1. Jupiter’s 2-D Magnetosphere- Ionosphere-Thermosphere coupling model Chihiro Tao 1,2, Michel Blanc 1 1. IRAP, Univ. de Toulouse/UPS-OMP/CNRS 2. now at NICT (chihiro.tao@nict.go.jp) Journée scientifique Juno/JUICE, IRAP, Toulouse, 13-14 October 2015 Session 3 : Ionosphère et thermosphère aurorales

2. Jupiter Environment solar wind magnetosphere Io plasma torus magneti c equator magnetic field ・ Largest planet in the solar system, fast rotation （ 9h55m ： rotation energy is x200,000 Earth’s ） ・ Strong magnetic field （ momentum x20,000 Earth’s ） ・ Plasma source at Io locating inner mag. ◆ Rotation-driven system (cf. Earth ： SW-driven) ex. Plasma rotates in vast region, periodic phenomena ◆ High energy particle accelerator, Pulsar-like Fig. Jovian magnetosphere altitude above 1 bar [km] 0 500 1000 1500 ~1000 K10 5-6 /cc ionosphere thermosphere neutral temperature electron (equator) (aurora region) homopause ~300 km 2000 Fig. Jovian ionosphere/thermosphere several 100 km ・ Gas-planet ： H 2, He, H, CH 4, C 2 H 6, … ・ Ionosphere/thermosphere interact with magnetosphere Io plasma torus http://www.lowell.edu/users/spencer/ 1. Introduction

3. Magnetosphere-Ionosphere Coupling 1. Introduction Fig. Jupiter’s aurora [Grodent et al., 2003] Main oval Io footprint Ganimede/Europa footprint Polar emission Plasma from Io is transported outward  Lag from corotation  Discrepancy causes convection E-field  Current curcuit J x B (@ equator) accelerates magnetospheric plasma toward corotation =Transport momentum from planet Jupiter’s main oval is considered to be a part of this current Jupiter neutral wind magnetospheric plasma field-aligned current Fig. Multi-regional coupling Io J B momentum transfer fast rotation ω, corotation E [Hill, 1979], Energy transfer estimation [Hill et al., 1983], Neutral slippage [Huang and Hill, 1989], FAC in the system [Hill, 2001; Cowley and Bunce, 2001, 2003], Σp feedback [Nichols and Cowley, 2004], Energy transfer [Cowley et al., 2005], Φp feedback [Nichols and Cowley, 2005; Ray et al., 2009; 2010, 2012], Thermosphere contributions [Tao et al., 2009; Smith and Aylward, 2009], solar wind response [Cowley and Bunce, 2003ab; Cowley et al., 2008; Yates et al., 2012, 2014], solar EUV variation [Tao et al., 2010; 2014], LT due to magnetosphere [Ray et al., 2014], and Saturn applications.

4. Ionosphere-Thermosphere Region 1. Introduction Observation: ion velocity ~1 km/s is observed by Doppler shift of the H 3 + infrared (IR) line [e.g., Rego et al., 1999; Stallard et al., 2001; 2003]. From H 2 IR line, neutral velocity < 1.0 km/s [Chaufray et al., 2011]. H 3 + IR [Sakanoi et al. in prep.] [Stallard et al., 2003] Fig. Neutral wind [Achilleos et al., 2001]. neutral~ several 100s m/s Model: ion velocity ~1 km/s, neutral ~100s m/s [e.g., Achilleos et al., 1998; Bougher et al., 2005]. Joule/auroral heating >> solar EUV

5. Jupiter’s Coupling System 1. Introduction Ionospheric plasma Neutral Magnetospheric plasma Io Fig. Schematics for Jovian MIT coupling ◆ How thermospheric wind and current distribute under interaction? Plasma in the Jovian magnetosphere rotates in vast region with production at innermost Io and outward transport of magnetospheric plasma ⇒ Angular momentum transfer from the planet through coupling Angular Momentum Thermosphere/Ionosphere region ( Joule/auroral heating >> solar EUV) ⇒ Dynamics affected a lot by the coupling Heating, Ionization

