 70-205 nm wavelength range, while STIS can acquire about 270 consecutive 10 s images per HST orbit in the 130-160 nm range, but without any spectral resolution. Despite some differences, these datasets are similar enough in terms of spectral coverage, temporal and spatial resolution to allow direct comparisons. On Jupiter, the magnetic field is highly asymmetric and displays significant localized anomalies. Furthermore, most processes leading to auroral emissions depend on the magnetic field magnitude, either in the equatorial plane, in the acceleration regions, or in the upper atmosphere. Investigating morphological and brightness discrepancies between the two hemispheres provides precious clues on the current systems flowing in the magnetosphere and on the charged particles acceleration mechanisms.
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31 - Correcting Galileo’s Energetic Particle Detector (EPD) data; Methodology, Implications and Applications
Zoe Lee-Payne, Manuel Grande
Over the course of its 8 year mission the Energetic Particle Detector, launched in 1989 on the Galileo satellite, took data on the Jovian Particle environment. In the high radiation environment the EPD composition measurement system visibly decayed; higher mass particles, specifically oxygen and sulphur, read far lower energies and count rates at later epochs in the missions. By considering the non-steady accumulation of damage in the detector a correction method has been developed. Applying this correction method allows us to reanalyse the data. Specifically, we obtain new estimations on the surface weathering due to sputtering experienced by Europa and the other icy moons.
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32 - Variation of Jupiter's Auroral Electron Parameters Observed by Hisaki/EXCEED
Chihiro Tao, Tomoki Kimura, Fuminori Tsuchiya, Go Murakami, Kazuo Yoshioka, Hajime Kita, Atsushi Yamazaki, Sarah V. Badman, Nicolas André, Yasumasa Kasaba, Ichiro Yoshikawa, and Masaki Fujimoto
Long-term monitoring of Jupiter’s aurora is achieved by the Extreme Ultraviolet (EUV) spectrometer called EXCEED (Extreme Ultraviolet Spectroscope for Exospheric Dynamics) onboard JAXA’s Earth-orbiting planetary space telescope Hisaki until today after its launch in September 2013. The auroral electron energy is estimated using a hydrocarbon color ratio (CR) adopted for the wavelength range of EXCEED, and the emission power in the long wavelength range 138.5–144.8nm is used as an indicator of total emitted power before hydrocarbon absorption and auroral electron energy flux. We investigate the auroral parameters statistically to derive the typical values and their variations from a few hours to several months associated with the Io’s volcanic activity.
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33 - Variations of Bright Spot emission in Jupiter’s Polar Aurora
Kamolporn Haewsantati, Suwicha Wannawichian, John Clarke, Jonathan Nichols
Jupiter’s polar emission is a part of Jupiter’s aurora whose behavior is highly unstable with unclear explanation. A bright spot, one of ambiguous features in active region of Jupiter’s polar aurora was studied in this work. Jupiter’s aurora was observed by the Advanced Camera for Surveys (ACS), an instrument on board the Hubble Space Telescope (HST). The brightness and location variations of bright spots were analyzed. The variation of solar wind propagation at Jupiter obtained from the Michigan Solar Wind Model or MsWim was included in this study as well. Eight bright spots were clearly appeared among all Jupiter’s auroral images taken in May 2007. The reappearances of two bright spots in the same day were detected, suggesting occasional occurrence of bright spot. The ionosphere’s locations of eight bright spots were found to be varied within 10 degrees. Using Jupiter’s magnetosphere-ionosphere mapping based on VIP4, VIPAL, and GAM model, the bright spots’ origins in equatorial plane were predicted to be at distances over 70 Jovian radii with local times mostly in the daytime. The bright spots’ origins sometimes were mapped to distances beyond 150 Jovian radii or beyond dayside magnetopause. These results are suggested to be related to auroral phenomena in polar cusp and possibly associated with the solar wind. The role of solar wind propagation or other dynamics in bright spot’s behavior should be considered in deep detail.
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34 - Spatial Distribution and Properties of 0.1 – 100 keV Electrons in Jupiter’s Polar Region
R. W. Ebert, F. Allegrini, F. Bagenal, S. J. Bolton, J. E. P. Connerney, G. Clark, W. S. Kurth, S. Levin, P. Louarn, B. H. Mauk, D. J. McComas, C. Paranicas, M. Reno, J. R. Szalay, M. F. Thomsen, P. W. Valek, S. Weidner, and R. J. Wilson
In addition to the main emissions in the north and south, Jupiter’s ultraviolet (UV) auroral emissions also include satellite-related, polar and other features. Here, we focus on observations from Juno’s Jovian Auroral Distributions Experiment (JADE) of 0.1 – 100 keV electrons in Jupiter’s polar region, the region poleward of the main emission where the polar emissions are produced. Specifically, we examine the spatial distribution and properties of 0.1 – 100 keV electrons in Jupiter’s polar region during Juno's first and subsequent perijoves. Initial results from JADE show a complex environment consisting of mono- and bi-directional field aligned electron beams, regions void of electrons, and regions dominated by penetrating radiation. We present the pitch angle, energy spectra, and energy flux of these electrons and discuss their contribution to producing the polar UV emissions and to the electron environment in Jupiter’s polar region.
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35 - Wave particle interactions in Jupiter's magnetosphere and associated particle acceleration
J. Saur, A. Schreiner, B.H. Mauk, G.B. Clark, P. Kollmann
Jupiter’s magnetosphere is the most powerful planetary particle accelerator in the solar system. To help understand the associated processes, we investigate wave particle interactions, i.e., Landau and cyclotron damping, in Jupiter's magnetosphere for electrons, sulfur, oxygen and hydrogen ions. Therefore we calculate kinetic length and temporal scales, which we cross-compare at various regions within Jupiter's magnetosphere. Based on these scales, we investigate the roles of possible wave particle mechanisms in each region, e.g., Jupiter's plasma sheet, the auroral acceleration region and the polar ionosphere. We thereby consider that the magnetospheric regions are coupled through convective transport, and Alfven and other wave modes. We particularly focus on the role of kinetic Alfven waves in contributing to Jupiter’s aurora. Our results will aid the interpretation of particle distribution functions measured by the JEDI instrument onboard the JUNO spacecraft.
