PPS01-01

会場:A03

時間:5 月 26 日 12:00-12:15

木星型惑星を想定した雲対流の数値計算
Numerical Modeling of Moist Convection in Jovian Planets
杉山 耕一朗 1∗ ; 中島 健介 2 ; 小高 正嗣 2 ; 倉本 圭 2 ; 林 祥介 4
SUGIYAMA, Ko-ichiro1∗ ; NAKAJIMA, Kensuke2 ; ODAKA, Masatsugu2 ; KURAMOTO, Kiyoshi2 ;HAYASHI, Yoshi-yuki4
1
1

宇宙航空研究開発機構 宇宙科学研究所, 2 九州大学, 3 北海道大学, 4 神戸大学
ISAS/JAXA, 2 Kyushu University, 3 Hokkaido University, 4 Kobe University

木星・土星の大気では水などの凝結を伴う強い積乱雲が生成することが知られており, 天王星・海王星でも同様の対流雲の存在が理論的に推定される. 木星型惑星の雲対流は, 地球大気の場合と同様に, 大気の成層構造と物質分布の決定に重要な役割を担っていると考えられている. しかし, 厚い雲に覆われた巨大惑星の雲層を遠隔観測するのは困難であり, 巨大
惑星における雲対流と平均的大気構造との関係については未だ明らかとなっていない点が多い. この問題に対し我々は,複数成分の凝結および化学反応を考慮した雲対流モデルを開発し, 木星大気条件において, 雲の生成消滅が繰り返された
結果として決まる統計的平衡状態での大気構造を調べてきた (Sugiyama et al., 2009,2011, 2014). 本発表では, 土星と天王星を想定した同様の 2 次元数値計算を実行し, 雲対流と平均的大気構造との関係を議論する.
モデルは準圧縮系方程式 (Klemp and Wilhelmson, 1978) に基づく. 雲微物理過程は Nakajima et al. (2000) と同様に, 地
球で良く利用されている単純な雲微物理パラメタリゼーション (Kessler, 1969) を用いて定式化した. 放射過程は陽に計算
せず, 水平一様かつ時間変化しない熱強制で代用する. 土星・天王星では雲層における正味の放射加熱・冷却の鉛直プロ
ファイルが観測されていないため, 木星の観測結果に基づき 2 bar 高度から対流圏界面 (0.1 bar) の間を冷却することにした. 統計的平衡状態に至るまでの計算時間を短縮するため, 熱強制の値は木星大気における観測値より 2 桁大きい -1 k/dayとする. 計算領域は水平方向に 7680 km とする. 鉛直計算領域の大きさは, 土星条件で 480 km, 天王星条件で 650 km とする. 解像度は水平方向と鉛直方向共に 2 km とする. 下部境界での温度圧力は熱平衡計算 (Sugiyama et al., 2006) に基づいて決定した. 下部境界での凝結性成分気体の存在度は, 現実的ではないが, 研究の出発点として太陽組成と同じとする.
土星条件と天王星条件の計算結果の大きな特徴は, H2O 持ち上げ凝結高度に対応する湿潤対流層下部で強い上昇流が見られる一方で, 湿潤対流層上部に狭くて強い下降流が多数見られることである. 強い下降流が存在するという特徴は, 狭
くて強い上昇域と広くて弱い下降域によって特徴づけられた木星条件の計算結果と対照的である. 土星と天王星において下降流の大きさは上昇流と同程度の 50 m/s 以上であり, 湿潤対流層の上部では鉛直速度の歪度は負である. 天王星条件で得られた歪み度が最も小さく, このことは土星よりも天王星の方が下降流が卓越することを意味する. 土星条件と天王星条件において下降流が卓越するのは以下の 2 つの理由による. 1 つは対流運動が, 下からの加熱ではなく, 対流圏界面付近(0.1 <p <2 bar) での冷却によって駆動されるためである. もう 1 つの理由は, 対流圏上部の温度が木星大気よりも低温なことである. 土星と天王星では H2O の凝結がより下層 (高圧) で始まる. 湿潤対流層の上部では H2O 混合比がほぼゼロとなるため, その高度領域では H2O の凝結潜熱の寄与が非常に小さくなる.

