PPS01-01

Room:A03

Time:May 26 12:00-12:15

Numerical Modeling of Moist Convection in Jovian Planets
SUGIYAMA, Ko-ichiro1∗ ; NAKAJIMA, Kensuke2 ; ODAKA, Masatsugu2 ; KURAMOTO, Kiyoshi2 ;HAYASHI, Yoshi-yuki4
1

ISAS/JAXA, 2 Kyushu University, 3 Hokkaido University, 4 Kobe University

It is now widely accepted that moist convection is a common phenomenon in Jovian planets’ atmosphere. The moist convection is thought to play an important role in determining the mean vertical structure of the atmosphere; the mean vertical profilesof temperature, condensed components, and condensible gases in the moist convection layer is thought to be maintained by thestatistical contribution of a large number of clouds driven by internal and radiative heating/cooling over multiple cloud life cycles.
However, the averaged structure of the Jovian planets’ atmosphere and its relationship to moist convection remain unclear. For
the purpose of investigating the above problem, we developed a cloud resolving model and investigated a possible structure ofmoist convection layer in Jupiter’s atmosphere with using the model (Sugiyama et al., 2009, 2011, 2014). In this presentation,
we perform two-dimensional calculations of moist convection and demonstrate a possible structure in the atmospheres of Saturnand Uranus.
The basic equation of the model is based on quasi-compressible system (Klemp and Wilhelmson, 1978). The cloud microphysics is implemented by using the terrestrial warm rain bulk parameterization that is used in Nakajima et al. (2000). We
simplify the radiative process, instead of calculating it by the use of a radiative transfer model. The model atmosphere is subject
to an externally given body cooling that is a substitute for radiative cooling. Because the vertical profile of net radiative heating is
not observed in Saturn and Uranus, the layer between 2 bar level and the tropopause, which corresponds to the observed coolinglayer in Jupiter, is cooled. The body cooling rate is set to be 100 times larger than that observed in Jupiter’s atmosphere in orderto save the CPU time required to achieve statistically steady states of the model atmosphere. The domain extends 7680 km in
the horizontal direction. The vertical domains of the planets are 480 km for Saturn’s case and 650 km for Uranus’ case. The
spatial resolution is 2 km in both the horizontal and the vertical directions. The temperature and pressure at the lower boundary
are based on the one-dimensional thermodynamical calculation (Sugiyama et al., 2006). As the first step of the experiments, theabundance of each condensable gas is set to be solar abundance.
In Saturn and Uranus, the obtained characteristic of vertical motion is that many narrow and strong downdrafts are found in theupper moist convection layer, while strong updrafts are found near the bottom of the moist convection layer that is associated with
the H2O lifting condensation level. This characteristic is obviously different from that obtained in Jupiter. The vertical motion in
the whole moist convection layer of Jupiter is characterized by narrow, strong, cloudy updrafts and wide, weak, dry downdrafts.
In Saturn and Uranus, the velocity of downdrafts is over 50 m/s, which is comparable to the updrafts, and the skewness of verticalvelocity is negative in the upper moist convection layer. The skewness obtained in Uranus’ case is the smallest, which indicatesthe downdrafts are more dominant in Uranus than in Saturn. The existence of strong downdrafts is caused by the following two
reasons. One of the reasons is that convective motion is driven by not a heating from the bottom of the moist convection layer
but a cooling layer near the tropopause (0.1 <p <2 bar). Another reason is that the atmospheric temperature in the upper moist
convection layer is colder than that of Jupiter. H2O condensation occurs at lower level (high pressure level). The value of H2O
mixing ratio is almost zero and the effect of latent heat is very small in the upper part of the layer.
Keywords: atmosphere of Jovian planets, moist convection, numerical modeling, cloud resolution model

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PPS01-02

Room:A03

Time:May 26 12:15-12:30

The radiative cooling and the solar heating in Jovian troposphere
TAKAHASHI, Yasuto1∗ ; HASHIMOTO, George3 ; ISHIWATARI, Masaki1 ; TAKAHASHI, Yoshiyuki O.2 ;SUGIYAMA, Ko-ichiro4 ; ONISHI, Masanori2 ; KURAMOTO, Kiyoshi1
1

Hokkaido University, 2 Kobe University, 3 Okayama University, 4 ISAS

For Jupiter, the atmospheric energy balance is important to understand not only its characteristic atmosphere circulation but
also the thermal history over 4.5 Ga. To estimate effects of solar heating and thermal radiation cooling, radiative transfer models
are useful. Some previous studies discussed the heating rate in the stratosphere in order to analyze the mechanism of thermal
inversion layer formation (Yelle et al., 2001), whereas that in troposphere has been little treated because the temperature profile
can be simply explained by the adiabatic profile. However, the tropospheric thermal balance must be important because thisregion emits the major part of Jovian thermal radiation and allows cloud activities by generating the convective instability.
So far, we have been developing a radiative-convective equilibrium model to calculate the thermal structure of H2 -rich atmosphere. By using this model, here we examine how major condensable gases (H2 O, CH4 , NH3 ) and isolation affect thecooling rate profile in jovian troposphere. For this purpose, we solve 1-D radiative transfer equation in a plane-parallel, non-gray,cloud-free atmosphere over 0-25,000cm−1 which covers both the planetary radiation and solar radiation. H2 -He collision induced absorption (Borysow 1992, 2002), H2 O, CH4 , NH3 , PH3 , H2 S and GeH4 line absorptions (HITRAN2012), and Rayleighscattering are considered as optical parameter. Canonical mixing ratios of these heavy species are given as three times the solar
abundance, respectively. Depletion of condensable species due to condensation is also taken into account.
From our results, we found that the cooling is strongly affected by thermal emission from gaseous NH3 associated with slightcontribution from H2 and He. The cooling rate profile shows a peak around 0.59 bar and its value is -2.3x10−7 K/sec. The
calculation without NH3 shows peak (-6.6x10−8 K/sec) around 0.8bar. H2 O and CH4 have little contribution in upper troposphere, but their contribution increase in deep atmosphere (below 1bar). Solar radiation with wave number between 2,500-10,000
cm-1 (wavelength of 1-4 micron meter) significantly heats stratosphere, but its effect becomes weaker as pressure increases, thenalmost vanishes below 1 bar level. Solar radiation with higher wave number between 10,000-25,000 cm−1 (0.4-1 micron meter)
almost uniformly heats the stratosphere (7.1x10−8 K/sec) and its effect also becomes weaker in the deep atmosphere. Those
heating compensate the radiative cooling, and change the sign of heating rate from minus to plus below 1.2 bar level.
These results show that the cooling in troposphere is virtually dominated by NH3 . One might consider that our estimation
depends on the abundance of NH3 in the deep atmosphere, which is not well constrained at present. But the atmospheric cooling
occurs basically in the upper troposphere where the NH3 abundance follows the saturation vapor pressure curve. Therefore,
the uncertainty in NH3 abundance in deep atmosphere may have a limited effect on the cooling profile in troposphere. Moresignificant factor may be the abundance of H2 S relative to NH3 . It is expected to be 1/3 if we assumed solar abundance, but theactual abundance is poorly constrained especially for H2 S. If the ratio becomes higher, the cooling rate profile is greatly changed
because of loss of NH3 gas owing to NH4 SH formation. It indicates that unknown H2 S abundance is an important factor that
controls not only NH4 SH cloud formation but also convective activities in the upper troposphere.
Keywords: Jupiter, radiative transfer, thermal equilibrium, troposphere, cooling rate

