La Magnétosphère De Jupiter Avant JUNO P. Zarka

Home , Gravity Science (Juno), UVS (Juno)

La magnétosphère de Jupiter avant JUNO

P. Zarka LESIA & USN

NASA’s 2nd New Frontiers mission https://www.missionjuno.swri.edu/

PI: Scott Bolton (SwRI) • ~60 Co-Is, ~10% Fr. • Solar-powered, spinning spacecraft • 8 Science instruments • Launched 5 August 2011 • 5-year cruise to Jupiter • Arrives at Jupiter 4 July 2016 Juno Science Objecves

Origin Determine O/H rao (water abundance) and constrain core mass to decide among alternave theories of origin.

Interior Understand Jupiter's interior structure and dynamical properes by mapping its gravitaonal and magnec ﬁelds

Atmosphere Map variaons in atmospheric composion, temperature, cloud opacity and dynamics to depths greater than 100 bars at all latudes.

Magnetosphere Characterize and explore the three-dimensional structure of Jupiter's polar magnetosphere and auroras. Juno - Spacecra & Payload SPACECRAFT DIMENSIONS Diameter: 20 meters JunoCam Height: 4.5 meters camera UVS UV spectrometer Waves Radio & plasma JIRAM JEDI IR spectrometer High-energy particles JADE Gravity Science Low-energy particles Magnetometer

MWR Microwaves Juno Payload

Gravity Science (X and Ka Band) — GRAV (JPL/ASI, Folkner)

Microwave Radiometers (6) — MWR (JPL, Janssen)

Magnetometer — MAG (GSFC/DTU, Connerney)

Energec Parcle Detectors (3) — JEDI (APL, Mauk)

Jovian Auroral Distribuons Exp. (4 → 3) — JADE (SwRI, McComas)

Waves — (U of Iowa, Kurth)

UV Spectrometer — UVS (SwRI, Gladstone)

IR Camera/Spectro — JIRAM (ASI, Adriani)

+ Camera — JunoCam (Malin, Hansen) Juno Mission Plan

Baseline mission: 32 polar orbits

Perijove ~5000 km

14 day period Polar Magnetosphere Exploraon

Locaon is Key: Juno passes directly through auroral ﬁeld lines.

A suite of instruments is used to understand the physics: JADE, JEDI, MAG, Waves, JIRAM, UVS Juno Orbit In Magnetic Coordinates

15 15 Perijove 3 Perijove 3Perijove 17 Perijove 17Perijove 31 Perijove 31 Perijove 2016 DOY 315 16:46 Perijove 2016PerijovDOY 31e520116:746DOY 103 07:28 Perijove 2017PerijovDOY 10e320107:728DOY 256 21:49 Perijove 2017 DOY 256 21:49 10 10

5 5 315 315

103 103 ) ) J J (R (R 0 0 z z

-5 -5 256 256

-10 -10

5 10 15 20 25 305 105 1510 2015 2520 3025 305 105 1510 1520 2520 3025 305 10 15 20 25 30 ρ(R ) ρ(R ) ρ(R ) ρ(R ) ρ(R ) ρ(R ) J J J J J J Early orbit Late orbit Auroral field lines crossings

PJ5 Science Acvity Period PJ 50 North starts DOY 334 = 11/29/2016 15:52 As Seen From Above North Pole

Juno Orbit #5 50 10 Pj 5 2016 335 15:51:60 70

5 270 90 334 335

0 ]

J VIT4 VIP4 VIPAL Khurana −5 180 336

Z magnetic [R PJ 50 South As Seen From Above North Pole −10 −50

337 −70 −15

270 90

−20 0 5 10 15 20 25 30 Rho [R ]