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36 - Magnetosphere-ionosphere coupling at Jupiter: Expectations for observations on Juno perijove passes based on a steady-state axisymmetric physical model
Stanley Cowley, Gabrielle Provan, Emma Bunce, and Jonathan Nichols
We evaluate the expected effects of magnetosphere-ionosphere coupling at Jupiter along Juno perijove passes using an axisymmetric physical model. As at Saturn, the model predicts distributed downward field-aligned currents over polar regions mapping to the tail and outer magnetosphere, closed principally through a ring of upward current mapping to the middle magnetosphere, which requires downward acceleration of magnetospheric electrons generating Jupiter’s main auroral emission. Auroral location, width, intensity, electron energy, and current density are in accord with values derived from previous ultraviolet imaging, such that the model forms an appropriate baseline for comparison with Juno data. In particular, evaluations of azimuthal field perturbations are derived for anticipated near-planet encounters with middle magnetosphere field lines on individual Juno perijove passes. We comment on model expectations in relation to initial results derived from Juno perijove data.
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37 - IPIM: A new numerical Jupiter ionosphere-auroras model
Baptiste Chide, Pierre-Louis Blelly, Mikel Indurain, Olivier Witasse, Aurélie Marchaudon
We study the Jovian ionosphere and the auroral energy deposition by developing a new numerical model based on a 16-moment fluid approach initially developed to describe the processes occurring at Earth (Marchaudon and Blelly, 2015). Our model computes the 1D transport of the plasma along interhemispheric magnetic field lines. For each ion (H+, H2+, H3+, He+, HeH+, and CH4+) and for the electrons, the density, the field aligned velocity, the parallel and perpendicular temperature and the field aligned components of the corresponding heat flows are provided. This model allows to derive the temperatures anisotropy in the high latitude regions. In addition, auroral emissions from the H3+ and H2 species are determined. As an input, the neutral atmosphere is taken from the data measured by the Galileo Probe descent (Seiff et al., 1998). The magnetic field is provided by the VIPAL model described in Hess et al., (2011). The precipitating electron fluxes are taken from Gustin et al. (2016). Simulations are run and compared with the available data, and predictions are made for the upcoming JUICE mission (Grasset et al., 2013).
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38 - Characteristics of solar wind control on Jovian UV auroral activity obtained from Hisaki EXCEED and ground-based observations
Hajime Kita, Tomoki Kimura, Chihiro Tao, Fuminori Tsuchiya, Hiroaki Misawa, Takeshi Sakanoi, Yasumasa Kasaba, Go Murakami, Kazuo Yoshioka, Atsushi Yamazaki, Ichiro Yoshikawa, Masaki Fujimoto
While the Jovian magnetosphere is known to be dominated by the internal source of plasma and energy, it also has an influence from the solar wind. We made a statistical analysis of the total power variation of Jovian UV aurora obtained by the spectrometer EXCEED (Extreme Ultraviolet Spectroscope for Exospheric Dynamics) on board the Hisaki satellite. We compared the total UV auroral power in 900-1480 A from 2014 to 2015 with solar wind model. The auroral total power shows a positive correlation to the duration of a quiescent interval of the solar wind before the enhancements of the dynamic pressure. One possible scenario to explain the results is that the magnetospheric plasma content controls the aurora response to the solar wind variation. A long quiescent interval would mean that plasma supplied from Io is more accumulated in the magnetosphere. The solar wind compression of the magnetosphere shifts the plasma inward and cause adiabatic heating to become hot and dense plasma, which leads to an enhancement of the field-aligned current. We also made a coordinated observation with Hisaki and CSHELL on Infrared Telescope Facility when Juno measured upstream solar wind. The intensity of infrared H3+ emission can be used as an index of the atmospheric heating, and the ion wind velocity distribution is related to field-aligned current. In this presentation, we will discuss a possible scenario for the solar wind control of the Jovian aurora including ground-based observations.
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39 - The Jovian Energetic Electron Spectrometer (JoEE) on the Particle Environment Package (PEP) for the ESA JUICE mission
George C. Ho, C. Paranicas, C.W. Parker, P.C. Brandt, S. Barabash and the Pep Team
The Jovian Energetic Electron (JoEE) sensor is a highly capable compact electron instrument on the Particle Environment Package (PEP) suite for the ESA’s JUICE spacecraft. JoEE employs the same electron measurement technique that was used on Cassini/MIMI and Galileo/EPD and provides electron measurements over the energy range from 25 keV to greater than 1.0 MeV. PEP science objectives are to measure charged and neutral particles in the Jupiter magnetospheres and at the moons to understand the magnetospheric and magnetosphere-moon interactions. JoEE, specifically, will take energetic electron measurement and be able to understand source(s) of the energetic electron in the Jovian radiation belt and its energization processes. By measuring large field-of-view (>180) and fine angular resolution (<25), JoEE is able to measure the instantaneous electron pitch-angle distributions and able to discriminate between open and closed Ganymede field lines. Here we describe the measurement requirements and novel measurement techniques that will make significant contribution in the JUICE mission.
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40 - Methods for estimation of radiation effects on particle instrument in Jupiter’s magnetosphere
Stefan Karlsson, Elias Roussos, Leif Kalla, Martin Wieser, Manabu Shimoyama, Goh Rusty Weixiong
Methods for estimation of radiation effects on particle instrument in Jupiter’s magnetosphere.
Charged energetic particle radiation is one important environment parameters that need to be considered for every space mission. This type of radiation is always present within our solar system and will be trapped around planets that hosing a magnetosphere. The planet with the strongest magnetic field is Jupiter, this leads to the most intense radiation belt in the solar system. In this environment, the penetrating electrons pose the main problems for spacecraft and payload. The radiation effects includes upset to electronics, accumulated dose degradation, displacement damage to components, background induced noise and deep dielectric charging.