キーワード: 木星大気, 湿潤対流, 数値計算, 雲解像モデル
Keywords: atmosphere of Jovian planets, moist convection, numerical modeling, cloud resolution model

1/1

PPS01-02

会場:A03

時間:5 月 26 日 12:15-12:30

The radiative cooling and the solar heating in Jovian troposphere
The radiative cooling and the solar heating in Jovian troposphere高橋 康人 1∗ ; はしもと じょーじ 3 ; 石渡 正樹 1 ; 高橋 芳幸 2 ; 杉山 耕一朗 4 ; 大西 将徳 2 ; 倉本 圭 1
TAKAHASHI, Yasuto1∗ ; HASHIMOTO, George3 ; ISHIWATARI, Masaki1 ; TAKAHASHI, Yoshiyuki O.2 ;SUGIYAMA, Ko-ichiro4 ; ONISHI, Masanori2 ; KURAMOTO, Kiyoshi111

北海道大学, 2 神戸大学, 3 岡山大学, 4 宇宙科学研究所
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

1/1

PPS01-03

会場:A03

時間:5 月 26 日 12:30-12:45

木星成層圏のシミュレーション研究：新しい放射コードの開発と力学への影響
Simulation study of Jupiter’s stratosphere: development of a new radiation code and impacts on the dynamics
黒田 剛史 1∗ ; Medvedev Alexander S.2 ; Sethunadh Jisesh2 ; Hartogh Paul2
KURODA, Takeshi1∗ ; MEDVEDEV, Alexander S.2 ; SETHUNADH, Jisesh2 ; HARTOGH, Paul21
1

東北大学大学院理学研究科 惑星プラズマ・大気研究センター, 2 マックスプランク太陽系研究所
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.
キーワード: 木星, 成層圏, 大気放射, 大気力学, 巨大ガス惑星, JUICE
Keywords: Jupiter, Stratosphere, Atmospheric radiation, Atmospheric dynamics, Gas giants, JUICE

1/1

PPS01-04

会場:A03

時間:5 月 26 日 14:15-14:35

Cassini-Huygens ミッションによる土星系探査結果ハイライト
Cassini-Huygens Mission Highlights: Discoveries in the Saturn System
Spilker Linda1∗ ; EDGINGTON Scott1 ; ALTOBELLI Nicolas2
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
1
Jet Propulsion Laboratory/California Institute of Technology, Pasadena, CA, USA, 2 ESA/ESAC, Villafranca del Castillo,
Madrid, Spain
Cassini-Huygens ミッションによる過去 11 年間に渡る土星系探査は，新しい発見と，さらなる未知の領域を拓いてきた。Cassini オービターは地球打ち上げ後の 7 年後，2004 年に土星周回軌道に入り，土星系最大の衛星 Titan に降下機を着陸させてその大気と地表の観測を行った。それ以来，Cassini による発見は土星，複雑な環構造，多様な衛星群，そして磁気圏の我々の理解を書き換え続けている。
Cassini にる数多くの発見の中でも，特筆すべきものは，比較的小さな衛星である Enceladus の南極域から噴出する氷
火山状のジェット，Titan の液体有機化合物の湖沼群と前生物的な化学組成を様相する大気から降る雨，土星北半球の巨大な嵐 (1990 年以来の規模) の高解像度・複数波長による画像観測，土星キロメートル波長放射と自転速度は一致しないという計測結果，Enceladus が土星の E 環粒子と磁気圏を満たす水分子の源であること，そして環系の三次元的な力学解
析の理解などがある。Cassini による土星系での発見は，惑星形成プロセスの全般的理解にも貢献している。
Cassini の過去 2 年間のみに焦点を当てても数多くの発見があった。注目すべき結果の幾つかをあげると，Titan の湖沼
群は両極域に分布し，そのうちいくつかの深さの計測に成功したことや、Enceladus 表面下の海の存在を明らかにしたこと，土星北極の巨大台風，Enceladus から噴きあがるジェット粒子の大きさは潮汐力に左右され，ジェット活動は遠土点付近で最大になること，Titan の湖・Ligeia Mare の深さは 150-200m であること，環の詳細構造には隕石衝突痕，propeller状構造の環の放射方向への伝播，そして土星内部振動などの影響が反映されること，Titan 表面下の海，太陽風と土星磁
気圏の強い相互作用が超新星爆発の衝撃波の理解を助けること，そして Titan の南極域の霞層は季節的なものだということなどがある。
Cassini プロジェクト終わりに向けた Solstice ミッションは，さらなる新発見を目指すものである。ミッションの最終フェーズである「Grand Finale」は 2017 年に開始され，近土点が D 環の内側に入り，極地方大気上層をかすめるような離心率と軌道傾斜角の高い軌道を 22 周回り，今までにない精度での重力場と磁気圏の測定を行い，環系と土星の質量の確定と，今までに探査機の入ったことのない領域での様々な In-Situ 計測を行う予定である。
このプレゼンテーションでは Cassini プロジェクトのここまでの 11 年間のハイライトと，この先 3 年間ミッション終了までの計画を説明する。