VIT4 VIP4 VIPAL Khurana 180 Key measurement « Perfect » magnetic ﬁeld model post JUNO → reliable context for magnetospheric studies Key measurement « Perfect » magnetic ﬁeld model post JUNO → reliable context for magnetospheric studies Open questions (After Bagenal et al., Space Sci. Rev., 2014 + update STM 2016/03) http://lasp.colorado.edu/home/mop/resources/hosted-meetings/junostm16/workshop-on-jupiters-aurora/

STRUCTURE • Is the kink of the oval a longitude or Local Time effect ? Why is the north auroral ≠ from the south ? • Is there a polar cap with open ﬁeld lines ? Of what size ? Variability ? • Where do the dark regions and various auroras map ? • How do the polar regions relate to the long magnetotail observed by Voyager 2 and New Horizons ? Open questions DYNAMICS • What is the role of the solar wind ? How is the magnetosphere coupled to it ? How deep does its inﬂuence penetrate the magnetosphere ? How does it (+shocks) modulate the main oval + radio emissions ? Relatively to internal dynamics ? • Over what timescales does Io volcanic activity affect magnetosphere? Io’s Sodium Nebula Open questions

DYNAMICS • How much mass and momentum are transferred through the magnetopause ? Is there reconnection (at high-latitude?) vs small-scale Kelvin-Helmholtz Instability ? • What is the origin of quasi-periodic ﬂares ? Ionosphere modulated ? in phase ? How can distant regions communicate ? • Are there Planetary Period Oscillations at Jupiter ? Observable ? Are Saturn’s PPO comparable to system IV ? UV brightness

Where KH instabilities are probable

Where magnetic reconnection is probable β=10 >16MeV electrons β=1 Open questions AURORA • How are the x-ray/UV/Vis/IR/radio emissions related ? • What is the source of the various auroras ? Why is there (transient) UV emission everywhere at high latitudes ? How can there be emission on ﬁeld lines that should connect to the sw (don’t quite see this at other planets) ? • Do auroras reveal the energy and mass transfer in Jupiter’s magnetosphere ? • What is the relationship with local injections (importance, scale size) ?

Auroral Patch Open questions AURORA • What is the source of the various auroras ? Why is there (transient) UV emission everywhere at high latitudes ? How can there be emission on ﬁeld lines that should connect to the sw (don’t quite see this at other planets) ? • Where does the downward current region(s) lie(s) ? • How does f-a current density relate to auroral intensity ?

Downward Current?

Upward Current Alfven Aurora Alfven Aurora

Upward Current Downward Current Alfven Aurora Jupiter’s Main Oval: Upward Current Region

(1)Parallel electric fields (double layers). (2)Perpendicular electrostatic shocks. (3)Accelerated electrons. (4)Anti-Earthward ion beam. (5)Strong wave activity. (6)Deep density cavity. Upward Current Region: Electric Fields & electron energies

FAST ORBIT 1858 FAST ORBIT 1858 500 500 250 250 0

(mV/m) -250 0 -500 (mV/m) 1000 -250 500 -500 0 -500 1000 (mV/m) -1000 -1500 500

) -3 10 0 -500 5 (mV/m) -1000 5 to 50 V/m

Density (cm 0 -1500 4 9

10 ) 103 -3 10 500 km, 10 s

2 -s-sr-eV 10 2 Log eV/

1 cm Electrons (eV) 10 6 5 7 104 103 Density (cm Electric 0 field amplitudes should be considerably

2 -s-sr-eV 10 2 Log eV/ Ions (eV)

1 cm larger4 and, depending on boundary layer 9 10 4 10 101 -4 thickness, much faster time scale.