PEP - Particle Environment Package for the JUICE (JUpiter ICy moons Explorer) mission is a plasma package with sensors to characterize the plasma environment in the Jovian system. PEP will measure density and fluxes of positive and negative ions, electrons, exospheric neutral gas, thermal plasma and energetic neutral atoms. This work describes the methods for estimate radiation effects for the PEP payload. Methods includes the use of different 3D radiation tools like sectoring shielding analysis and Monte Carlo simulations (GRAS Geant4). The result from different methods is compared with each other and with existing data from Galileo EPD that was orbiting Jupiter atmosphere in the beginning of the 1990s.
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41 - Particle Environment Package (PEP) for the ESA JUICE mission
Stas Barabash, Pontus Brandt, Peter Wurz, and the Pep team
The PEP suite explores the particle populations in the Jovian system to answer three overarching science questions (1) How does the corotating magnetosphere of Jupiter interact with Ganymede, Callisto, Europa, and Io? (2) How do internal and solar wind drivers cause such energetic, time variable and multi-scale phenomena in the steadily rotating giant magnetosphere of Jupiter? (3) What are the structure and composition of the icy moons exospheres and how do they response to the external conditions?
PEP measures positive and negative ions, electrons, exospheric neutral gas, thermal plasma and energetic neutral atoms (ENA) present in all domains of the Jupiter system over nine decades of energy from < 0.001 eV to > 1 MeV with full angular coverage. PEP includes 6 (six) sensors (1) an ion mass analyzer, (2) an electron spectrometer, (3) a low energy ENA imager, (4) a high energy ENA and energetic ions imager, (5) an energetic electron sensor, and (6) a neutral gas and ions mass spectrometer. For the first time at Jupiter PEP combines global imaging via remote sensing using ENAs with in-situ measurements and performs global imaging of Europa/Io tori and magnetosphere combined with energetic ion measurements. Using low energy ENAs originating from the particle – surface interaction PEP investigate space weathering of the icy moons by precipitation particles. PEP will first-ever directly sample the exospheres of Europa, Ganymede, and Callisto with high mass resolution.
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42 - The search for Europa plume signatures in Galileo plasma particle data
Hans Huybrighs, Elias Roussos, Norbert Krupp, Markus Fraenz, Yoshifumi Futaana, Stas Barabash, Karl-Heinz Glassmeier
Recent observations by the Hubble space telescope hint at recurring water vapour plumes originating from Europa’s surface. In-situ sampling of these plumes could allow for the study of Europa’s potentially habitable ocean without the need of having to land on it’s icy surface.
Lacking in the body of evidence for these plume are indisputable in-situ observations of the plumes. No opportunity to study these plumes in-situ will arise before the early 2030’s when ESA’s JUICE mission or NASA’s Europa Clipper will arrive. However, it may be possible that the Galileo mission, active in the Jupiter system from 1995 to 2003, could have encountered these plumes. In particular it has been suggested that the high plasma densities and anomalous magnetic fields measured during the E12 flyby could be connected to plumes.
In this work we present an overview of in-situ data obtained by the Galileo spacecraft during the Europa flybys it made and compare the data in the context of the search for signs of active plumes. Focus is in particular on the data obtained with the plasma instruments PLS (low energy ions and electrons) and EPD (high energy ions and electrons).
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43 - Interaction of the magnetospheric plasma with the Jovian moons for the formation of their atmospheres and ionospheres: NIM / PEP investigations
Audrey Vorburger, Peter Wurz, André Galli, Martin Rubin, Pontus Brandt, Stas Barabash
The Galilean moons are all located well within the Jovian magnetosphere, thus constantly interact with the Jovian plasma. These interactions are mainly governed by conductive sub-surface layers (internally generated magnetic fields), the atmospheric / ionospheric compositions, densities, and mass loading, and the properties of the plasma upstream of the satellites’ locations. This interaction not only modifies the local Jovian plasma properties, but also controls the satellites' atmospheres / ionospheres, most noticeably through sputtering (adding material), ionization & pick-up (removing material), and radiolysis.
The JUICE / ESA mission to the Jovian system is designed to investigate in detail Jupiter and its Galilean moons. The Neutral Ion Mass Spectrometer (NIM), one of the instruments of the Particle Environment Package (PEP), will conduct direct sampling of the exospheric neutral gas and thermal plasma at Europa, Ganymede, and Callisto, investigating the interaction between the Jovian plasma and these satellites. Special interest is given to Europa’s gas release to space and sub-surface release (plumes).
In preparation of the JUICE science phase we simulated the interaction by a Monte Carlo model, coupled to a MHD model, which predicts the densities and relative abundances in the exospheres and ionospheres. We show the expected NIM measurements at the three satellites, including local or temporary changes of the atmosphere, e.g., originating from the presence of plumes.
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44 - Electron measurements in the low-latitude magnetosphere of Jupiter and in the vicinity of the Galilean moons: Current knowledge and future investigations with the PEP JEI and JoEE sensors onboard the JUICE spacecraft
Norbert Krupp, Markus Fränz, Elias Roussos, Hans Huybrighs, Stas Barabash, Pontus C. Brandt, Chris Paranicas, Donald G. Mitchell, Joseph Westlake, Krishan Khurana, Xianzhe Jia
The Jovian magnetosphere is one of the most fascinating plasma laboratories in space. Driven and powered by the fast rotation of the planet and filled with neutral and charged particles from the internal particle sources, plasma processes evolve on a variety of spatial and temporal scales in the system. In this presentation we will first summarize the results of electron measurements in the Jovian system from previous missions, such as periodicities of electron intensities, transition from bi-directional to trapped electron distributions, relation between electron beams and aurora, injections and interchange transport, radial distribution of energetic electrons. Another target of the electron sensors is to detect photo-electrons possibly generated in the exospheres of the Galilean moons.
JUICE/PEP Electron sensors, JEI and JoEE, will go beyond previous missions to provide the long-sought for 3D electron plasma distributions and to reveal the missing link in electron acceleration mechanisms that makes Jupiter the biggest particle accelerator in the solar system.
After presenting PEP/JEI and its science goals, we will also discuss how the combined observations with the energetic electron detector PEP/JoEE in the equatorial and mid-latitude magnetosphere as well as during the moon flybys at Europa, Ganymede, and Callisto, will enhance the science output and provide important context for further understanding of past observations with Galileo/EPD.
