SOLAR-C PLAN-B: Mission Concept

Y. Katsukawa and SOLAR-C WG
SOLAR-C SDM
2008.11.18-21

Outline
1. Beyond HINODE••

Highlights of HINODE discoveries
Beyond HINODE

2. SOLAR-C Plan B mission concept••

Mission instruments
System requirements

3. Key items addressed in the meeting2008.11.18-21

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SOLAR-C Plan B• Pursues high resolutional observations with enhanced
spectroscopic capability from photosphere to corona toinvestigate magnetism of the Sun and its role in heatingand dynamics of the solar atmosphere.

• Advantages of SOLAR-C– Enhanced spectroscopic (+polarimetric) capability• Use the solar atmosphere as laboratory plasma by thepowerful diagnostic capability– High time resolution, high throughput spectrometer• Catch elemental processes of the solar plasma such as
waves and reconnection– Complete coverage of the solar atmosphere throughphotosphere, chromosphere, TR, and corona
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Magnetic field dynamics in the photosphere

Vertical fields
Lites et al.
Ishikawa et al. Centeno et al.

•Katsukawa et al.
Ichimoto et al.
Horizontal fields

QS photospheric magnetic fields– Formation of flux tubes, ubiquitous horizontal
fields•Sunspot structures– Penumbral filaments and Evershed flow
– Umbral dots, light bridges, MMFs etc.
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Waves/oscillations in chromosphers/coronae
Okamoto et al.

De Pontieu et al.

• Oscillations/waves areobserved everywhere in thesolar atmosphere, which may
be important in energy transfer
to heat the atmosphere.
– Period: 2 - 5mins or longer– Oscillation amplitude: ~1000km– Velocity amplitude: 10 – 20 km/s
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Mariska et al.
5Chromospheric/X-ray jets driven bymagnetic reconnection
Shibata et al.

Katsukawa et al.
Cirtain et al.

•Plasma ejections are ubiquitously observed in the wide range ofspatial/temporal scales, which are probably driven by magneticreconnection.
– Spicules, penumbral microjets, chromospheric jets, explosive events, X-rayjets, etc.
– Duration:<1min ~ minutes ~ 1 hour
– Spatial scale: <1000km ~ 5,000km ~ 50,000km

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Wedemeyer-Bohm (2008)2008.11.18-21

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Coronal flows, solar wind, and non-therm vel.
Sakao et al.

Harra et al.

•Outward flow along magnetic fieldlines in the corona.
– Velocity ~ 100km/s– Source of slow solar wind•

Non-thermal broadening near thefootpoints of coronal loops– Signature of nanoflares?
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Hara et al.
Doschek et al.

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8AR evolution, flare onset

Kubo et al.

Schrijver et al.

•Continuous observations of vector fields
in the photosphere together withobservations of the corona has
provided unprecedented information
about flare onset.
– NLFFF extrapolation from vector fields
in the photosphere to the corona

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SOLAR-C SDM9• Elemental MHD processes started to appear by highresolutional observations.
• We are still in the middle of studies using HINODE andother existing instruments. We are sure that we are on apath toward solving major problems in solar physics.
– Chromosphere and corona heating– Flares/CMEs onset• It is also true that we are not satisfied with the current
instruments. We have to think about what we should donext, beyond HINODE.
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10Beyond HINODE• Spectroscopic capability of chromospheric and TR lines– HINODE/SOT has a capability to observe only photospheric linesof Fe I. Only imaging observations of chromospheres are available.
– HINODE/EIS observes mainly coronal plasma > 106K.
– There is a gap between the photospheres and the coronae, whichmake it difficult to understand energy transfer and dissipation
between them.

• Extend the observing wavelength range to fill
the gap between the photosphere and thecorona.
• Capability of spectroscopic(+polarimetric)
observations in both photospheric andchromospheric lines to enable quantitative
diagnostics
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Beyond HINODE (cont'd)• Temporal cadence in spectroscopic observations– It takes very long time (longer than 1 hour) to get spectral
observations over a wide area.
– We have to reduce FOV if we like to achieve the high temporalcadence. This prevents us from studying dynamical phenomenaby spectroscopic observations.

