1. HISAKI mission – ひさき – Chihiro Tao 1,2, Nicolas Andre 1, Hisaki/EXCEED team 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 1 : Les missions spatiales et leur support sol.

2. Introduction: Hisaki/EXCEED “Hisaki” is a space telescope satellite by JAXA EXCEED (=Extreme Ultraviolet Spectroscope for Exospheric Dynamics) instrument is onboard Hisaki. Targets of Extreme-ultraviolet (EUV) imaging spectrometer (1) Atmospheric escape from Venus, Mars, and Mercury (2) Surrounding plasma and aurora emissions from Jupiter and Saturn Launch ： September 14, 2013 http://www.jaxa.jp/projects/sat/sprint_a/

3. Introduction: Hisaki/EXCEED orbiting around the Earth -weight 348 kg -perigee 950 km, apogee 1150 km -inclination 31 degree -period ~106 min. -observe Jupiter, Venus, Mars, Mercury, …  Continuous observation for ~50min. per each 106 min. over several months  It is planned to observe until Spring 2017 ←Thick lines show observation period [Yoshikawa et al., 2014 SSRev] Possible targets: *close to the equatorial plane *sun-observer-target angle >40 deg.

4. Introduction: Hisaki/EXCEED Light camera Main mirror EUV spectroscopy slit http://www.jaxa.jp/p ress/2013/11/20131 126_hisaki_j.html EXCEED (1) (2) (3) [Yoshioka et al., 2013] There are three-slit modes. (1) 10’’ and (3) dumbbell are used for Jupiter

5. Jupiter obs. using the 10” slit  Geocorona high-spectral resolution (~3A)  Plasma parameters [Yoshioka et al., 2014] Observed spectra & Best-fit model spectra dawn

6. Jupiter obs. using the 10” slit [Yoshioka et al., 2014] Plasma parameters: Electron column density, temperature, hot (>10 keV) electron components, S+, S++, and S+++ fractions Increasing hot fraction with radial distance suggests the fast and continuous resupply of hot electrons responsible for exciting the whistler- mode waves

7. Jupiter obs. using the dumbbell slit northern pole Jupiter Io’s orbit Io plasma torus aurora emission Io plasma torus This provides aurora and torus observation simultaneously. Auroral spectra is comparable with HST observation with different wavelength coverage.

8. Jupiter obs. using the dumbbell slit Hisaki obs. aurora CH 4 less abs. aurora CH 4 abs. CR EXCEED Auroral electron energy power over 700-1800A ele. flux [#/sec] ele.flux density [#/sec/m 2 ] before accel. j //0 (@2.5 keV) solar wind dynamic pressure [nPa] from model HST/STIS obs. January 2, 2014 Derived aurora and electron parameters Both wavelength (CH 4 abs. and non-abs.) increases.  Number flux variation [Tao et al., JGR accepted]

9. Summary Hisaki/EXCEED provides good monitoring of Jupiter aurora and Io plasma torus activities continuously. * Io plasma torus: spatial and spectral information * Jupiter northern aurora: spectral information Hisaki/EXCEED will observe Jupiter from early 2016, which would be complementary information with Juno and Hubble Space Telescope etc. observations.

11. expects for Juno In-situ (Juno) and remote (Juno) conjugates auroral particle, acceleration, and emission What are similar and what are different from Earth? Simultaneous multi-wavelength obs. (Juno) auroral particle precipitation in UV & atmosphere in IR Global/dayside (Hisaki, HST, IR-ground, …) & close-up/nightside (Juno) comparisons different temporal/spatial scales + LT coverage: How aurorae enhance/vary? Solar wind (Juno) and aurora (Juno, Hisaki, HST, IR-ground) comparison Direct solar wind monitoring provides more reliable (incl. magnetic field) information to establish the response.  Magnetospheric source exploration by JUICE How/where auroral electrons are driven? How the magnetosphere varies? solar wind

12. We refer to the color ratio (CR): the ratio of the intensity of a waveband unabsorbed by hydrocarbons to that of an absorbed one,  auroral electron energy [e.g., Livengood and Moos, 1990, Gerard et al., 2003, 2014; Gustin et al., 2004]. Since Hisaki wavelength coverage cannot provide CR STIS, we defined a new CR EXCEED. Parameter estimation 1 CR STIS [Gérard et al., 2014 ] CR EXCEED

13. Parameter estimation 2 CR EXCEED  energy ( ⇔ potential drop φ // ) number flux ( ⇔ j // ) I (1385–1448 A)  total power  energy flux E f acceleration theory magnetospheric parameter N 0, k B T 0 ★ Acceleration theory: Linear-approximated Knight relation [Knight, 1973]: under the parallel potential drop φ // is much larger than source electron energy k B T 0 and is much less than the mirror ratio. electron density and temperature from obs. j // / e φ // ~ j //0 /k B T 0 = eN 0 (k B T 0 /2πm e ) 1/2 / k B T 0 ∝ N 0 /T 0 1/2 ★ Auroral region (1250 km width at VIP4 L=30) is assumed to obtain spatially- integrated value to flux per unit (e.g., j // )

14. Aurora Area Estimation Over 700-1800 A * “1250 km width at VIP4 L=30” was evaluated by comparison with HST image.