JAXA SOLAR-C mission
JAXA SOLAR-C Working Group
Saku Tsuneta (WG chair)
AGU/SPD May 30 20081

Solar physics from space in Japan
Yohkoh (1991- 2001)
With NASA/PPARC

Hinotori(1981-1982)
Hinode (2006-) with NASA/STFC/ESASOLAR-CJ-FY2016(provisional)

AGU/SPD May 30 20082

Two SOLAR-C mission concepts
under study• Plan A: Out-of-ecliptic magnetic/X-ray and helioseismic
observations of the polar and the equatorial regions toinvestigate properties of the polar region, meridional flow
and magnetic structure inside the Sun to the base of theconvection zone.
• Plan B：High spatial resolution, high throughput, highcadence spectroscopic (polarimetric) and X-ray
observations seamlessly from photosphere to corona toinvestigate magnetism of the Sun and its role in heatingand dynamism of solar atmosphere.
• Launch Date: Japanese fiscal year 2016 (provisional)– Expects joint observations with highly complementary missions– NASA SDO (whole sun field of view)– ESA&NASA Solar Orbiter (Insitu and stereo obs with SOLAR-C)– NASA Solar probe (In-situ)
AGU/SPD May 30 20083

Plan-A: Exploration of polar region,internal structure and solar dynamo
The Sun as a star
• Scientific objective– Measure meridional flow at high latitudes, and see where it turns
downwards– Detect magneto-sound speed anomaly located in the tachocline
region (flux tube/sheet imaging in tachocline)– Observe the vector magnetic fields of photosphere andchromosphere and coronal imaging in X-ray/EUV– Obtain acoustic speed and angular rotation speed distribution in
the polar region– Understand acceleration mechanism of fast solar wind
– Monitor total irradiance (optional)– Study influence of the Sun to heliosphere• Model payload– Photospheric and chromospheric dopplergram– Stokes-polarimeter for photosphere and chromosphere– X-ray/EUV imager– Optional: total irradiance monitor, in-site instruments, andcoronagraph
AGU/SPD May 30 2008

4

Plan-A: A new possibility
Imaging of flux tubes in tachocline
A high-inclination orbit and dual observations•Observe Doppler velocity at high latitudes without undesired projection•Observe waves penetrating deep into the sun with dual stations.
By choosing launch timing,use precious 7 degree tiltof solar axis

Skip angle versus travel-time perturbation
due to flux sheet at tachocline

SOLAR-C

100kG corresponds to25msec travel timedifference.

Courtesy T. Sekii
0deg

50deg

100deg150degRequired inclination : 40～50 minus 7 degree= 33～43
AGU/SPD
May degree:
30 2008 Optimum angle to reach 5bottom of CZ

Plan A Orbit and Engine Trade-off
Case 1:

Ion engine + Earth swing-by

Case 2:Ion engine + Earth swing-by + Venus swing-by

Case 3:Chemical engine + Jupiter swing-by

Case 4:

Chemical engine + Jupiter swing-by + Earth swing-by<Trade-off items>
flight time until starting observation, achievable inclination,observational timing, payload mass, thermal design,tele-communication link, etc.
ex.) One possible solution of Case 1 assumes,
Observe both polar and equatorial- JAXA H2A launch
Regions maintaining ～1AU distance- Initial mass = 1200kg.
- Payload mass = 100kg.
Achieves Inclination (to the Solar equator) of30 deg. in 2 years from the launch,
45 deg. in 5 years from the launch.

Plan-B brings new discovery space thoughenhanced spectroscopic capability seamlessly
covering entire atmosphere
Hinode discoveries
Waves in prominence
Chromospherictransition region
jets due toreconnection
Waves alongspicules

Slow solar wind

Polar kG fields
Supersonic downflow
Convective collapse

Penumbral
micro-jets
Magnetic velocity
Fluctuation
Local dynamo
process

Ubiquitous
Horizontal
fields
AGU/SPDMay 30 2008

High coronalturbulence

77

Rutten, R., ASP-CS, 184, 181, 1999

Chromosphere more dynamic
than expected!