Cassini-Huygens は NASA,，European Space Agency (ESA)，そしてイタリア宇宙局 (Agenzia Spaziale Italiana, ASI) の共
同ミッションである。
このプレゼンテーションの内容の一部は California Institute of Technology の Jet Propulsion Lab で，NASA との契約によって行われ，アメリカ政府の予算に支えられています。R2015 California Institute of Technology

キーワード: Cassini, Saturn, Huygens, Rings, Titan
Keywords: Cassini, Saturn, Huygens, Rings, Titan

1/1

PPS01-05

会場:A03

時間:5 月 26 日 14:35-14:50

Cassini Imaging Science at Saturn: Global Atmospheric Dynamics and Cloud Morphology
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
SAYANAGI, Kunio1∗ ; INGERSOLL, Andrew P.2 ; DYUDINA, Ulyana A.2 ; EWALD, Shawn P.2 ;BLALOCK, John J.1
11

Hampton University, 2 California Institute of Technology
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.
キーワード: Planetary Science, Jovian Planet, Saturn, Cassini Mission, Atmosphere, International Cooperation
Keywords: Planetary Science, Jovian Planet, Saturn, Cassini Mission, Atmosphere, International Cooperation

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PPS01-06

会場:A03

時間:5 月 26 日 14:50-15:05

Exploration of Titan’s Seas
Exploration of Titan’s Seas
LORENZ, Ralph1∗
LORENZ, Ralph1∗
1
1

JHU Applied Physics Laboratory
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.

キーワード: Titan, Hydrocarbons, Oceanography, Exploration Vehicles, Radar
Keywords: Titan, Hydrocarbons, Oceanography, Exploration Vehicles, Radar

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PPS01-07

会場:A03

時間:5 月 26 日 15:05-15:25

JUICE: A EUROPEAN MISSION TO JUPITER AND ITS ICY MOONSJUICE: 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
BRANDT, 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
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.
キーワード: Jupiter, Ganymede, Europa, Callisto, Magnetosphere
Keywords: Jupiter, Ganymede, Europa, Callisto, Magnetosphere

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PPS01-08

会場:A03

時間:5 月 26 日 15:25-15:40

木星氷衛星探査計画 JUICE
Jupiter Icy Moons Explorer: JUICE斎藤 義文 1∗ ; 佐々木 晶 2 ; 藤本 正樹 1
SAITO, Yoshifumi1∗ ; SASAKI, Sho2 ; FUJIMOTO, Masaki1
1

宇宙研, 2 大阪大学大学院理学研究科宇宙地球科学専攻
Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 2 Department of Earth and Space Sciences,
School of Science, Osaka University