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45 - The Jovian Energetic Neutrals and Ions (JENI) 2nd Generation ENA and Ion Camera of the Particle Environment Package (PEP) on board the JUICE Mission
Pontus C. Brandt, Donald G. Mitchell, Joseph H. Westlake
Following the success of Cassini/INCA and IMAGE/HENA, JENI is the second-generation NASA-funded ENA and Ion camera now being developed for flight on the JUICE Mission. JENI images the Europa gas cloud and magnetospheric injections, and in its ion-mode, captures the energetic particle pressure of H+, O+, and S+.
JENI uses ultrathin foils and TOF with a triple coincidence system for efficient background rejection to achieve measurements of ions in the 0.5 keV - 5 MeV range and ENA imaging in the 0.5 – 300 keV range with 2 degrees resolution. Two foil-covered slits provide a start pulse and position as the primary particle (ion or ENA) enters the sensor. A foil-covered, imaging MCP provides the 2D stop position and timing pulse. Electrons back-scattered from the stop foil are used as a very narrow coincidence timing window with a spatial coincidence. A deflection plate system in front of the aperture slits rejects charged particles up to about 300 keV in its ENA imaging mode.
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46 - The Search-Coil Magnetometer onboard ESA JUICE mission
A. Retinò, M. Mansour, T. Chust, P. Canu, F. Sahraoui, O. Le Contel, D. Alison, G. Sou, L. Varizat, J.-D. Techer, A. Jeandet, N. Geyskens, M. Chariet, B. Cecconi, J.-E. Wahlund
The JUpiter ICy moons Explorer (JUICE) mission is the first large-class (L1) mission in ESA Cosmic Vision. JUICE is planned for launch in 2022 with arrival at Jupiter in 2029 and will spend at least three years making detailed observations of Jupiter’s magnetosphere and of three of its largest moons (Ganymede, Callisto and Europa). The Radio and Plasma Wave Investigation (RPWI) consortium will carry the most advanced set of electric and magnetic fields sensors ever flown in Jupiter’s magnetosphere, which will allow to characterize the radio emission and plasma wave environment of Jupiter and its icy moons. Here we present the scientific objectives and the technical features of the Search Coil Magnetometer (SCM) of RPWI. SCM will provide for the first time high-quality three-dimensional measurements of magnetic field fluctuations’ vector in the frequency range 0.1 Hz – 20 kHz within Jupiter’s magnetosphere. High sensitivity (4 fT × Hz-1/2 at 4 kHz) will be assured by combining an optimized (20 cm long) magnetic transducer with a low-noise (4 nV × Hz-1/2 ) ASICs pre-amplifiers for the front-end electronics. Perturbations by the spacecraft will be strongly reduced by accommodating SCM more than 8m away from the spacecraft on JUICE magnetometer boom. The combination of high sensitivity and high cleanliness of SCM measurements will allow unpreceded studies of waves and turbulence down to electron scales, in particular in key regions such as the magnetopause, the auroral region and the magnetotail current sheet of Ganymede’s magnetosphere. This will lead to important advances in understanding plasma transport and particle energization mechanisms in Jupiter’s magnetosphere.
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47 - Imaging of energetic neutral atoms with the Jovian Neutral Atoms Analyser onboard JUICE: Expectations from charge exchange processes in Ganymede orbit
Maike Brigitte Neuland, Kazushi Asamura, Stas Barabash, Yoshifumi Futaana, Manabu Shimoyama, Martin Wieser
The JUICE mission will be launched in 2022 and reach Jupiter and the Jovian system 8 years later. The Jovian Neutral Atoms Analyser (JNA) is one of the sensors of the Particle Environment Package (PEP) onboard JUICE. JNA will measure energetic neutral atoms in an energy range from 10eV to 3keV with an angular resolution 11°x7° resolving hydrogen and heavy atoms. One of the main JNA science objectives is to investigate the plasma dynamics in the Ganymede magnetosphere using ENA imaging. Low energy ENAs produced via sputtering and backscattering will be used to image the precipitation regions and, in particular, a boundary of open and closed field lines. ENA produced via charge – exchange between the plasma on the Ganymede magnetosphere and exosphere can be used to obtain the global plasma distribution. For a better understanding of the expected fluxes and the fraction of neutrals from charge exchange processes, we modelled the latter using an existing dataset from [Fatemi et al, Geophys. Res. Lett. 43(10), 2016], the according charge exchange cross sections from [Scherer et al., A & A 563, 2014] and the model of the Ganymede exosphere from [P. Wurz et al., Exo - Climes III , 2014]. We will present the results from our model and the impact of these on JNA testing and calibration.
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48 - The Jovian Plasma Dynamics and Composition Analyzer on JUICE
Martin Wieser, Stas Barabash
The Jovian plasma Dynamics and Composition analyzer (JDC) is one of six sensors within the Particle Environment Package (PEP) on ESA's JUICE mission to Jupiter.
JDC measures 3D distribution functions of positive and negative ions inclusive electrons in the energy range 1 eV per charge to 41 keV per charge.
Full hemispherical angular coverage is achieved with 16 radial sectors and scanning electrostatic deflectors. A time-of-flight section is used to determine ion masses
simultaneously with high sensitivity but low mass resolution and lower sensitivity but high mass resolution. JDC features of a compact electrostatic analyzer with spherical sectors,
start signal generation by surface interaction and a reflectron-type time-of-flight section. The Jovian radiation environment is the main driver for the instrument design. Detailed radiation modelling, shielding design and coincidence schemes for particle detection allow JDC to operate in this challenging environment.
We review science objectives of JDC, present the sensor principle and design, its predicted performance in the Jovian environment and compare to most recent laboratory measurements from JDC sensor prototypes.