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PPS01-03

Room:A03

Time:May 26 12:30-12:45

Simulation study of Jupiter’s stratosphere: development of a new radiation code and impacts on the dynamics
KURODA, Takeshi1∗ ; MEDVEDEV, Alexander S.2 ; SETHUNADH, Jisesh2 ; HARTOGH, Paul2
1

Planetary Plasma and Atmospheric Research Center, Tohoku University, 2 Max Planck Institute for Solar System Research

We have developed a new radiation code of radiative heating and cooling for Jupiter’s upper troposphere and stratosphere (103
to 10−3 hPa) suitable for general circulation models (GCMs). It is based on the correlated k-distribution approach, and accounts
for all the major radiative mechanisms in the Jovian atmosphere (heating due to absorption of solar radiation by CH4 , and coolingin the infrared by C2 H6 , C2 H2 , CH4 and collision-induced transitions of H2 -H2 and H2 -He). The code can be applied for Saturnand extrasolar gas giants. Vertical 1-D calculations using this code demonstrated that temperature of Jupiter’s stratosphere isclose to radiative-convective equilibrium, and that the radiative relaxation time decreases exponentially with height (from 108 s
near the tropopause to 105 s in the upper stratosphere). The latter differs from the study of Conrath et al. (1990), which showed
the very long (∼108 s) relaxation time approximately constant throughout the stratosphere. Our calculations with the GCM
show that the radiative relaxation time suggested by Conrath et al. (1990) is too long, and cannot sustain convergence of model
solutions. With the newly derived vertical profile of relaxation time, simulations converge and produce realistic temperature andwind in Jovian stratosphere.
Keywords: Jupiter, Stratosphere, Atmospheric radiation, Atmospheric dynamics, Gas giants, JUICE

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PPS01-04

Room:A03

Time:May 26 14:15-14:35

Cassini-Huygens Mission Highlights: Discoveries in the Saturn System
SPILKER, Linda1∗ ; EDGINGTON, Scott1 ; ALTOBELLI, Nicolas2
1

Jet Propulsion Laboratory/California Institute of Technology, Pasadena, CA, USA, 2 ESA/ESAC, Villafranca del Castillo,
Madrid, Spain
Cassini-Huygens exploration of the Saturn system has yielded 11 years of unprecedented discoveries, and answers to many
scientific mysteries. Cassini’s findings have revolutionized our understanding of Saturn, its complex rings, its amazing assortment of moons and the planet’s dynamic magnetic environment. The robotic spacecraft arrived in 2004 after a 7-year flightfrom Earth, dropped a parachuted probe named Huygens to study the atmosphere and surface of Saturn’s big moon Titan, andcommenced making astonishing discoveries that continue today.
Among its many firsts, Cassini discovered cryovolcanic jets shooting from the south pole of the tiny moon Enceladus; foundhydrocarbon lakes and seas on Titan that are dominated by liquid ethane and methane as well as complex pre-biotic chemicals
form in the atmosphere and rain to the surface; provided multi-wavelength coverage of a giant northern storm, the first of its kindon Saturn since 1990; demonstrated that the Saturn Kilometric Radiation period does not reflect the planet’s internal rotation;
proved that Enceladus is the source of Saturn’s E Ring and that its water dominates the magnetosphere; and constrained andcomplicated our understanding of the 3-dimensional structure and dynamics of multi-particle ring systems. Cassini’s findings at
Saturn have also fundamentally altered many of our concepts of how planets form around stars.
In just the last two years, Cassini discovered that: the majority of Titan’s lakes and seas are located near the north pole andmeasured the depths of some of the seas; Enceladus harbors a subsurface ocean; a huge hurricane rages at Saturn’s north pole;
tidal stresses control Enceladus’ particulate jets; plume activity is greatest near apoapse; the depth of Titan’s Ligeia Mare is150-200 meters; meteorite impacts, embedded propellers migrating inwards and outwards, and the effects of Saturn internal oscillations can be witnessed in the rings; Titan has a subsurface water ocean; interactions between a strong solar wind and Saturn’smagnetosphere can help us understand supernovae shockwaves; and Titan’s south polar haze is a seasonal phenomenon.
The Solstice Mission continues to provide fundamental new science as Cassini observes seasonal and temporal changes, andaddresses new questions that have arisen during the mission thus far. The mission’s grand finale occurs in 2017, with 22 inclined
orbits between the innermost D ring and the upper portions of Saturn’s atmosphere, enabling unique gravity and magnetic fieldmeasurements of the planet, unprecedented determination of the ring mass, some of the highest resolution measurements of therings and Saturn, and in situ observations in a completely new region around the planet. Highlights from 11 years of Cassini’s
ambitious inquiry at Saturn will be presented along with the remarkable science that will be collected in the next three years.
Cassini-Huygens is a cooperative undertaking by NASA, the European Space Agency (ESA), and the Italian space agency(Agenzia Spaziale Italiana, ASI).
This work was carried out in part at the Jet Propulsion Laboratory, California Institute of Technology, under contract with
NASA. Copyright 2015 California Institute of Technology. Government sponsorship is acknowledged.
Keywords: Cassini, Saturn, Huygens, Rings, Titan

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PPS01-05

Room:A03

Time:May 26 14:35-14:50

Cassini Imaging Science at Saturn: Global Atmospheric Dynamics and Cloud Morphology
SAYANAGI, Kunio1∗ ; INGERSOLL, Andrew P.2 ; DYUDINA, Ulyana A.2 ; EWALD, Shawn P.2 ;BLALOCK, John J.1
1

Hampton University, 2 California Institute of Technology

We present recent results produced by the ISS visible-wavelength imaging camera onboard the Cassini spacecraft, which has
been orbiting Saturn since 2004. The atmosphere of Saturn is not static. Just like that of Earth, it harbors many phenomena witha wide range of timescales that evolve over time. Our presentation will first present a mean-state of Saturn using a global mosaic
of Saturn. The cloud features of Jupiter are well-characterized due to the stark contrast presented by light and dark bands, theGreat Red Spot, and other discrete vortices. In comparison, Saturn?fs cloud bands and features are more muted due to the thickglobal stratospheric haze layer that masks the tropospheric clouds. In addition, we emphasize that, because the rings and ringshadows obscures much of the winter planet, global maps of Saturn can be obtained only from the vantage point of an orbiting
spacecraft. Using the images of Saturn obtained before and after the equinox of 2009, we have constructed global cloud mosaics
of Saturn. We also present temporal evolution of the zonal wind profile between 2005 and 2013.
We will first give a global overview of cloud features on Saturn that has been observed by Cassini and then focus on individual
regions of interest. Among the many cloud features, we focus on the following. The first feature we will report on is the changes
exhibited by the region where the Great Storm of 2010-2011 erupted. The disturbance left behind the storm continues to evolve,
and we present the latest update. Second, we present the morphology of the north polar region. The hexagonal cloud feature
at 75 degree N latitude emerged from the winter shadow in 2008, and its morphology fully came into view after the equinox in2009. The cloud contrast has been evolving with seasons, and we present our observation. We also report our observation of thenorth-polar vortex, and compare that to its southern counterpart.
Our study is supported by the Cassini Project, NASA Outer Planet Research Program grant NNX12AR38G, NASA Planetary
Atmospheres grant NNX14AK07G, and NSF Astronomy and Astrophysics grant 1212216.
Keywords: Planetary Science, Jovian Planet, Saturn, Cassini Mission, Atmosphere, International Cooperation