AGU/SPD May 30 2008

82006 Dec 17 20:00-21:00 UT CaII H broad band filter images taken with Hinode/SOT

Hinode and SOLAR-C Plan-B•

Hinode/SOLAR-C– Demonstrates power of spectro-polarimetry from space• Significantly enhance spectro-polarimetric capabilities to UV and near-IR– Dynamism of chromosphere is a major Hinode discovery. Chromospheric
dynamics may generate disturbance to corona: new implication to coronalheating (Isobe et al 2008)• High time resolution, high throughput spectrometer– Little diagnostic capability for chromosphere and transition regions• Seamless observations from photosphere to corona•

Scientific Objective– Obtain precise chromospheric and, if possible, coronal vector magnetic
field maps in addition to photospheric magnetic maps with high spatial andtemporal resolution– Obtain coronal 3-D magnetic field map from chromospheric vector field,
predict location and evolution of neutral-sheets, dicontinuities for transientand stationary coronal heating and eruption– Reveal causal relationship of photosphere-chromosphere-transition regioncorona to understand coronal/chromospheric heating and dynamism– Understand the nature of hidden magnetism: Is the observed B tip of theiceberg?
– Deepen Hinode discoveries with quantitative analysis: waves, turbulence,magnetic reconnection
AGU/SPD May 30 2008
9– Study influence of the Sunto heliospherePlan B model payload•

General
– From imaging to spectroscopy• Concentrate best possible lines to represent each layer of atmosphere– High resolution, high S/N, and high time resolution• High throughput multi-object-spectrograph or equivalent needed– From visible to visible+UV+near IR• Seamless coverage of photosphere, chromosphere, TR and corona•

Model payload– Near IR-Visible-UV telescope （TBD-1.1 micron）• ＞50cm diffraction-limited telescope （0.1-0.4arcsec）– Ultra-high resolution EUV/X-ray telescope– High resolution high throughput coronal spectroscopic capability•

Key point1 : Chromospheric, and if possible coronal spectropolarimetry for vector magnetic field observations– Needs He10830 or equivalent with Zeeman+Hanle sensitivity– Evaluate potentiality of UV and EUV lines for Hanle-effect diagnostics ofchromosphere and corona– Closer to force-free layer: provide better BC for coronal field extrapolation:
concern on the adequacy on photospheric BC•

Key point 2: High spatial and temporal resolution chromosphericand transition region spectroscopyfordynamics
AGU/SPD May 30
200810Development of SOLAR-C concept• JAXA SOLAR-C WG refines both plans, compare
science, technology, and other constraints, and prioritize
the two plans with international partners.
• International SOLAR-C science definition meeting– week of November 10 2008 at JAXA/ISAS-JSPEC• Purpose of meeting– Refine science cases for plans A and B– Determine option for Plan-A orbit and engine for further study– Propose model science instruments and identify key technology
issues– Discuss consistency and synergy with NASA and ESA plans– Form international sub working groups for specific critical issues– Establish connection with space weather
AGU/SPD May 30 200811

SOLAR－C development schedule(provisional)• FY2016• FY2015• FY2011～14• FY2010• FY2008～9• FY2007

LaunchS/C tests
Flight and proto model
Phase-A
Concept study
JAXA SOLAR-C WG(FY: Japan fiscal year starting April 1.)

AGU/SPD May 30 2008

12Summary• Solar physics community in Japan has so far
developed 3 solar missions over past 25 years.
• We recognize that success of Hinode andYohkoh is due to strong international support.
• Solar physics community and related-disciplines
in Japan strongly desire and endorse one of theSOLAR-C mission concept to be realized in mid2010s.
• The JAXA SOLAR-C working group invites USand European participation to the SOLAR-C
program, following our remarkable history ofcollaboration.
AGU/SPD May 30 200813