6. (Our) Model Overview 2. Model (i) Thermosphere/Ionosphere 2D (3 components in latitude & altitude) (ii) Magnetospheric plasma 1D (azimuthal component in radial) Assumption: ・ Rotation axisymmetric ・ Ignoring the Alfven transit time ・ Magnetic field dipole on ionosphere empirical model at magnetospheric equator [Nichols and Cowley, 2004] Static condition Jupiter Neutral wind Magnetospheric plasma Field-aligned current (FAC) Fig. Model Region ⇒ calculate (i) thermosphere/Ionosphere model and (ii) torque equation of the out-flowing magnetospheric plasma, interactively

7. Model: Thermosphere 2. Model ― Primitive Equations ― Boundary Condition ・ mirror @equator, pole ( ∵ To include the effect from another hemisphere) ・ flux constant @ upper ・ corotation (v=0) fixed temperature @lower Fig. Model Region: Thermosphere Hydrodynamic Equilibrium Momentum Equations Energy Equation Mass Conservation State Equation ― Calculate… neutral atmospheric dynamics (v) & energetics (T) auroral electron H2H2 ・・・・・・ equator pole 90 deg. lat. 0 deg. ・・・・・・ Δ=0.5 deg. 250 km altitude ~2000 km Δ=0.4 scale height 30 levels Joule heating ion drag ionization/heating molecular/eddy viscosity & conduction H3+H3+ IR cooling ionization/ heating CxHy+CxHy+ wave heating

8. Model: Ionosphere 2. Model H2+H2+ H3+H3+ CH 5 + CH 4 + C2H3+C2H3+ C2H5+C2H5+ C2H2+C2H2+ C3Hn+C3Hn+ C4Hn+C4Hn+ CH 4 H2H2 C2H2C2H2 H2H2 H2H2 hν, electron hν C2H2C2H2 C2H2C2H2 C2H2C2H2 C2H2C2H2 CH 4 C2H4C2H4 H2H2 Fig. Ion chemistry Ionization by solar EUV [Richards et al., 1994] auroral electron precipitation [Hiraki and Tao, 2008] →Ionospheric Ion chemistry →Pedersen conductance Σ + recombination Fig. Profiles of ionization rate from Monte Carlo calculated (dot) & parameterized (solid) results [Hiraki and Tao, 2008] Electron energy spectrum varies as a function of FAC in order to satisfy Knight relation as Nichols and Cowley [2004]

9. Model: Magnetosphere & Coupling 2. Model Quasi-Static Condition: after ~200 rotation Based on previous M-I coupling models [e.g., Nichols and Cowley, 2004]

10. Coupling Current & Thermosphere 3. Results FAC is formed ⇔ Obs. 0.04-0.4 μA/m 2 [Gustin et al., 2004] meridional temperature & wind max(Vy)=77 m/s max(Vz)=0.98 m/s Fig. Latitudinal distribution of FAC (left) and meridional temperature and wind fields (right). Ionosphere→ Magnetosphere (auroral ele. prec.) Magnetosphere →Ionosphere Temperature: Joule heating in high latitudes Meridional circulation : heating in the high latitudes

11. Wind Fields 3. Results Anti-corotational direction Neutral wind : max 742 m/s ∵ Ion drag, Coriolis force Ion wind : max 2.1 km/s ⇔ Observation ~(0-3) km/s Neutral zonal wind Ion zonal wind Mag.Equator Plasma Fig. Zonal velocities of neutral wind (left) and ion wind (right) and magnetospheric plasma angular velocity normalized by the planetary one (down). ←Without coupling

12. Powers in the System 3. Results Power Magnetospheric acce. Ion drag Joule heating ↑torque by J x B Transferred to the magnetosphere: Joule heating in the atmosphere: Total power extracted from planetary rotation by this current system: Fig. Latitudinal profile of power per unit area. 7.9x10 11 6.4x10 13, 3.2x10 13, 7.9x10 11 W Total over hemisphere cf. estimated from obs.: 10 12 ‐ 10 14 W Reflecting magnetospheric plasma velocity profile and neutral wind. Ion drag in the atmosphere: <73.5 ﾟ ： P M is dominant >74 ﾟ ： P J is dominant [e.g., Cowley et al., 2005]

13. Neutral Wind Effect on the Coupling Ionospheric Pedersen Current Fig. Latitude-altitude map of k (upper) and σ k (lower) and FAC lat. profile (center). k: reduction of electric field by Vn compared to the case of rigid corotation “ Neutral-ion coupling” [Millward et al., 2005] σk : contribution on current around the FAC peak latitude * 30% reduction of electric field * 90% is attributed by <550 km altitude σ k 90% 4. Discussion