1

JUICE とは、ESA が 2012 年 5 月に選定したＬクラス計画であり、2022 年打ち上げ，2030 年木星系到着，2032 年ガニメデ周回軌道投入の予定である。木星到着後、まずは木星周回軌道から木星系の観測を実施し、ガニメデ周回軌道投入後はガニメデという太陽系最大の氷衛星の精査を行う。サイエンス・テーマは（１）巨大ガス惑星の世界の理解（２）氷衛星（ガニメデ，エウロパ，カリスト）の探査である。AO とその後の選定を経て決まった JUICE に搭載される 11 観
測機器提供チームのうち、３つの機器 (RPWI, GALA, PEP/JNA) については日本から JUICE-JAPAN がハードウェアの一部を提供する事になり、2 つの機器 (JANUS, J-MAG) についてハードウェアの提供は無いがサイエンス Co-I として参加することとなった。海外が主体となる極めて魅力的な大型計画へ日本から機器提供という形で参加することは今後とも活用されるべきである「海外計画への参加」という枠組みであり JUICE-JAPAN はその先駆けとなる。JUICE の科学的課題は (1) 系外惑星を意識した，巨大ガス惑星の世界の理解，および、(2) アストロバイオロジーを意識した，氷衛星（ガニメデ，エウロパ，カリスト）の探査である。木星周回軌道から木星系の観測（磁気圏，木星大気，エウロパ・
カリスト・ガニメデのフライバイ観測）を実施し、巨大ガス惑星の原型としての木星系探査を行うことで、「巨大ガス惑
星系の起源と進化」を解明する事、４つのガリレオ衛星のうち、エウロパ・カリストのフライバイ観測、太陽系最大の氷衛星ガニメデの周回観測による精査を実施し、生命居住可能領域の探査を行うことで、「生命存在可能領域としての氷
衛星地下海の形成条件」を解明することが JUICE の目的である。JUICE の打ち上げは、アリアン５で行われる。打ち上げ時ドライ重量は約 1800kg, 燃料は約 2900kg である（必要なΔ V は約 2700m/s）。3 軸制御の探査機であり、太陽電池
パドル面積は 70m2 、それにより約 700W の電力を発生させる。科学観測用には、重量 104kg、電力 150W というリソースが想定されている。通信は、X および Ka バンドによる。打ち上げ後は、地球・金星・地球・地球というスウイング
バイを経て、7.6 年かけて木星に到着する。ガニメデ周回軌道投入後は、ガニメデという太陽系最大の氷衛星の精査を目的とする（この精査に加えてエウロパとカリストのフライバイ観測があること、つまり、アストロバイオロジーの観点から注目を浴びる「地下海」を持つ氷衛星３つのすべてを JUICE は観測するということは、特筆に値する）。最終期には、高度 500km での周回観測を 100 日間、200km での周回観測を 30 日間実施し、最後はガニメデに衝突してミッショ
ン終了である。日本から JUICE-JAPAN として参加する、ハードウェア提供３機器 (RPWI, GALA, PEP/JNA) とサイエンス参加 2 機器 (JANUS, J-MAG) を足し合わせると、木星本体（JANUS）、木星磁気圏（PEP/JNA,RPWI,J-MAG）、氷衛星（GALA,J-MAG,JANUS）といった JUICE のサイエンス・テーマのすべてに、日本からバランス良く貢献が可能であることがわかる。2013 年 9 月に正式に JUICE-JAPAN WG が設立された後、JUICE-JAPAN WG は、平成 26 年 2 月に小規模プロジェクトの募集に対して応募し、9 月に理学委員会による MDR/SRR を通過した。その後 WG 活動として、欧州 PI との観測装置提供部分の確定作業、観測装置担当部分に関わる開発、宇宙研 SRR/所内経営審査に向けた準備等を実施。現在は、WG からプリプロジェクトへの移行時期である。今後、プリプロジェクト、プロジェクトと進み、平成
28 年度には PDR、平成 29 年度に CDR と進んでいく予定である。JUICE はプロジェクト終了までまだ約 20 年かかる長期間に渡るプロジェクトである。適宜世代交替を進めながら是非ともこの魅力ある大型ミッションへの参加を成功させたいと考えている。