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PPS01-06

Room:A03

Time:May 26 14:50-15:05

Exploration of Titan’s Seas
LORENZ, Ralph1∗
1

JHU Applied Physics Laboratory

Saturn ′ s moon Titan has extensive lakes and seas of liquid hydrocarbons that are a priority target of future exploration. The
largest of these seas, Ligeia Mare and Kraken Mare, are ∼400km and ∼1000km in extent, respectively, and are composed ofliquid methane and ethane at 94K, with likely traces of hundreds of other organic compounds. Titan’s seas represent a laboratory
for air-sea exchange and other hydrological and oceanographic processes, as well as a site of astrobiological interest.
Observations from the Cassini spacecraft, in particular its radar instrument, have measured the depth of Ligeia Mare to be∼160m, consistent with terrestrial basins of similar size. The tidal amplitudes have been predicted to be some tens of centimeters,
and as surface windspeeds grow to 1-2m/s as we approach northern summer in 2017, waves are expected to form. Cassini
observations of sunglint and with radar and radio generally show the sea surface to be flat up to now, but some time-variable
patches of reflectivity show that dynamic processes are active, and perhaps that waves are just beginning to form. Further Cassini
observations are eagerly anticipated.
Several proposals have considered future missions to Titan’s seas. Of these, the most detailed work was for a NASA Discovery
Phase A study, the Titan Mare Explorer, TiME. This envisaged a radioisotope-powered capsule in Ligeia Mare in 2023, which
it would traverse over several weeks blown by the wind. Detailed designs and operations plans were developed, and prototype
instrument systems (e.g. sonar transducers, liquid sampling inlets) tested in cryogenic conditions; scale model splashdown testing
was also performed.
More recently, the NASA Institute for Advanced Concepts has sponsored a study of a robot submarine to explore Titan ′ sseas circa 2040. This study has addressed some unique challenges such as the reconciliation of hydrodynamic design drivers
with the need to accommodate a large data relay antenna.
Whether these vehicles, or other systems such as airplanes or balloons, explore Titan next, it is clear that Titan’s seas offer
tremendous scientific potential and public engagement.

Keywords: Titan, Hydrocarbons, Oceanography, Exploration Vehicles, Radar

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PPS01-07

Room:A03

Time:May 26 15:05-15:25

JUICE: A EUROPEAN MISSION TO JUPITER AND ITS ICY MOONSBRANDT, Pontus1∗ ; WITASSE, Olivier2 ; TITOV, Dmitri2 ; ALTOBELLI, Nicolas2 ; BARABASH, Stas3 ;BRUZZONE, Lorenzo4 ; BUNCE, Emma5 ; COUSTENIS, Athena6 ; DOUGHERTY, Michele7 ; ERD, Christian2 ;FLETCHER, Leigh8 ; GLADSTONE, Randy9 ; GRASSET, Olivier10 ; GURVITS, Leonid11 ; HARTOGH, Paul12 ;HUSSMANN, Hauke13 ; IESS, Luciana14 ; LANGEVIN, Yves15 ; PASQUALE, Palumbo16 ; PICCIONI, Guiseppe17 ;PLAUT, Jeffrey18 ; RETHERFORD, Kurt9 ; WAHLLUND, Jan-erik19 ; WURZ, Peter20
1

The Johns Hopkins University Applied Physics Laboratory, 2 ESTEC, The Netherlands, 3 The Swedish Institute of Space Physics,
Kiruna, Sweden, 4 Universita degli Studi di Trento, Italy, 5 University of Leicester, United Kingdom, 6 Observatoire de Meudon,
France, 7 Imperial College London, United Kingdom, 8 University of Oxford, United Kingdom, 9 Southwest Research Institute, San Antonio, TX, USA, 10 Universite de Nantes, France, 11 Joint Institute for VLBI in Europe, The Netherlands, 12 MaxPlanck-Institut fur Sonnensystemforschung, Germany, 13 DLR, Institut fur Planetenforschung, Germany, 14 Universita di Roma
La Sapienza, Italy, 15 Institut d’Astrophysique Spatiale, France, 16 Universita degli Studi di Napoli Parthenope, Italy, 17 Istituto di
Astrofisica e Planetologia Spaziali - Istituto Nazionale di Astrofisica, Rome, Italy, 18 Jet Propulsion Laboratory, Pasadena, CA,
USA, 19 The Swedish Institute of Space Physics, Uppsala, Sweden, 20 University of Bern, Bern, Switzerland
The recently adopted European Space Agency (ESA) mission JUpiter ICy moon Explorer (JUICE), the first large mission selected by ESA within the Cosmic Vision 2015-2025 Programme, is currently planned for launch in 2022. Details of the mission
are described, including the payload, planned orbits and the expected science return. The focus of JUICE is to characterise theconditions that may have led to the emergence of habitable environments among the Jovian icy satellites, with special emphasison the three worlds, Ganymede, Europa, and Callisto, likely hosting internal oceans. Ganymede, the largest moon in the Solar
System, is identified as a privileged target because it provides a natural laboratory for analysis of the nature, evolution and potential habitability of icy worlds in general, but also because of the role it plays within the system of Galilean satellites, and its
unique magnetic and plasma interactions with the surrounding Jovian environment. The mission also focuses on characterising
the diversity of coupling processes and exchanges in the Jupiter system that are responsible for the changes in surface, ionosphericand exospheric environments at Ganymede, Europa and Callisto from short-term to geological time scales. Focused studies ofJupiter’s atmosphere and magnetosphere, and their interaction with the Galilean satellites will further enhance our understandingof the evolution and dynamics of the Jovian system.
Keywords: Jupiter, Ganymede, Europa, Callisto, Magnetosphere

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PPS01-08

Room:A03

Time:May 26 15:25-15:40

Jupiter Icy Moons Explorer: JUICESAITO, Yoshifumi1∗ ; SASAKI, Sho2 ; FUJIMOTO, Masaki1
1

Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 2 Department of Earth and Space Sciences,
School of Science, Osaka University
JUICE is an ESA’s L-class mission to Explore Jupiter Icy Moons. JUICE was mission adopted in November 2014. It will belaunched in 2022, arrive at Jupiter in 2030 and be inserted into Ganymede orbit in 2032. The science objectives of JUICE is
to understand (1) emergence of habitable worlds around gas giants and (2) Jupiter system as an archetype for gas giants. ThreeJapanese groups were selected to provide part of the three science instruments RPWI, GALA, and PEP/JNA. Two Japanese groups
were also selected as science Co-I of two instrument groups JANUS and J-MAG. JUICE is the first mission for ISAS/JAXA toparticipate to foreign large science mission as a junior partner who will provide part of the science instruments. JUICE willobserve Jupiter system from Jupiter orbit in order to understand Jupiter system as an archetype for gas giants. JUICE will
make observation of 3 of the 4 Galilean satellites, Europa, Ganymede, and Callisto in order to understand the emergence ofhabitable worlds around gas giants. JUICE will be launched by Arian-5. The Dry mass of JUICE is about 1800kg and the fuelis about 2900kg. The required Delta-V is about 2700m/s. JUICE is a three-axis stabilized spacecraft with solar cell paddle ofabout 70m2 that will generate approximately 700W power. The mass and power allocated to science instrument is 104kg and
150W, respectively. X band and Ka band are used for satellite-ground communications. After 7.5 years of interplanetary transfer
and Earth-Venus-Earth-Earth gravity assists JUICE will be inserted into an orbit around Jupiter in January 2030. JUICE will
make observation of all the three Jupiter icy Moons that potentially have subsurface ocean under the icy crust. After inserted
into Ganymede orbit in 2032, JUICE will make detailed observation of the largest Icy Moon in the solar system. Taking into
account all the data to be obtained by 5 instruments that JUICE-JAPAN will participate, Japanese team will be able to contributeto most of the major science objectives relating with planet Jupiter (JANUS), Jupiter magnetosphere (PEP/JNA, RPWI, andJ-MAG), and Icy Moons (GALA, J-MAG, and JANUS). JUICE-JAPAN Working Group (WG) was established in September
2013. JUICE-JAPAN WG submitted a proposal for ISAS/JAXA small project in February 2014. JUICE-JAPAN WG passed the
MDR in September 2014. JUICE-JAPAN is now preparing for the SRR. After SRR, SDR is scheduled in the end of 2015, PDR
is scheduled in 2016 and CDR is scheduled in 2017.

Keywords: Jupiter, Ganymede, Satellite Exploration

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PPS01-09

Room:A03

Time:May 26 15:40-15:55

Outer Planet Exploration by the Solar Power Sail: Cruising Observation and In-situ Investigation of Jupiter Trojans
YANO, Hajime1∗ ; MATSUURA, Shuji1 ; NAKAMURA, Ryosuke2 ; YONETOKU, Daisuke3 ; KEBUKAWA, Yoko4 ;AOKI, Jun5 ; MORI, Osamu1 ; SOLAR POWER SAIL, Working group1
1

Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 2 National Insitute of Advanced Science andTechnology, 3 Kanazawa University, 4 Yokohama National University, 5 Osaka University
After more than a decade of mission studies and front loading technology developments and verifications including IKAROS,
the first deep space solar sail in the history, the Solar Power Sail mission has been proposed to JAXA/ISAS in February 2015, asa candidate of the upcoming strategic middle-class mission for a space engineering-driven mission to demonstrate the first outer
Solar System exploration of Japan.
While demonstrating the solar power sail technology in the deep space at 1-5.2 AU, it is bound to Jupiter Trojan asteroids,
which may hold fundamental clues of the Solar System formation and revolution discussed by two competing hypotheses between the classic model and the planetary migration model. The former suggests that Trojan asteroids are mainly survivors ofbuilding blocks of the Jupiter system, while the latter claims that they must be intruders from outer regions after the planetary
migration of gas planets settled.
Right after the launch around 2021, the cruising observation will start to produce scientific results. First dust-free infrared
astronomical observation beyond the zodiacal light foreground scattering will be conducted to search for the first generation lightof the Universe, let alone optical observation of the zodiacal light structure of the Solar System. Extremely long baseline withthe observation from the Earth, gamma-ray burst observation can identify their sources. Continuous dust impact detection will
reveal the large structure and distribution of the Solar System dust disk by >4 mˆ2 of an large-area dust detector array deployedon the sail membrane.
After Jupiter flyby, the spacecraft will reach to a target Trojan asteroid of >20 km in size in 2030s. Both global remote observation and deployment of an autonomous lander will be conducted. On the surface of the Trojan asteroid, sampling will be
attempted for in-situ TOF mass spectrometry and passing the sample container to the mothership for a possible sample return
option.
This presentation discusses major scientific objectives, mission design and spacecraft system of the solar power sail, together
with current development status, in-situ observation instruments and including landing and sample return from the surface of a
Trojan asteroid.
Keywords: Solar Power Sail, Cruising Observation, Jupiter Trojan Asteroids, Surface Exploration, In-situ Mass Spectrometry,
Sample Return

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PPS01-10

Room:A03

Time:May 26 16:15-16:30

Tidal deformation of Ganymede and effects of a subsurface ocean: a model calculation in
preparation for JUICE
KAMATA, Shunichi1∗ ; KIMURA, Jun2 ; MATSUMOTO, Koji3 ; NIMMO, Francis4 ; KURAMOTO, Kiyoshi1
1

Hokkaido Univ., 2 ELSI/Tokyo Tech., 3 NAOJ, 4 UC Santa Cruz

One of major objectives of the JUICE (JUpiter Icy moons Explorer) mission is to characterize the extent of subsurface oceans of
the moons, in particular Ganymede, and GALA (GAnymede Laser Altimeter) is planned to detect and monitor tidal deformation,
which is sensitive to the interior structure. A previous study indicates that the viscosity of the icy shell is the major controlling
factor of the amplitude of tidal deformation [Moore and Schubert, Icarus , 2003]. This result, however, is based on simple
calculation results assuming a shell with uniform viscosity. For a conductive shell, the actual viscosity will depend strongly on
depth; the viscosity is very high at a shallow depth and is low at the base of the shell; such a large variation in viscosity should
affect tidal deformation. Thus, a detailed investigation for tidal deformation of Ganymede in light of a depth-dependent viscosity
is necessary prior to the JUICE mission. In this study, we investigate the amplitude and the phase lag of tidal deformation ofGanymede assuming a depth-dependent viscosity shell model.
Preliminary results assuming a constant temperature gradient and an Arrhenius-type rheology suggest that the main control
on tidal deformation is not reference viscosity (i.e., viscosity at the melting temperature) but is rigidity if the subsurface ocean
is thick (>10 km). For a conductive shell the fluid limit of tidal deformation is unlikely to be achieved even if the reference
viscosity is extremely low (i.e., 1010 Pa s) because of the high viscosity near the surface. The thickness of the ocean is foundto be a minor control as long as a subsurface ocean exists. The phase lag can be up to several degrees, though the range of its
variation for a depth-dependent viscosity model is much smaller than that for a uniform model. These results indicate that thepresence of a high-viscosity near-surface layer, which has been ignored previously, has a large effect on tidal deformation on
Ganymede.
On the other hand, if a subsurface ocean does not exist, the major control on tidal deformation is the viscosity of a high-pressure(HP) ice layer; the near-surface layer plays a minor role in contrast to a thick ocean case. If a HP ice layer has an extremely low
viscosity (˜1012 Pa s), such a layer behaves as fluid, leading to amplitude and phase lag similar to those for a thick ocean case. If
a HP ice layer has a moderate or high viscosity, the tidal Love number h2 would be <0.5, which is much smaller than that for a
thick ocean case (i.e., h2 >1). GALA measurements should distinguish such a difference in tidal amplitude.
Keywords: Tidal deformation, Ganymede, Subsurface ocean, JUICE, GALA