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49 - Feasibility of the exploration of the subsurface structures and ionosphere of Jupiter's icy moons by interferences of Jovian radio waves
A. Kumamoto, Y. Kasaba, F. Tsuchiya, H. Misawa, H. Kita, W. Puccio, J. E. Wahlund, J. Bergman, B. Cecconi, Y. Goto, J. Kimura, and T. Kobayashi
A new passive radar technique using interference patterns in the spectrum of the Jovian radio waves has been proposed, and investigated for implementation to JUICE (Jupiter Icy Moons Explorer)/ RPWI (Radio and Plasma Wave Instrument). When there occurs interference among Jovian radio waves directly from Jupiter (W1), those reflected at the ice crust surface (W2), and those reflected at the subsurface reflectors in the ice crust (W3), fine and wide interference patters can be found in the spectrum. Fine patterns are caused by interference between W1 and W2, and between W1 and W3. Wide patterns are caused by interference between W2 and W3. In order to observe these interference patterns, the receiver is required to resolve 100 Hz, and downlink spectra with a frequency range of 2 MHz and resolution of 1 kHz. Based on the calculation of the attenuation rate of the radio waves in the ice from 80 K (surface) to 250 K (at the ice crust bottom), the intensity of the subsurface echo was estimated. Due to extremely high attenuation around the melting temperature, subsurface echoes from depth up to 140 km (just above the ice crust bottom) are expected to be detected. In addition to the subsurface structures, group delay due to ionospheric plasma can be determined by fine interference patterns. When total electron content (TEC) below the spacecraft at an altitude of 500 km is 10^15 /m^2, the frequency intervals of the fine interference becomes 8 % narrower than those expected in vacuum.
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50 - JUICE-UVS and Europa-UVS Science Synergies and Juno-UVS Pathfinding
Kurt D. Retherford, G. Randall Gladstone, Thomas K. Greathouse, Michael W. Davis
Present and upcoming exploration of the Jupiter system includes Ultraviolet Spectrograph (UVS) investigations all sharing the same basic instrument design. ESA’s Jupiter Icy Moons Explorer (JUICE) mission and NASA’s Europa Clipper mission are currently both planned to launch in 2022, and their JUICE-UVS and Europa-UVS instruments are in Phase C & Phase B, respectively. These instruments under development are closely related in design to the Juno-UVS instrument, in terms of the modern microchannel plate (MCP) detector technology incorporated and the inclusion of robust shielding from the intense MeV electron radiation environment. These three instruments make up the fourth, fifth, and sixth instruments in a series of successful ultraviolet imaging spectrographs starting with Rosetta-Alice, New Horizons Pluto-Alice, and the Lunar Reconnaissance Orbiter (LRO) Lyman Alpha Mapping Project (LAMP). JUICE-UVS and Europa-UVS observe photons in the 55-210 nm wavelength range, slightly expanded relative to Juno-UVS’s 70-200 nm. For JUICE-UVS and Europa-UVS, three distinct apertures send light to the off-axis telescope mirror feeding the long-slit spectrograph, while Juno-UVS has a front-end scan mirror to tailor its views of Jupiter’s auroral ovals while the spacecraft spins. We further present a comparison of the three UVS investigations by describing the science we plan to address – and synergies, the salient details of the instruments, and the basic concept of operations for each.
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51 - Science objectives and implementation of Software-type Wave-Particle Interaction Analyzer (SWPIA) by RPWI for JUICE
Y. Katoh, H. Kojima, K. Asamura, Y. Kasaba, F. Tsuchiya, Y. Kasahara, T. Imachi, H. Misawa, A. Kumamoto, S. Yagitani, K. Ishisaka, T. Kimura, M. Hikishima, Y. Miyoshi, M. Shoji, M. Kitahara, O. Santolik, J. Bergman, W. Puccio, R. Gill, M. Wieser, W. Schmidt, S. Barabash, and J.-E. Wahlund
Software-type Wave-Particle Interaction Analyzer (SWPIA) will be realized as a software function of Low-Frequency receiver (LF) running on the DPU of RPWI (Radio and Plasma Waves Investigation; PI: J.-E. Wahlund, IRF-Uppsala, Sweden) for the ESA JUICE mission. SWPIA conducts onboard computations of physical quantities indicating the energy exchange between plasma waves and energetic ions. Onboard inter-instruments communications are necessary to realize SWPIA, which will be implemented by efforts of RPWI, PEP (Particle Environment Package; PI: Stas Barabash, IRF-Kiruna, Sweden) and J-MAG (JUICE Magnetometer; PI: M. Dougherty, ICL, UK). By providing the direct evidence of ion energization processes by plasma waves around Jovian satellites, SWPIA contributes scientific output of JUICE as much as possible with keeping its impact on the telemetry data size to a minimum; SWPIA outputs 0.2 kB at the smallest from 440 kB waveform and particle raw data.
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52 - The Jovian Energetic Neutral Analyzer for the Particle Environment Package onboard JUICE
Manabu Shimoyama, Martin Wieser, Stas Barabash, Kazushi Asamura, Stefan Karlsson, Maike Brigitte Neuland, Yoshifumi Futaana
Jovian Neutral Analyzer (JNA) is one of six sensors in the Particle Environment Package onboard ESA’s JUICE mission to Jovian system. The JNA provides the low-energy (10 eV – 3.3 keV) ENA images originating from the Jovian magnetospheric plasma interaction with the surface/magnetosphere of the Galilean icy moons, and Io torus images through ENA emissions generated from charge-exchange between the co-rotating plasma and the neutral torus. Although the design of the JNA is based on the heritage of CENA instrument onboard Chandrayaan-1 mission to the Moon and the ENA instrument onboard Bepi-Colombo mission to Mercury, a major design update is required to adapt to a very harsh radiation environment in Jupiter. The operation of the JNA combines the techniques of charge conversion surface, electrostatic energy analysis and time-of-flight (TOF) analysis using a start surface and channel electron multipliers (CEMs). Combination of energy and TOF analysis enables mass/charge separation between hydrogen and heavier species such as oxygen and sulfur atoms. Incident direction of ENA is determined by 11 sets of start and stop CEMs which are azimuthally placed around the instrument axis. To suppress background noise due to high energy electrons and gamma rays, the TOF pass length is substantially shrunk compared to the predecessors. We will present the principle and predicted performance of the JNA together with results from prototype tests.