キーワード: 木星, ガニメデ, 衛星探査
Keywords: Jupiter, Ganymede, Satellite Exploration

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PPS01-09

会場:A03

時間:5 月 26 日 15:40-15:55

ソーラー電力セイル実証機による外惑星領域探査： クルージング科学観測と木星トロヤ群その場計測
Outer Planet Exploration by the Solar Power Sail: Cruising Observation and In-situ Investigation of Jupiter Trojans
矢野 創 1∗ ; 松浦 周二 1 ; 中村 良介 2 ; 米徳 大輔 3 ; 癸生川 陽子 4 ; 青木 順 5 ; 森 治 1 ;ソーラー電力セイル WG1YANO, Hajime1∗ ; MATSUURA, Shuji1 ; NAKAMURA, Ryosuke2 ; YONETOKU, Daisuke3 ; KEBUKAWA, Yoko4 ;AOKI, Jun5 ; MORI, Osamu1 ; SOLAR POWER SAIL, Working group1
1

宇宙航空研究開発機構・宇宙科学研究所, 2 産業技術総合研究所, 3 金沢大学, 4 横浜国立大学, 5 大阪大学
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
1

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.
キーワード: ソーラー電力セイル, クルージング観測, 木星トロヤ群小惑星, 着陸探査, その場質量分析, サンプルリターン
Keywords: Solar Power Sail, Cruising Observation, Jupiter Trojan Asteroids, Surface Exploration, In-situ Mass Spectrometry,
Sample Return

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PPS01-10

会場:A03

時間:5 月 26 日 16:15-16:30

Tidal deformation of Ganymede and effects of a subsurface ocean: a model calculation in
preparation for JUICE
Tidal deformation of Ganymede and effects of a subsurface ocean: a model calculation in
preparation for JUICE鎌田 俊一 1∗ ; 木村 淳 2 ; 松本 晃治 3 ; Nimmo Francis4 ; 倉本 圭 1
KAMATA, Shunichi1∗ ; KIMURA, Jun2 ; MATSUMOTO, Koji3 ; NIMMO, Francis4 ; KURAMOTO, Kiyoshi1
1
1

北大, 2 東工大 ELSI, 3 国立天文台, 4 カリフォルニア大学サンタクルーズ校
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

会場:A03

時間:5 月 26 日 16:30-16:45

ガニメデの内部進化と地形形成：JUICE 計画での実証に向けてInterior evolution of Ganymede and its surface manifestation: toward JUICE measurements
木村 淳 1∗ ; 倉本 圭 2
KIMURA, Jun1∗ ; KURAMOTO, Kiyoshi2
1
1

東京工業大学地球生命研究所（ELSI）, 2 北海道大学
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

会場:A03

時間:5 月 26 日 16:45-17:00

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

Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
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.
キーワード: Europa, Icy Worlds, Astrobiology, Habitability, Outer Planets, Microfracturing
Keywords: Europa, Icy Worlds, Astrobiology, Habitability, Outer Planets, Microfracturing

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PPS01-13

会場:A03

時間:5 月 26 日 17:00-17:15

ハビタブルトリニティ概念のエウロパへの適用
Application of Habitable Trinity concept to Europa
丸山 茂徳 1∗MARUYAMA, Shigenori1∗
1
1

東京工業大学地球生命研究所
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

会場:A03

時間:5 月 26 日 17:15-17:30

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

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

キーワード: Europa, Jupiter, Torus, Magnetosphere
Keywords: Europa, Jupiter, Torus, Magnetosphere

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PPS01-15

会場:A03

時間:5 月 27 日 09:00-09:20

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

Institut de Physique du Globe de Paris (IPGP), 2 AIM (Astrophysique Instrumentation Modelisation)
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.
キーワード: Planet, Satellites, Formation
Keywords: Planet, Satellites, Formation