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PPS01-11

Room:A03

Time:May 26 16:30-16:45

Interior evolution of Ganymede and its surface manifestation: toward JUICE measurements
KIMURA, Jun1∗ ; KURAMOTO, Kiyoshi2
1

Earth-Life Science institute, Tokyo Tech, 2 Hokkaido University

Jovian moon Ganymede is the largest moon in our solar system and its icy surface is shared by global-scaled tectonics, termed
as grooved terrain, which has been interpreted as grabens resulting from lithospheric extension and the average impact crater
density on the grooved terrain corresponds to an age of 2 Gyr. According to geological estimates, 3-4% increase in the satellite
radius may be required for their formation. In addition, the small value of the moment of inertia factor and the strong intrinsic
magnetic field observed for Ganymede are consistent with a highly differentiated interior with a conductive dense core. Hence
Ganymede has likely undergone significant temperature rise inside allowing the separation of a conductive core and global expansion during its history. However, the release of accretional energy is insufficient for the melting of metallic materials. Either the
short-lived radio nuclides or the late stage heavy bombardment should heat the interior too early to explain the global expansion
at 2 Ga from the formation of Ganymede. Thus its mechanisms still remain an open question.
This study numerically investigates the possible influence of hydrated rock on the thermal history of Ganymede. Here weassumes that Ganymede had an initial structure with a relatively thin water ice mantle and a low temperature primordial coremade of the mixture of hydrous rock and Fe-sulfide similar to hydrated primitive meteorites. This may be supported in part by thesimilarity in reflectance spectra among hydrated carbonaceous chondrites and asteroids near Jovian orbit. In order to investigate
above influence, we perform numerical simulations for the internal thermal evolution using a spherically symmetric model forthe convective and conductive heat transfer with radial dependence of viscosity and heat source distribution. The primordialcore is heated by the decay of long-lived radioactive nuclides. The rise of core temperature is kept slow after the occurrenceof effective thermal convection in the core having low viscosity of hydrous rock. However, once the temperature reaches thedehydration point then the highly viscous, anhydrous region begins to grow associated with the release of water to the mantle.
The core temperature thereby becomes to increase faster with accelerating the further dehydration of primitive matter. Dehydration of serpentine occurs at 1 to 2 Gyr after the satellite formation, giving an explanation for the cratering age of grooved
terrain, and increasing in total volume of the moon by the dehydration is expected from calculation of temperature, pressure, anddensity with depth profiles extending from the center to the surface of the moon using 3rd-order Birch-Murnaghan equation ofstate with the thermal effect incorporated into the thermal expansion coefficient. In addition, the core temperature subsequently
exceeds the eutectic point of the Fe-bearing sulfide and oxide so that the formation of a conductive dense core could occur by
their gravitational segregation. Meanwhile, Callisto does not heat up sufficiently to melt the sulfide component or dehydrate theprimordial core because of the efficient heat loss for smaller body. The difference of radiogenic heat and moon’s size between
Ganymede and Callisto may have potential to create the surface and interior dichotomy between two moons.
Finally, we expect these hypothesis can be validated through the JUICE mission. Coverage and resolution of current data for
Ganymede’s surface acquired by Voyager and Galileo spacecraft are quite poor, and considerable part of the surface has beenclassified as ’unclassified unit’ in the current geologic map. GALA and JANUS onboard JUICE spacecraft will perform a fullglobal mapping of surface morphology of Ganymede, thus we will be able to constrain an amount of surface area increment
associated with the groove formation and a regional surface age of each groove to see a tectonic history and interior evolution.

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PPS01-12

Room:A03

Time:May 26 16:45-17:00

Geophysical Controls on the Habitability of Icy Worlds: Focus on Europa
VANCE, Steven1∗ ; HAND, Kevin1 ; PAPPALARDO, Robert1
1

Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA

Many icy worlds in the solar system are likely to contain inventories of liquid water comparable to Earth’s. This meets only
one planetary habitability requirement; less is known about whether icy world oceans permit the needed chemical disequilibria.
Evidence for sustained internal heat and abundant water on Jupiter’s moon Europa suggest life would have had the perceived
time necessary to develop there, but sources of electron donors and acceptors critical for habitability have been difficult to assess.
Past investigations assumed hydrogen production at the rock-ocean interface scales with the heat input to the rocky interior, andthat subsurface weathering and alteration are inconsequential. However, estimates of hydrogen production rates on Earth showthat low-temperature hydration of crustal olivine produces substantial hydrogen, on the order of 1011 moles yr−1 , comparable
to the flux from volcanic activity. Here, we estimate global average rates of water-rock reaction on Earth, Mars, and icy worlds
in the solar system using the pressure- and temperature-dependent physics of microfracturing in olivine. We predict hydrogenproduction within Europa’s oceanic crust—also potentially applicable to other icy worlds—that are higher than those on Earth,even in the absence of contemporary high-temperature hydrothermal activity. Radiogenic cooling exposes unweathered rocky
material progressively over time to ever greater depths. Shallower gradients in pressure and temperature in objects smaller than
Earth expose new unaltered rock with an efficiency that scales as the inverse of gravity, so up to 100x more efficiently than Earth.
Weathering and alteration of exposed material, mainly by serpentinization, release heat and hydrogen, which are necessary forlife. We hypothesize that Europa’s ocean could have become reducing during geologically brief periods when hydrogen flux fromrapid reweathering far exceeded oxidant flux. thermal-orbital resonance 2 Gyr after Europa’s accretion that caused oscillations
in mantle heating. Europa’s present-day limit of mantle tidal heating would produce volcanic hydrogen (0.6-2x1010 moles yr−1 )that offsets the low end of estimated production from serpentinization alone (total range 4x108 -5x1010 moles yr−1 ). Evidence
for subduction- like behavior in Europa’s ice suggests that radiolytic oxidant flux to its ocean is at that high end of the previously
estimated range (5x109 -4x1011 moles yr−1 ). These factors make Europa unique among icy worlds for potentially having an
oxidizing ocean with a high flux of reductants. Europa is thus a prime candidate for hosting life.
Keywords: Europa, Icy Worlds, Astrobiology, Habitability, Outer Planets, Microfracturing

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PPS01-13

Room:A03

Time:May 26 17:00-17:15

Application of Habitable Trinity concept to Europa
MARUYAMA, Shigenori1∗
1

Eearth-Life Scienece InstituteHabitable Trinity is one of the most significant condition to bear life. Habitable Trinity is the environment where atmosphere,
ocean, and landmass coexist under the driving force for material circulation between trinity components. Habitable Trinity
condition is the minimum requirements to emerge life. Because life body is not made from only water component. Life needs
constant supply of C, H, O, N and minor elements derived from landmass such as P,K, Fe etc to maintain the body. Therefore
Habitable Trinity environment is the key for life.
This requirement can be applied to other planetary bodies in the Universe. Let’s think about the case of Europa, the moonof planet Jupiter. Europa has a water-ice crust on its surface and thought to have water ocean beneath it. People who think theexistence of liquid water enable life be emerged insist that there is life in Europa due to the existence of water ocean under the icy
crust. Once we consider the conditions of Europa based on Habitable Trinity concept, the answer is given easily, which means
there is no chance to bear life on Europa. Europa does not provide the environment to maintain coexistence of atmosphere, ocean,and landmass which is constantly circulated.