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53 - HST observations of variations in Ganymede’s oxygen atmosphere and aurora
P. M. Molyneux, J. D. Nichols, N. P. Bannister, E. J. Bunce, J. T. Clarke, S. W. H. Cowley, J.-C. Gérard, D. Grodent, S. E. Milan and C. Paty
We analyze the OI] 135.6 nm/OI 130.4 nm intensity ratio at Ganymede from HST/STIS and HST/COS auroral observations and find a range of values that are best explained by a significant difference in the atmospheric compositions of the satellite’s leading and trailing hemispheres. The ratio observed on the leading hemisphere is consistently larger than that on the trailing hemisphere. The range of ratios observed implies a trailing hemisphere atomic oxygen column density up to ten times larger than that on the leading hemisphere. We also observe a difference in the response of the aurora of the two hemispheres when Ganymede moves close to the center of the plasma sheet, with an increase in the emission intensity seen on the leading hemisphere and a reduction in the brightness of the trailing hemisphere aurora. This has previously been attributed to an observed shift in the location of the aurora to higher latitudes on the trailing hemisphere and lower latitudes on the leading hemisphere, but a larger Alfvén Mach number due to increased plasma density and a weaker magnetic field at the center of the plasma sheet may also contribute to the effect by reducing the access of electrons to the trailing hemisphere.
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54 - Jovian Plasma Interactions with Europa's Exosphere
John Hale, Carol Paty, Alexia Payan, Frank Crary, Ayanna Jones
In anticipation of the arrival of the Europa Clipper mission at its destination, this preliminary work characterizes the interaction of Europa with the Jovian magnetosphere using a multifluid MHD treatment. In order to adequately accomplish this, the system is simulated in multiple relevant configurations, including cases in which Europa is without an exosphere and cases with an exosphere. While not a reflection of reality, simulations of the system without a Europan exosphere—and ionosphere—allow for quantification of the effects of the induced dipole separate from those of plasma sourced at Europa. In the cases in which an exosphere is simulated, asymmetries due to the sputtering derived nature of the exosphere are included. Ionization of exospheric material is calculated dynamically using electron impact ionization, photoionization, and ion charge exchange. Additionally, changes between when Europa is inside of or outside of the Jovian plasma sheet are investigated, as this may cause significant alteration to the Europan ionosphere between Europa Clipper’s various flybys.
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55 - Multi-fluid MHD modeling of Europa’s variable interaction with Jupiter’s magnetosphere
Camilla Harris, Xianzhe Jia, James Slavin, Martin Rubin, Gábor Tóth
The Galileo flybys of Europa and subsequent simulations have established that plasma interactions at Europa depend heavily on Europa’s location within Jupiter’s rotating magnetosphere, specifically proximity to the plasma sheet and time variation in the ambient magnetic field. Here we simulate the sub-Alfvénic interaction between Europa’s ionosphere, exosphere, and induced dipole and Jupiter’s magnetosphere with 3D multi-fluid, steady-state, Hall MHD simulations based on BATSRUS. Our plasma interaction model incorporates three ion fluids, an electron fluid, and mass-loading processes to address outstanding questions concerning the interaction between Europa’s exosphere and Jupiter’s plasma sheet. The ion fluids are O+ and singly ionized molecular Oxygen (O2+) originating in Europa’s exosphere, and O+ originating in Jupiter’s magnetosphere. The mass-loading processes include photoionization, charge-exchange, recombination, and collisions. They describe the interaction between magnetospheric plasma and Europa’s neutral exosphere, and distinguish magnetospheric from exospheric O+. We apply our model to different Galileo flybys and compare model results with magnetic field and plasma observations. We then determine the rate of mass loss from Europa’s ionosphere and exosphere to Jupiter’s plasma sheet, the magnitude and geographic distribution of Jovian plasma incursion to Europa’s surface, and how these features vary with Europa’s location in Jupiter’s magnetosphere.
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56 - Interaction of Europa with Jovian Plasma Torus: Multi-species Hybrid Simulations
Ondřej Šebek, Pavel Trávníček, Petr Hellinger
We present results of a simulation study of the interaction of Europa with
Jupiter’s magnetospheric plasma compared to in situ observations of Galileo
spacecraft. For simulations we use multi-species three dimensional global
hybrid (kinetic ions and fluid electrons) model. The plasma at Europa is composed of pick-up ions which represent an obstacle for the streaming Jovian magnetic field and plasma resulting in the compression of the magnetic field lines which in return causes development of temperature anisotropies.
We consider O+ , S++, O++, and S++, as the main constituents of the Jovian
plasma torus at Europa while its neutral atmosphere is considered to be
composed primarily of (neutral) O2 molecules. We consider ionization
processes of the neutral O2 atmosphere which is then a source of dense
population of pick-up ions at Europa. We examine global structure of the
interaction, formation of Alfvén wings, development of temperature anisotropies
and corresponding instabilities, and the fine phenomena caused by the
multi-species nature of the plasma. We compare the simulated results with in
situ measurements of the Galileo spacecraft.
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57 - Plasma interaction at Io: Multi-species hybrid simulations
Ondřej Šebek, Pavel Trávníček, Raymond Walker, Petr Hellinger
We present analysis of global 3-dimensional multi-species hybrid
simulations of Io's interaction with Jovian magnetospheric plasma. In
the multi-species simulations we assume five species, plasma torus is
composed of O+, S+ and S++ ions and ions of SO+, SO2+ are created
around Io by ionization of its neutral atmosphere. We consider several
ionization processes, namely, charge exchange ionization and
photoionization/electron impact ionization. We compare our results to
data acquired by the Galileo spacecraft. Our results are in a good
qualitative agreement with the in situ magnetic field measurements
made during Galileo’s flybys around Io.