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PPS01-16

会場:A03

時間:5 月 27 日 09:20-09:40

JUNO による木星探査と地上からのサポート観測
The Juno Mission and the Role of Earth-Based Supporting Observations
Orton Glenn1∗
ORTON, Glenn1∗
1
1

Jet Propulsion Laboratory, California Institute of Technology
Jet Propulsion Laboratory, California Institute of Technology

NASA の JUNO 探査機は 2011 年に打ち上げられ，2013 年の地球フライバイによる増速を経て 2016 年 7 月に木星に到着する計画である。木星到着後は近木点が放射線帯の内側に入る離心率の高い楕円軌道に入り，木星を約 30 回周回する。JUNO ミッションの主な目的は木星大気深層の水分子の分布の計測，惑星近辺の重力場の解析，そして磁気圏環境の探査の 3 点である。これらの計測により木星内部の構造，組成，そして対流循環を三次元的に解析することが可能になる。また，それにより惑星表層の大気現象を木星の内部循環と結びつけて理解することも可能になる見込みである。これらの研究により，木星の形成と進化の過程を明らかにし，ガス惑星形成について総合的な理解を深めることも重要な目的である。
JUNO 探査機に搭載される観測機器は，電磁圏環境の in-situ 計測機器と，広範な周波数帯にわたって木星のリモート・センシング観測を行う機器の 2 つに分けられる。リモートセンシング機器が観測する波長帯は Ultraviolet Spectrometer(UVS) が 70-205 nm，Juno IR Auroral Mapper (JIRAM) が 2-5 μ m，そして Microwave Radiometer (MWR) が 1.3-50 cm となっている。それに加え，可視光カメラ JunoCam が RGB フィルターと 890 nm メタン吸収帯フィルターを用いてアウト
リーチ用画像を撮影する計画である。JUNO は木星を 30 回以上周回する予定であり，観測機器は連続的に運用されるが，リモートセンシング観測を優先して行うのは，最初の軌道と，軌道３〜８だけであるため（残りの軌道は重力場観測優先），表面構造の同時観測を行うためには地上からのサポートが不可欠であり，また，Juno 観測機器にカバーされない周
波数帯のスペクトル観測についても，地上からのサポートが重要になる。JunoCam は可視光画像を撮影するものの，撮像用 CCD は厳密な測光観測を行うのに十分な精度でキャリブレーション行うことができないため，対流圏雲構造の解析を行うには地上からの 0.3-2.0 μ m 波長でのワイドバンド・ナローバンド観測が必要になる。また，地上からの近赤外線
高スペクトル解像度観測により大気の微量成分の吸収線を測ることで，JIRAM データからは測定できない鉛直成分の風速の推定も可能になる。JUNO 探査機は波長>5 μ m の中赤外線帯を観測する機器を搭載していないため，この波長で地上から観測を行うことにより対流圏と成層圏の温度分布と大気微量成分および高度 1 bar 以上の雲構造の分析も必要である。
地上観測のもう一つの重要点は，JUNO のリモートセンシング観測データは木星のごく限られた地域のみをカバーする
ため，地上から取れる木星全球データなしには，リモートセンシングデータを時系列に当てはめて理解することができない点である。このためには，2016 年中期の木星の衝までに木星表面にある事象とそのタイムスケールを理解し，JUNO による観測に今から備える必要がある。地上からの観測により追跡観測が必要な大気事象の例として，大赤斑，Oval BA，Brown Barges，そしてその他の渦構造や，青灰色がかった大気凝結成分の密度が低いことが知られている地域がある。こ
れらの観測を地上から行うことにより，JUNO の軌道修正のタイミングや観測機器のポインティングなどについて，大気事象に合わせて能動的な運用する予定である。こういったサポートを行うため，JUNO チームはプロとアマチュアによる木星の国際共同観測を呼びかけている。
（JUNO プロジェクトとその研究活動は NASA からの助成を受けて行われています。
）