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PPS01-14

Room:A03

Time:May 26 17:15-17:30

ENERGETIC NEUTRAL ATOM (ENA) IMAGING OF THE EUROPA GAS CLOUD
FROM JUICEBRANDT, Pontus1∗ ; MITCHELL, Donald1 ; WESTLAKE, Joseph1 ; MAUK, Barry1 ; SMITH, Todd1
1

The Johns Hopkins University Applied Physics Laboratory, Laurel, MD, USA

The Jupiter Energetic Neutrals and Ions (JENI) Camera is one out of six sensors of the Particle Environment Package (PEP)suite that was selected for flight on the ESA Jupiter Icy Moon Explorer (JUICE). JENI is a combined imaging energetic ion
spectrometer and an ENA camera that operates in the ∼0.5 keV to 1 MeV range for ions and ∼0.5 ? 500 keV for ENAs and iscapable of separating H, O, and S. Its angular resolution is ≤2 ⁰ for ≥10 keV H.
In ENA mode JENI’s main objective is to constrain the Europa surface (or subsurface) mechanisms that release material tospace by imaging the neutral gas surrounding Europa using ENAs produced when energetic ions of the Jovian magnetospherecharge exchange with the extended neutral gas atoms or molecules.
ENA observations of Jupiter by the Ion and Neutral Camera (INCA) the Cassini spacecraft have revealed ENA emissions
surrounding Jupiter at about the orbital distance of Europa. The observations are consistent with a column density peaking
around Europa’s orbit in the range from 2×1012 cm−2 to 7×1012 cm−2 , assuming H2 , and are consistent with the upper limits
reported from the Cassini/UVIS observations. Detailed analysis shows indications that the neutral gas cloud may be centeredon Europa and not symmetric around Jupiter. This would directly imply that the source of the gas is Europa itself. The INCA
observations also show indications of magnetospheric dynamics that result in about a factor of two variation in ENA intensity.
We describe the INCA observations and its implications for JUICE, Juno and Europa Clipper, and discuss the neutral-plasma
coupling pertinent to the Europa/Io plasma/neutral environment.

Keywords: Europa, Jupiter, Torus, Magnetosphere

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PPS01-15

Room:A03

Time:May 27 09:00-09:20

Solar System Satellite Formation : an overview
CHARNOZ, Sebastien1∗
1

Institut de Physique du Globe de Paris (IPGP), 2 AIM (Astrophysique Instrumentation Modelisation)

The origin of Solar System satellites is actively debated. We know understand that, despite the morphological analogy between
a satellite system and a planetary system, the formation processes of satellites may be significantly different from planetary
formation processes. in addition, satellites evolve quickly under the effects of tides. Different scenarios seem to be required for
different types of planets (terrestrial, giant or ice giant). In this talk I will current satellite formation models and the different
constrains. Based on Cassini images and numerical simulation, I will show that there is today on-going accretion processes atthe edge of Saturn’s rings, pointing to a new satellite formation process.
Keywords: Planet, Satellites, Formation

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PPS01-16

Room:A03

Time:May 27 09:20-09:40

The Juno Mission and the Role of Earth-Based Supporting Observations
ORTON, Glenn1∗
1

Jet Propulsion Laboratory, California Institute of Technology

The Juno spacecraft was launched in 2011 and passed close to the Earth for a gravity assist in 2013. It will reach Jupiter inJuly of 2016 and enter orbit around Jupiter, with the first of over thirty highly elliptical polar orbits whose periapsis distances
are inside the radiation belts. The purpose of the mission is to determine the abundance and distribution of water in the deep
atmosphere of Jupiter, map the close-in gravity field, and map the electromagnetic environment over all longitudes. These
investigations will determine the structure, composition and dynamics of the interior of Jupiter. It will relate features that areeasily detectable in the exterior of Jupiter to movement in the deep interior. Understanding these processes will provide clues toformation and evolution of Jupiter, providing insight into the formation of giant planets in general. The complement of scientificinstruments on board Juno consists of in-situ instruments that measure the electromagnetic environment of Jupiter and remotesensing instruments that cover a broad, but incomplete, spectral range. The Ultraviolet Spectrometer (UVS) will cover 70-205
nm, the Juno IR Auroral Mapper (JIRAM) will cover 2-5 µm, and the Microwave Radiometer (MWR) will cover 1.3-50 cm.
In addition, a public-outreach camera, JunoCam, will produce images in broad-band red, green and blue filters, together witha narrow-band 890-nm filter centered on a CH4 gaseous absorption feature. Juno will make over thirty orbits of Jupiter, butremote sensing will only be a priority on orbits 1 and 3 through 8, although the instruments will remain functioning during theremaining gravity-sensing orbits. The mission will benefit from substantial levels of Earth-based support. Spectral ranges notcovered by remote-sensing instruments contain valuable information. JunoCam will not produce calibrated imaging, and so a
broad range of narrow-band and spectroscopic information at wavelengths of 0.3-2.0-µm would provide information on cloudproperties in the troposphere. Near-infrared high-resolution spectroscopy will supplement JIRAM by providing sensitivity tolines of minor constituents that serve as tracers of vertical winds. No Juno instrumentation will cover infrared wavelengths
greater than 5 µm (the mid-infrared), which provide direct information on temperature structure and the distribution of tracegases in both the troposphere and stratosphere, as well as cloud properties in the upper troposphere (pressures of 1 bar or less).
Another key element of support will be the need to supply the spatial context for remote sensing instruments that will have poleto-pole latitudinal coverage but only in strips that are 5 to 10 degrees in longitude. Equally important during this period will beobservations of changes in time, both to monitor the history and evolution of features that fall into the remote-sensing coverageof Juno as well as to determine velocity fields around features. Prior to solar conjunction in mid-2016, it will be important toassess the extent and lifetime of features that might be captured in the coverage of the atmosphere, e.g. the Great Red Spot, Oval
BA, brown barges or other cyclonic features, and blue-gray regions that are associated with clear and dry atmospheric conditions.
This assessment will inform the precise timing of the orbit-reduction maneuver in order to increase the probability of measuring
any of these features of interest around close passes with Jupiter. We are soliciting both professional and amateur observations,with the author serving as the point of contact for input. Support for this work was provided by the Juno Project through an award
from the National Aeronautics and Space Administration.
Keywords: Juno, Jupiter, imaging, spectroscopy, astronomy

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PPS01-17

Room:A03

Time:May 27 09:40-09:55

Solar UV/EUV response on Jovian thermosphere and radiation belt
KITA, Hajime1∗ ; MISAWA, Hiroaki1 ; TSUCHIYA, Fuminori1 ; TAO, Chihiro2 ; SAKANOI, Takeshi1 ;KASABA, Yasumasa1 ; MORIOKA, Akira1
1