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58 - Neutral loss at Europa and Io
Vincent Dols, Fran Bagenal, Frank Crary
Extended neutral clouds are detected along the orbit of Io and Europa. Na, K, S, and O were detected at Io, thanks to spectroscopic observations (Brown, 1974,1981; Trafton 1981; Durrance et al., 1983,1995; Thomas 1996; etc.). The observations at Europa are more indirect: ENA (Mauk et al., 2003), EPD fluxes (Lagg et al., 2003), Lyman-Alpha (Roth et al., 2016). These clouds constitute the main source of plasma for the jovian magnetosphere. As neutral are notoriously difficult to observe (except Na), the composition and the density of these clouds are still uncertain. The processes that lead to neutral escape are diverse: atmospheric and surface sputtering, molecular dissociation, molecular ion recombination, Jeans escape etc. Each process is locally variable and leads to atomic or molecular neutrals escaping at different velocities (i.e. electron impact dissociation leads to very slow atomic neutrals, sputtering might eject faster molecular neutrals).
A future modelisation of the formation of these neutral clouds requires the estimation of the escape rate of each process as well as its localization (upstream, downstream, jovian/anti-jovian etc.). We propose to quantify and localize the escape processes from the atmosphere with a coupled MHD/ multi-species chemistry model, using a prescribed atmospheric distribution consistent with the observations.
We will compare the neutral loss rate at Io and Europa .
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59 - Modeling the response of the Io plasma torus to hot electron modulation and volcanic eruptions
Drew Coffin, Peter Delamere
The response of the Io plasma torus to superthermal electron modulation and volcanic eruptions is studied using a two-dimensional physical chemistry model (Copper et al., 2016). The model includes radial and azimuthal transport, latitudinally-averaged physical chemistry, and prescribed System III superthermal electron modulation following Steffl et al., [2008]. Volcanic eruptions are modelled as a temporal Gaussian enhancement (e.g., 2x) of the neutral source rate and hot electron fraction (e.g., <1%). However, we adopt an alternative approach for the Steffl et al., [2008] System IV electron modulation. Coupling hot electrons to radial transport, the modulation is determined by the radial flux tube content gradient. Radially-dependent subcorotation is prescribed, consistent with observations [Brown, 1994; Thomas et al., 2001]. We find that the model produces a radially-independent periodicity that is consistent with System IV, which may be directly coupled to subcorotation. We also find that post-eruption, the ionic composition of the torus changes and UV emission rate decreases but in a distinctly different manner for the inner (< 8.5 Rj) and outer (> 8.5 Rj) torus. The pre-eruption-normalized power radiated (ΔPUV) in the inner torus retreats inward while in the outer torus the enhancement transports outward through the boundary. We infer that the recovery is chemically-dominated in the inner torus, and transport-dominated in the outer torus.
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60 - Cassini UVIS Observations of Io’s Extended Neutral Cloud
Andrew J. Steffl
Material escaping Io’s atmosphere forms an extended cloud, ahead of and behind Io in its orbit around Jupiter. This cloud, primarily composed of neutral oxygen and sulfur atoms, is the source of the majority of plasma in the Io torus. The extended neutral cloud is both faint and difficult to observe, which is why, more than 40 years after the discovery of the Io torus, its spatial extent remains poorly known. Inspired by the exciting new results from JAXA’s Hisaki mission (please see presentations by R. Koga and others), I have re-analyzed Cassini UVIS FUV observations made during the Jupiter flyby in late 2000/early 2001. Both neutral oxygen and neutral sulfur have prominent emission lines in the wavelength region covered by the UVIS FUV channel, oxygen at 1304Å and 1356Å and sulfur at 1388Å and 1474Å, all of which are clearly detected. The brightness of the neutral emissions is sharply peaked near Io. Together with observations from Hisaki, these data reveal the spatial extent of Io’s extended neutral clouds for the first time.
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61 - Response of Jupiter’s inner magnetosphere to the solar wind derived from 3-years observation by Hisaki
Go Murakami, Kazuo Yoshioka, Tomoki Kimura, Atsushi Yamazaki, Fuminori Tsuchiya, Chihiro Tao, Hajime Kita, Masato Kagitani, Yasumasa Kasaba, Ichiro Yoshikawa, and Masaki Fujimoto
Because Jupiter’s magnetosphere is huge and is rotationally dominated, solar wind influence on its inner part has been thought to be negligible. Meanwhile, dawn-dusk asymmetric features of this region have been reported. Presence of dawn-to-dusk electric field is one of the leading explanations of the asymmetry; however, the physical process of generating such an intense electric field still remains unclear. Using long and continuous monitoring of the extreme ultraviolet emissions from the Io plasma torus (IPT) in Jupiter’s inner magnetosphere made by the Hisaki satellite between December 2013 and March 2014, it was revealed that the dusk/dawn brightness ratio of the IPT clearly responses to rapid increase of the solar wind dynamic pressure. The observation indicates that dawn-to-dusk electric field in the inner magnetosphere is enhanced under compressed conditions. Here we present the result of statistical analysis of this feature by using all Hisaki data with IPT monitoring between December 2013 and August 2016. We found clear correlation between the dusk/dawn brightness ratio and solar wind dynamic pressure.
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62 - Io in Silhouette: Mapping Io’s SO2 atmosphere during Jupiter transit events
Tracy M. Becker, K. D. Retherford, L. Roth, L. Feaga, C. C. Tsang, K. L. Jessup, C. Grava
The interplay between Io’s atmosphere and Jupiter’s magnetosphere is a key driver of the plasma environment of the Jovian system. We present a unique analysis of the spatial distribution of Io’s SO2 atmosphere using far-UV observations from the Hubble Space Telescope Imaging Spectrograph (STIS). On four occasions, we observed Io as it transited Jupiter, exploiting the planet’s bright Lyman-alpha dayglow to measure the absorption of that signal off of Io’s limb. Because the photoabsorption cross-section for sulfur dioxide peaks near 122 nm, measurements of the optical depth due to absorption at these wavelengths quantifies the column density of SO2 vapor above the surface. Our results confirm previous observations that the density of SO2 near Io’s equator is roughly an order of magnitude higher than that near the poles. In addition to incorporating the STIS point spread function in our models of the Io transit data, we also consider additional attenuation due to atmospheric hydrogen, which is produced by charge exchange reactions between magnetospheric protons and Io's atmosphere. We will present details of our Io transit models, the results, and their implications for the driving source (volcanic vs. sublimation) of SO2 in Io’s atmosphere.