/Hz 3 2 10 100

2 -s-sr-eV 10 2 Log eV/ Freq. (kHz) -1

10 -12 Log (V/m)

Electrons1 should have higher energies. cm

UT :06:35 :06:40 :06:45 :06:50 :06:55 :07:00 Electrons (eV) 10 6 ALT 3953.1 3950.3 3947.4 3944.5 3941.6 3938.6 ILAT 70.8 71.0 71.1 71.2 71.3 71.4 MLT 21.2 21.2 21.2 21.2 21.2 21.2 4 7 Minutes from 1997-02-09/06:06:35 10 103

2 -s-sr-eV 10 2 Log eV/ Ions (eV)

1 cm 10 4 101 -4 /Hz 2 100

Freq. (kHz) -1

10 -12 Log (V/m) UT :06:35 :06:40 :06:45 :06:50 :06:55 :07:00 ALT 3953.1 3950.3 3947.4 3944.5 3941.6 3938.6 ILAT 70.8 71.0 71.1 71.2 71.3 71.4 MLT 21.2 21.2 21.2 21.2 21.2 21.2 Minutes from 1997-02-09/06:06:35 Alfven Aurora

Ionospheric resonator at Jupiter ~20 Hz (Earth is <1 Hz) ⇒ Jovian S-bursts ? Downward Current Region: Where is it ? What to look for ?

(1) Anti-Jovian accelerated electrons: field-aligned and broader energy. (2) Strong wave activity (3) Parallel electric fields (double layers). (4) Perpendicular electrostatic shocks (diverging). (5) Ion conics. Open questions ACCELERATION • X-ray aurora is unique on Jupiter, how/why ? Are there MeV potential drops ? • Is there energetic particle precipitation of 100s of keV (Are atmospheric models reliable) ? Why are the precipitating electrons so energetic ? How does the auroral acceleration process work at Jupiter ? Are they completely different from Earth ? • Heating vs acceleration for producing energetic plasma ? • What is the altitude/vertical structure of the acceleration region above aurora ? Satellite footprints ? • What mechanisms accelerate particles to radiation belt energies (injections, w-p, etc.)?

X-ray emissions Open questions

RADIO / WAVES • Where and how are auroral radio components generated ? • Is the Cyclotron Maser oblique mode dominant (why) ?

Resonance condition : Growth rate : Oblique/ Loss-cone Open questions RADIO / WAVES • Will in-situ JUNO measurements permit us to address Cyclotron Maser microphysics in unexplored regimes (100s keV) ?

4 (%)

ce fcutoff

)/f 2 ce

(f-f 0

-2 fCMI -4 A B C 08:12 08:24 08:36 08:48 09:00 09:12 Day 2008-291 (h:m) Open questions

RADIO / WAVES • Are there Double-Layers, Electron/Ion holes in auroral regions? • How are they related to Up/Down/Alfvén regions ? How interleaved ? • Role of plasma waves in the auroral acceleration region ?

T ~ 1.5 eV

~ 200 s ? T ~ 0.14 eV

0 0 Open questions SATELLITES • How different are acceleration processes in the Io spots and in the wake ? • Does Ganymede interact with Jupiter’s B ﬁeld via reconnection of Alfvén waves ? • Is there heavy mass loading from Europa (e.g. via atmospheric escape)? UV wake? Radio emission?

Ganymede footprint

Europa footprint Comparisons with Cassini

(16 sept. 2017) JUNO’s Earth-based Supporng Observaons

+ • HST UV, IRTF H3 , Giant Telescopes: COMICS, VISIR, CanariCam (Mid-IR) • Professionals, Amateurs → Glenn Orton coordinator

• HISAKI / EXCEED, small JAXA EUV spectrometer in Earth orbit (Kimura et al.)

• Radio Decameter : Nançay Decameter Array (France), LOFAR (various European locaons), UTR-2, URAN 1-4 (Ukraine), LWA (USA), Tohoku U., Fukui Inst. Tech., U. Elect. & Comm., Kochi U. (Japan), Radio Jove = “Juno Ground Radio” → Bapste Cecconi, coordinator → VO / VESPA, MASER web site @ Meudon

• JUNO dedicated receiver at Nançay Decameter Array

• Synchrotron observaons (LOFAR) : Daniel Santos-Costa, Julien Girard et al. (coll. ONERA)

Data

• JUNO data will be put into the PDS within 6 months → public !