Tohoku Univ., 2 Research Institute in Astrophysics and Planetology

In order to evaluate the solar UV/EUV heating effect on the Jovian radiation belt, we made coordinated observations for bothtemperature of the Jovian thermosphere using an infrared telescope and synchrotron radiation from the radiation belt (JSR) using
a radio interferometer.
Jupiter’s synchrotron radiation (JSR) is the emission from relativistic electrons in the strong magnetic field of the inner magnetosphere, and it is the most effective probe for remote sensing of Jupiter’s radiation belt from the Earth. Although JSR has beenthought to be stable for a long time, recent intensive observations for JSR reveal short term variations of JSR with the time scaleof days to weeks. It is theoretically expected that the short term variations are caused by the solar UV/EUV heating (hereafter
the B-M scenario): the solar UV/EUV heating for Jupiter’s upper atmosphere drives neutral wind perturbations and then the
induced dynamo electric field leads to enhancement of radial diffusion. If such a process occurs at Jupiter, brightness distributionof JSR is also expected to change. Previous studies have confirmed the existence of the short term variations in total flux density
and its variation corresponds to the solar UV/EUV variations. However, confirmation of the scenario is limited. The purpose ofthis study is to examine the B-M scenario based on radio interferometer and infrared observations, and reveal precise physicalprocesses of the inner magnetosphere.
We made simultaneous observations of the Giant Metrewave Radio Telescope (GMRT) and the NASA InfraRed Telescope
Facility (IRTF) in January 2014, in order to reveal whether the Jovian thermosphere responses to the solar UV/EUV and whether
this actually causes variations of the total radio density and brightness distribution of JSR. The total radio flux density, rotationaltemperature of H3 + , and solar EUV flux showed a similar decreasing trend until Jan. 10. These results support the B-M scenario.
On the other hand, the total flux density and the temperature increased after Jan. 12 even when the solar EUV flux decreasingalmost monotonically. The enhancement of the temperature and the total flux density after Jan. 12 might be caused by the highlatitude heating. A numerical simulation study of the Jovian upper atmosphere suggests that the high latitude Joule heating is
induced by solar EUV radiation and it affects the mid-low latitude thermosphere. It is shown that the high-latitude heating produces an atmospheric convection cell which propagates from the heat source region at both high and low latitudes. In addition
to that, if high latitude heating is caused by some processes other than the solar UV/EUV, it is expected that this also affects
the mid-low latitude temperature and the radiation belt: one of such effects might be brought by enhancement of field aligned
currents flowing into the high latitude region, which is driven by some global magnetospheric variations.
Thus, we found that the solar UV/EUV enhancement causes the variations in thermospheric temperature and intensity of JSR
had correlation from the combined simultaneous observations, which is consistent with the B-M scenario. It is also suggested
that one point should be taken into account in addition to the original B-M scenario, i.e., the high latitude heating effect on the
mid-low latitude thermosphere.
Keywords: Jovian radiation belt, Jovian thermosphere, Infrared spectroscopic observation, Radio interferometric observation,
Solar UV/EUV response

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PPS01-18

Room:A03

Time:May 27 09:55-10:10

Summary of Hisaki observation during one-year and the next
YOSHIKAWA, Ichiro1∗ ; EXCEED, Mission team2
1

University of Tokyo, 2 EXCEED Mission teamThe Sprint-A satellite with the EUV spectrometer (Extreme Ultraviolet Spectroscope for Exospheric Dynamics: EXCEED)
was launched in September 2013 by Epsilon rocket.
Now it is orbiting around the Earth (954.05 km x 1156.87 km orbit, the period is 104 minutes) and has performed a broad andvaried observation program for 1-year.
With an effective area of more than 1cm2 and well-calibrated sensitivity in space, the EUV spectrometer produces spectral
images (520-1480 A) of the atmospheres/magnetospheres of solar planets (Mercury, Venus, Mars, Jupiter, and Saturn) from theearth-orbit.
Continuous 3-month measurement for Io plasma torus and aurora of Jupiter was conducted with HST to witness the sporadic
and sudden brightening events occurring on one or both regions.
For Venus, Fourth Positive system of CO and some yet known emissions of the atmosphere were identified.
Mercury, Saturn,and Mars were also observed. Summary of 1-year observation will be presented.
Keywords: HIsaki, EUV, Planetary airglow, Solar planets

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PPS01-19

Room:A03

Time:May 27 10:10-10:25

Dynamics of Jupiter’s auroral acceleration investigated by multi-wavelength plasma remote sensing with space telescopes
KIMURA, Tomoki1∗ ; BADMAN, Sarah2 ; TAO, Chihiro3 ; YOSHIOKA, Kazuo1 ; MURAKAMI, Go1 ;YAMAZAKI, Atsushi1 ; TSUCHIYA, Fuminori4 ; BONFOND, Bertrand5 ; KRAFT, Ralph6 ; ELSNER, Ronald8 ;BRANDUARDI-RAYMONT, Graziella7 ; GLADSTONE, Randy9 ; FUJIMOTO, Masaki1 ; HISAKI, Science team1 ;HST, Cycle 20 go 13035 team1 ; CXO, Cycle 15 go 15100276 team1
1

RIKEN Nishina Center for Accelerator-Based Science, 2 Department of Physics, Lancaster University, UK, 3 Institut de Rechercheen Astrophysique et Planetologie, France, 4 Planetary Plasma and Atmospheric Research Center, Tohoku University, Japan,
5
Laboratoire de Physique Atmospherique et Planetaire, Universite de Liege, Belgium, 6 High Energy Astrophysics Division,
Harvard-Smithsonian Center for Astrophysics, US, 7 Mullard Space Science Laboratory, University College London, UK, 8 NASA
Marshall Space Flight Center, Space Science Office, US, 9 Department of Space Studies, Southwest Research Institute, Boulder,
Colorado, US
From January to April 2014, two observing campaigns by multi-wavelength remote sensing from X-ray to radio were performed to uncover energy transport process in Jupiter’s plasma environment using space telescopes and ground-based facilities.
These campaigns were triggered by the new Hisaki spacecraft launched in September 2013, which is an extremely ultraviolet(EUV) space telescope of JAXA designed for planetary observations.
In the first campaign in January, Hubble Space Telescope (HST) made imaging of far ultraviolet (FUV) aurora with a high special resolution (0.08 arcsec) through two weeks while Hisaki continuously monitored aurora and plasma torus emissions in EUV
wavelength with a high temporal resolution (more than 1 min). We discovered new magnetospheric activities from the campaign
data: e.g., internally-driven type auroral brightening associated with hot plasma injection, and plasma and electromagnetic filed
modulations in the inner magnetosphere externally driven by the solar wind modulation.
The second campaign in April was performed by Chandra X-ray Observatory (CXO), XMM newton, and Suzaku satellite
simultaneously with Hisaki. Relativistic auroral accelerations in the polar region and hot plasma in the inner magnetosphere
were captured by the X-ray space telescopes simultaneously with EUV monitoring of aurora and plasma torus. Auroral intensity
in EUV indicated a clear periodicity of 45 minutes whereas the periodicity was not evident in X-ray intensity although previous
observations by CXO indicated clear 40-minute periodicity in the polar cap X-ray aurora.
In this presentation, we show remarkable scientific results obtained these campaigns.