14. Variation of the System ② solar wind ① solar EUV -These variations are indicator to know the system -MIT modeling approaches: * Response to solar EUV variation [Tao et al., 2014] * Response to solar wind variation [Yates et al., 2014] 5.9 R J 2 R J 50- 100 R J radiation belt Io ~30 R J increase plasma corotation lag magnetopause 5. Application Io plasma variation LT (local time) variation

15. ① Solar EUV Variation 5. Application Variation of synchrotron emission from the Jovian radiation belt over a few days is associated with solar EUV variation[Miyoshi et al., 1999; Bhardwaj et al., 2009; Tsuchiya et al., 2010, 2011; Kita et al., 2013] How? [Brice and McDonough, 1973] The thermospheric response to the solar EUV flux  thermosphere wind  disturbance in the ionospheric electric field & corotation electric field  The field modulates radial transfer of the energetic particle cf. thermosphere has less effect by EUV heating. How much? [after Kita et al., 2013] [Tsuchiya et al., 2011] Solar EUV Jupiter’s synchrotron flux density Solar EUV Jupiter’s synchrotron flux density

16. ① EUV Variation 5. Application ΔT Δ|V| Δlog10(σP) 0 rot. 5 10 15 20 25 30 40 45 latitude altitude time time [rot] F10.7 160 80 0 10 20 EUV setting [Miyoshi et al., 1999] Investigation : Response of MIT model on solar EUV variation Results MIT coupling system shows twice variations, direct and high-to-low latitude propagation. [Tao et al., 2014] ○ Synchrotron flux density EUV

17. ① Solar EUV Variation 5. Application □ EUV enhancement increases angular momentum transfer The increase power ~ 10 13 [W] is larger than EUV input energy ~10 12 [W] cf. EUV power is 1.6×10 12, 3.0×10 12, and 4.5×10 12 W for F10.7 = 80, 160, and 240, respectively  Positive feedback of the system works through the ionospheric conductance □ Model estimated velocity variation is less than that required from the radiation belt model (from 95m/s to 150m/s [Miyoshi et al., 1999], from 302m/s to 339m/s [Tsuchiya et al., 2011])  Ambiguities in EUV model, 3D effect, other ambiguity in MIT and/or radiation models…? [Tao et al., 2014]

18. ② Solar Wind Variation 5. Application Initial  compression  expansion [Yates et al., 2014] 5.9 R J over 3-hour mag. pause at 45 ⇔ 85 R J Io ~30 R J plasma corotation lag magnetopause Method: Change the magnetopause and magnetospheric plasma angular velocity over 3 hours (steady  compression  expansion) Results: Variation of temperature (-45 ~ 175 K), velocity, current (several factors), and powers (2x10 15 W). Enhanced temperature and velocity propagation toward both high and low latitudes. Auroral enhancement with 1 degree poleward shift are consistent with observation [Nichols et al., 2009]

19. Summary We have developed a new numerical model calculating axisymmetric thermosphere dynamics and torque equation of the out-flowing magnetospheric plasma. 1. Thermosphere dynamics and field-aligned current interact with each other. 2. The rotation power extracted in the coupling system is used mainly for magnetospheric plasma acceleration in the region below 73.5 ﾟ latitude, while it is dissipated mainly as Joule heating in the higher latitudes. 3. Neutral dynamics mainly in <500 km altitudes reduces coupling electric field by ~30%. 4. Solar EUV variations would cause larger energy transfers in the system than input, due to a positive feedback of the system through the ionospheric conductance 5. Solar wind dynamic pressure variations would provide non-linear response and transient wind and temperature variations in the coupled system.

20. Toward Juno observations Jupiter Neutral wind Magnetospheric plasma Field-aligned current Fig. Model Region Step-1: Relate model parameters with observable parameters Field-aligned current ⇔ UV Ionosphere H 3 + density + temperature ⇔ IR Step-2: Constrain parameters by observation and comparison magnetic field + UV  field-aligned current particle obs.  auroral electron spectrum, mag. plasma velocity (?) IR obs.  temperature IR high-spectral obs. (ground-based)  wind field *Link these observed parameters in a model to evaluate energy transfer in the system *Constrain how much “additional” heating is required. Or other ideas/suggestions ?