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63 - Europa’s Hydrogen Corona in a Large Set of HST Lyman-Alpha Images
Sofia Bergman, Lorenz Roth, Nickolay Ivchenko
UV spectral images of Europa were obtained by the Space Telescope Imaging Spectrograph (STIS) on the Hubble Space Telescope (HST) on 20 occasions between the years 1999 and 2015. In this study these data are analysed to look for Lyman-alpha emissions from a hydrogen corona. This hydrogen corona was recently discovered in absorption by Roth et al. (2017), also from HST Lyman-alpha images but with Europa in transit of Jupiter. The aim of this study is to confirm the existence of the corona also in emission. We develop a model for the expected emissions from an escaping hydrogen atmosphere and compare it to the data. We furthermore look for systematic variability over time, large scale asymmetries and connections to the local plasma and magnetospheric environment.
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64 - On the orbital variability of Ganymede’s and Europa’s atmospheres
Francois Leblanc, Apurva Oza, Robert E. Johnson, Ludivine Leclercq, Carl Schmidt, Ronan Modolo, Jean-Yves Chaufray, Tim Cassidy
The atmospheres of Ganymede and Europa atmospheres are produced by radiative interactions with their icy surfaces, sourced by the Sun and Jovian plasma. Sputtered and thermally desorbed molecules are tracked in our Exospheric Global Model (EGM), a 3-D parallelized collisional model. This code was developed to reconstruct the formation of the upper atmosphere/exosphere of planetary bodies interacting with the solar photon flux and the magnetospheric plasma. Here, we describe the spatial distribution of the H2O and O2 atmospheres, and their variability with the satellite rotation around Jupiter. In particular, we show that the O2 atmosphere is characterized by timescales of the order of the rotational period. Jupiter's gravity is a significant driver of the spatial distribution of the heaviest exospheric components. Both sourcing and Jovian gravity are needed to explain the observed auroral emissions at Ganymede, as well as the persistent dawn/dusk asymmetry in the Europa exosphere.
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65 - Ganymede’s atomic hydrogen atmosphere and surface reflectivity in HST/STIS Lyman-α images
Juan Alday, Lorenz Roth, Nickolay Ivchenko, Tracy M. Becker, Kurt D. Retherford, Joachim Saur
An extensive number of far-ultraviolet observations of Ganymede’s auroral and atmospheric emissions were obtained by the Space Telescope Imaging Spectrograph (STIS) of the Hubble Space Telescope (HST) from 1998-2014. The images were obtained when Ganymede was located at different orbital phase, providing information about both the trailing and leading hemispheres. We analyze the hydrogen Lyman-α (1216 Å) signal and model the different contributing sources. The comparison between the images and the model provides information about the temporal and hemispherical variability of atomic hydrogen in Ganymede’s atmosphere. Additionally, the images allow us to study the reflectivity of the moon’s surface at Lyman-α, which appears to be anti-correlated with images at visible wavelengths.
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66 - 3D Hall MHD-EPIC Simulations of Ganymede’s magnetosphere
Hongyang Zhou, Gabor Toth, Xianzhe Jia
Fully kinetic model of a complete 3D magnetosphere is still computationally expensive and not feasible considering present capability of processors while magnetohydrodynamic (MHD) model has been successfully applied in a wide range of plasma simulation. We have recently developed a new modeling tool to embed the implicit particle-in-cell (PIC) model iPIC3D into the Block-Adaptive-Tree-Solarwind-Roe-Upwind-Scheme magnetohydrodynamic (MHD) model. This results in a global kinetic model of a complete magnetosphere, and the model is now able to use stretched spherical coordinates with adaptive mesh refinement (AMR) in key regions of the magnetosphere and adopts a semi-implicit scheme for solving the magnetic induction equation using large time steps. We have applied the model to Ganymede, the only moon in the solar system known to possess a strong intrinsic magnetic field, and included finite resistivity beneath the moon`s surface to model the electrical properties of the interior in a self-consistent manner. The kinetic effects of electrons and hot ions on the dayside magnetopause and tail current sheet are captured with iPIC3D. Our simulation provides better understanding of the global magnetospheric structure as well as the flux transfer events and magnetic reconnection under sub-Alfvènic plasma conditions
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67 - Callisto plasma interactions - now with an ionosphere
Jesper Lindkvist, Mats Holmström, Krishan K. Khurana, Maria Hamrin
We use a hybrid model to study the plasma interaction between the Jovian magnetosphere and the Galilean moon, Callisto. Situated far from Jupiter, Callisto is experiencing a highly variable external magnetic field, resulting in the highest relative inductive response of the Galilean moons. Callisto has an atmosphere of mainly carbon dioxide, which when ionised by photons or electron impacts will be picked up by the convective electric field of the Jovian magnetosphere. With the neutral atmosphere represented by macroparticles, we are not limited by the resolution of the simulation cell size, and can resolve the scale height of Callisto's atmosphere. We investigate the importance of asymmetric neutral sublimation while varying the direction of the Sun with respect to the magnetospheric plasma flow. This could answer what conditions have to be met for a global/local ionosphere to exist.
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68 - Plasma Interaction and Energetic Particle Dynamics near Callisto: A Case Study of the Galileo C10, C21, and C23 Flybys
Lucas Liuzzo, Sven Simon, Moritz Feyerabend, Uwe Motschmann
Callisto’s magnetic environment is characterized by a complex admixture of induction signals from its conducting subsurface ocean, the interaction of corotating Jovian magnetospheric plasma with the moon’s ionosphere and induced dipole, and the non-linear coupling between the effects. In contrast to other Galilean moons, ion gyroradii near Callisto are comparable to its size, requiring a kinetic treatment of the interaction region near the moon. Thus, we apply the hybrid simulation code AIKEF to constrain the competing effects of plasma interaction and induction. We determine their influence on the magnetic field signatures measured by Galileo during the C10, C21, and C23 Callisto flybys. We use the magnetic field calculated by the model to investigate energetic particle dynamics and their effect on Callisto’s environment. From this, we provide a map of global energetic particle precipitation onto Callisto’s surface, which may contribute to the generation of its atmosphere.