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PPS01-20

Room:A03

Time:May 27 10:25-10:40

Solar wind influence on Jupiter’s inner magnetosphere found by HISAKI/EXCEEDMURAKAMI, Go1∗ ; YOSHIOKA, Kazuo1 ; KIMURA, Tomoki1 ; YAMAZAKI, Atsushi1 ; TSUCHIYA, Fuminori2 ;KAGITANI, Masato2 ; TAO, Chihiro3 ; YOSHIKAWA, Ichiro4 ; FUJIMOTO, Masaki1
1

Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 2 Tohoku University, 3 Research Institute in
Astrophysics and Planetology, 4 The University of Tokyo
The dawn-dusk asymmetry of the Io plasma torus has been seen by several observations. One possible cause of this asymmetry
is a dawn-to-dusk electric field in Jupiter’s inner magnetosphere. However, the question what physical process can impose such
an electric field deep inside the strong magnetosphere still remains. The long-term monitoring of the Io plasma torus is a
key observation to answer this question. The extreme ultraviolet (EUV) spectrometer EXCEED onboard the HISAKI satellite
was launched in 2013 and observed the Io plasma torus for more than several months. We investigated the temporal variationof the dawn/dusk ratio of EUV brightness. Then we compared it to the solar wind dynamic pressure extrapolated from thatobserved around Earth by using magnetohydrodynamic (MHD) simulation. As a result we found clear responses of the dawndusk asymmetry to rapid increases of the solar wind dynamic pressure. This result agrees with the scenario that a dawn-to-dusk
electric field is imposed in the inner-magnetosphere by a field-aligned current.

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PPS01-21

Room:A03

Time:May 27 11:00-11:15

EUV observation for Jovian inner magnetosphere
YOSHIOKA, Kazuo1∗ ; MURAKAMI, Go2 ; KIMURA, Tomoki3 ; YAMAZAKI, Atsushi2 ; TSUCHIYA, Fuminori4 ;KAGITANI, Masato4 ; SAKANOI, Takeshi4 ; KASABA, Yasumasa5 ; YOSHIKAWA, Ichiro6 ; FUJIMOTO, Masaki7
1

Rikkyo University, 2 Institute of Space and Astronautical Science, 3 RIKEN Nishina Center for Accelerator-Based Science,
Planetary Plasma and Atmospheric Research Center, Tohoku University, 5 Department of Geophysics, Graduate School of Science, Tohoku University, 6 Graduate School of Frontier Sciences, The University of Tokyo, Department of Complexity Science
and, 7 Institute of Space and Astronautical Science/Earth-Life Science Institute, Tokyo Inst. of Tech.

4”HISAKI” the Japanese Earth orbiting satellite has been launched in September 2013 from the Uchinoura space center. The
EUV spectroscope ”EXCEED” on board the spacecraft is observing the planets in our solar system since the end of November
2013 [Yoshikawa et al. 2014]. The performance of the instrument (effective area, spectral and spatial resolutions, and etc.) aresame as been expected before the launch [Yoshioka et al. 2013]. Using the EUV spectra of the Jovian inner magnetosphere (Ioplasma torus) taken by the EXCEED, the plasma dynamics such as electron transportation or local heating process have been
revealed. In this presentation, we will show the whole results of Io plasma torus observation through the EXCEED, and we will
also explain the way of our approach for the Jovian plasma dynamics.
Keywords: EUV, Jupiter, magnetosphere

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PPS01-22

Room:A03

Time:May 27 11:15-11:30

Local electron heating around Io observed by the HISAKI satellite
TSUCHIYA, Fuminori1∗ ; KAGITANI, Masato1 ; YOSHIOKA, Kazuo3 ; NOZAWA, Hiromasa3 ; KIMURA, Tomoki2 ;MURAKAMI, Go3 ; YAMAZAKI, Atsushi3 ; KASABA, Yasumasa4 ; SAKANOI, Takeshi1 ; YOSHIKAWA, Ichiro5
1

Planetary Plasma and Atmospheric Research Center, Tohoku Univ., 2 ISAS/JAXA, 3 National Institute of Technology, Kagoshima
College, 4 Graduate school of Science, Tohoku University, 5 Department of Complexity Science and Engineering, Univ. of Tokyo
Io-correlated brightness change in Io plasma torus (IPT) has been discovered by the Voyager spacecraft and show an evidenceof local electron heating around Io. However, the observation data is still limited to investigate its detail properties and causeof the electron heating around Io is still open issue. EUV spectrograph onboard the HISAKI satellite carried out continuous
observation of IPT and Jovian aurora for 2.5 months since the end of Dec. 2013. It covers wavelength range from 55 to 145 nm,
a wide slit which had a field of view of 400 x 140 arc-second was chosen to measure radial distribution and time variation of IPT.
Observation of IPT with HISAKI found clear periodic variation in the IPT brightness associated with Io’s orbital period. The Iophase dependence shows that bright region is located just downstream of Io. The amplitude was larger in the short wavelengththan in long wavelength. These are evidence of local electron heating around/downstream of Io and consistent with the Voyager
result. In addition, it is found that the brightness also depends on the system-III longitude of Jupiter and has local maximum
around 120 and 300 degrees. Based on an empirical model of IPT, electron density at Io also shows maxima around the samelongitudes. This suggests that the electron heating process is related with IPT density at Io. Total radiated power from IPT on Jan.
2014 was 1.1 TW, which was about a half of the power measured by the Cassini UVIS instrument on Oct. 2000. Io-correlated
component has about 10 % of the total radiated power, showing that about 100 GW of power was converted to heat thermal
electron in IPT immediately after the generation of source energy around Io.
Keywords: Jovian magnetosphere

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PPS01-23

Room:A03

Time:May 27 11:30-11:45

Cassini/RPWS: A low frequency radio imager at Saturn
CECCONI, Baptiste1∗ ; LAMY, Laurent1 ; ZARKA, Philippe1
1

LESIA, Observatoire de Paris, France

The High Frequency Receiver (HFR) of the Radio and Plasma Waves Science experiment (RPWS) onboard Cassini is asensitive, and versatile radio instrument. Although the radio antenna connected to this instrument have no intrinsic directivity,
the HFR measurements can provide instantaneous direction of arrival, flux density and polarization degree of the observed radio
waves. Hence, the HFR can be described as an full-sky radio imager. As the instrument provides direction of arrival, radiosources can be located with some assumption on the propagation between the source and the observer. Hence, it is possible toproduce radio source maps and correlate them with observations at other wavelengths, such as UV or IR observations of theauroral regions of Saturn. The flux and polarization measurements together with the time-frequency shape of the radio emissions
can also be used to identify the radio emission processes.
We present a review of the results of the Cassini/RPWS/HFR observations since its arrival at Saturn in 2004: interpretationof the radio arc shapes and equatorial shadow zones; in-situ observations in the radio source region; comparison with otherwavelengths and particle measurements; confirmation of the Cyclotron Maser Instability (CMI) as the main emission mechanism
for auroral radio emissions; monitoring of the radio emission variability in time and location, etc. We will also show how the
future JUICE mission will benefit from these techniques.
Keywords: Radioastronomy, Saturn, Aurora, Magnetosphere, Cassini

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