キーワード: Juno, Jupiter, imaging, spectroscopy, astronomy
Keywords: Juno, Jupiter, imaging, spectroscopy, astronomy

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PPS01-17

会場:A03

時間:5 月 27 日 09:40-09:55

木星熱圏・放射線帯の太陽紫外線応答について
Solar UV/EUV response on Jovian thermosphere and radiation belt
北 元 1∗ ; 三澤 浩昭 1 ; 土屋 史紀 1 ; 垰 千尋 2 ; 坂野井 健 1 ; 笠羽 康正 1 ; 森岡 昭 1
KITA, Hajime1∗ ; MISAWA, Hiroaki1 ; TSUCHIYA, Fuminori1 ; TAO, Chihiro2 ; SAKANOI, Takeshi1 ;KASABA, Yasumasa1 ; MORIOKA, Akira1
1
1

東北大学, 2 Institut de Recherche en Astrophysique et Planetologie
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.
キーワード: 木星放射線帯, 木星熱圏, 赤外分光観測, 電波干渉計観測, 太陽紫外線応答
Keywords: Jovian radiation belt, Jovian thermosphere, Infrared spectroscopic observation, Radio interferometric observation,
Solar UV/EUV response

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PPS01-18

会場:A03

時間:5 月 27 日 09:55-10:10

ひさき衛星の観測１年間のまとめ、今後
Summary of Hisaki observation during one-year and the next
吉川 一朗 1∗ ; EXCEED Mission team2
YOSHIKAWA, Ichiro1∗ ; EXCEED, Mission team2
1
1

東京大学, 2 EXCEED Mission team
University of Tokyo, 2 EXCEED Mission team

EUV 分光器（EXCEED) を搭載したスプリント衛星 A（ひさき）はイプシロンロケットで 2013 年 9 月に打ち上げられ、観測を開始しました。 現在も、地球の周回（954.05km × 1156.87km、周期１０４分）を飛翔しています。この 1 年の間に太陽系惑星の水星、金星、（地球）、火星、木星と土星を一通り、観測した。EUV 波長域に 1cm2 以上の有効面積を持ち、520-1480A の波長範囲でよく較正されています。
この測器を用いて、木星を約３ヶ月間にわたり連続的に観測した。
その結果、イオプラズマトーラスとオーロラの双方に起こる突発的な増光のイベントから高エネルギー粒子の内部磁気圏への流入を確認した。
また金星の観測からは、一酸化炭素の Fourth Positive バンドと窒素分子の輝線をはじめて同定することができた。水星、火星、土星も含め、1 年間の観察の概要を紹介します。
キーワード: ひさき, 極端紫外光, 惑星大気光, 太陽系惑星
Keywords: HIsaki, EUV, Planetary airglow, Solar planets

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PPS01-19

会場:A03

時間:5 月 27 日 10:10-10:25

宇宙望遠鏡群を用いた多波長プラズマ遠隔観測が明らかにする木星オーロラ加速のダイナミクスDynamics of Jupiter’s auroral acceleration investigated by multi-wavelength plasma remote sensing with space telescopes
木村 智樹 1∗ ; Badman Sarah2 ; 垰 千尋 3 ; 吉岡 和夫 1 ; 村上 豪 1 ; 山崎 敦 1 ; 土屋 史紀 4 ;Bonfond Bertrand5 ; Kraft Ralph6 ; Elsner Ronald8 ; Branduardi-Raymont Graziella7 ; Gladstone Randy9 ;藤本 正樹 1 ; ひさき サイエンスチーム 1 ; HST Cycle 20 GO 13035 team1 ; CXO Cycle 15 GO 15100276 team1
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（独）理化学研究所 仁科加速器研究センター, 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
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

会場:A03

時間:5 月 27 日 10:25-10:40

ひさき搭載 EXCEED が捉えた木星内部磁気圏における太陽風の影響
Solar wind influence on Jupiter’s inner magnetosphere found by HISAKI/EXCEED村上 豪 1∗ ; 吉岡 和夫 1 ; 木村 智樹 1 ; 山崎 敦 1 ; 土屋 史紀 2 ; 鍵谷 将人 2 ; 垰 千尋 3 ; 吉川 一朗 4 ;藤本 正樹 1
MURAKAMI, Go1∗ ; YOSHIOKA, Kazuo1 ; KIMURA, Tomoki1 ; YAMAZAKI, Atsushi1 ; TSUCHIYA, Fuminori2 ;KAGITANI, Masato2 ; TAO, Chihiro3 ; YOSHIKAWA, Ichiro4 ; FUJIMOTO, Masaki1
1

宇宙航空研究開発機構宇宙科学研究所, 2 東北大学, 3 Research Institute in Astrophysics and Planetology, 4 東京大学
Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 2 Tohoku University, 3 Research Institute in
Astrophysics and Planetology, 4 The University of Tokyo1

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

会場:A03

時間:5 月 27 日 11:00-11:15

木星内部磁気圏の極端紫外光観測
EUV observation for Jovian inner magnetosphere吉岡 和夫 1∗ ; 村上 豪 2 ; 木村 智樹 3 ; 山崎 敦 2 ; 土屋 史紀 4 ; 鍵谷 将人 4 ; 坂野井 健 4 ; 笠羽 康正 5 ;吉川 一朗 6 ; 藤本 正樹 7
YOSHIOKA, Kazuo1∗ ; MURAKAMI, Go2 ; KIMURA, Tomoki3 ; YAMAZAKI, Atsushi2 ; TSUCHIYA, Fuminori4 ;KAGITANI, Masato4 ; SAKANOI, Takeshi4 ; KASABA, Yasumasa5 ; YOSHIKAWA, Ichiro6 ; FUJIMOTO, Masaki7
1

立教大学, 2 宇宙科学研究所, 3（独）理化学研究所 仁科加速器研究センター, 4 東北大学 惑星プラズマ・大気研究セン
ター, 5 東北大学大学院 理学研究科 地球物理学専攻, 6 東京大学大学院 新領域創成科学研究科 複雑理工学専攻, 7 宇宙科学研究所／東京工業大学地球生命研究所
1
Rikkyo University, 2 Institute of Space and Astronautical Science, 3 RIKEN Nishina Center for Accelerator-Based Science,4
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.

”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.
キーワード: 極端紫外光, 木星, 磁気圏
Keywords: EUV, Jupiter, magnetosphere

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PPS01-22

会場:A03

時間:5 月 27 日 11:15-11:30

衛星イオ−プラズマトーラス相互作用による電子加熱
Local electron heating around Io observed by the HISAKI satellite
土屋 史紀 1∗ ; 鍵谷 将人 1 ; 吉岡 和夫 3 ; 野澤 宏大 3 ; 木村 智樹 2 ; 村上 豪 3 ; 山崎 敦 3 ; 笠羽 康正 4 ;坂野井 健 1 ; 吉川 一朗 5
TSUCHIYA, Fuminori1∗ ; KAGITANI, Masato1 ; YOSHIOKA, Kazuo3 ; NOZAWA, Hiromasa3 ; KIMURA, Tomoki2 ;MURAKAMI, Go3 ; YAMAZAKI, Atsushi3 ; KASABA, Yasumasa4 ; SAKANOI, Takeshi1 ; YOSHIKAWA, Ichiro51

東北大学惑星プラズマ・大気研究センター, 2 宇宙科学研究所, 3 鹿児島高専, 4 東北大学大学院理学研究科, 5 東京大学新領域複雑理工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.
キーワード: 木星磁気圏
Keywords: Jovian magnetosphere

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PPS01-23

会場:A03

時間:5 月 27 日 11:30-11:45

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

LESIA, Observatoire de Paris, France
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.
キーワード: Radioastronomy, Saturn, Aurora, Magnetosphere, Cassini
Keywords: Radioastronomy, Saturn, Aurora, Magnetosphere, Cassini

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