• High throughput telescope to increase thetemporal cadence in spectroscopic
observations (for EUV obs)
• Instruments to use photons efficiently inspectroscopy (for Vis/NIR obs)
– Multi-slit or multi-object spectroscopy– Narrow-band filter imager with rapid wavelengthscanning2008.11.18-21

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Beyond HINODE (cont'd)• Spatial resolution to resolve elemental physicalprocesses– Is 0.2"-0.3" resolution enough to resolve magnetic field andconvection dynamics in the photosphere, waves and magnetic
reconnection occurring in the chromosphere?
– It is not easy to connect fine scale structures (<1") seen in thephotosphere/chromosphere to coronal structures because oflack of spatial resolution (>1") in coronal observations.

• Increase the spatial resolution in coronalobservations.
• We have to discuss how critical improving
spatial resolution is in observations ofphotosphere and chromosphere.
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SOLAR-C Plan B• Pursues high resolutional observations with enhanced
spectroscopic capability from photosphere to corona toinvestigate magnetism of the Sun and its role in heating
and dynamics of the solar atmosphere.

• Advantages of SOLAR-C– Demonstrates power of spectro-polarimetry• Use the solar atmosphere as laboratory plasma by thepowerful diagnostic capability– High time resolution, high throughput spectrometer• Catch elemental processes of the solar plasma such aswaves and reconnection– Complete coverage of the solar atmosphere,
photosphere, chromosphere, TR, and corona
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Strawman Mission Instruments• NIR-Visible-UV telescope– >50cmφ diffraction-limited telescope (0.1- 0.4arcsec resolution)with advanced imaging and spectroscopic instruments– Wide wavelength coverage with capabilities of observing
spectral lines useful for diagnosing the solar atmosphere fromphotosphere to transition region• EUV spectroscopic telescope– Wide wavelength coverage to see solar atmosphere fromtransition region to corona.
– High spatial resolution (better than 0.5")– High throughput to achieve high cadence.

• Ultra-high resolution EUV/X-Ray imaging telescope– Imaging of emission from coronal plasma.
– High spatial resolution (better than 0.5")
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NIR-Vis-UV telescope•

Extend the observing
wavelength range to UV
and NIR in order to seethe upper
chromospheres/TR.

SOLAR-B/SOTSOLAR-C
Lyα
CIV

MgII

CaII

HeI

•

The mirror coating ischanged to Al+MgF2 from
Ag for UV observations.

•High throughput by >50cm φ allows us to perform high resolutional
spectroscopic observation•Eff. area 30-200 cm2 in 120-300nm (ref. 0.01 ~ 0.3 cm2 for SUMER)
100- 400 cm2 in > 400 nm (ref. 100 ~ 200 cm2 for HINODE/SOT)
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16Transition region

106K

Photosphere

Chromosphere

CoronaCIV

Temperature

Lyα
He I 10830A
Mg II h/k105K

HINODE/BFICa II H/KCa II 8500A
Hα

EUV/X-Ray telescope

Mg I bSOLAR-CNa I D1/D2104K

Fe I

HINODE/NFINIR-Vis-UV telescope
HINODE/SP100
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Candidates of spectrum lines• Chromospheric and transition region dynamics– Lyα 1216A– CIV 1550A– Other chromospheric and transition region lines at <2000A– Mg II h/k 2800A– Ca II H/K 3900A• Chromospheric vector magnetic fields– He I 10830A– Ca II 8500A IR triplet– MgIb 5172A• Photospheric vector magnetic fields– FeI 5247A/5250A etc.

• Photospheric/lower chromospheric imaging– CN band (3883A)– Vis/UV continuum
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Optical performance in UV•

50cmφ diffraction-limited telescopeachieved by HINODE SOT– STR ~ 0.8 @ 500nm(diffraction limit: 0.25")
STR ~ 0.5 @ 300nm(diffraction limit: 0.15" )– We can achieve at least the same
spatial resolution 0.2" in VUV as
HINODE SOT in Vis.

HINODE Optical Telescope Assembly (OTA)••

Micro-roughness– Minimum requirement 1nmRMS isalready achieved by OTA.

Key technical items– Contamination control for UV observations (preliminary study isreported by Dr. Urayama)– Higher heat absorption by the Al mirror coating– Image stabilization for UV obs

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Characteristics of NIR-Vis-UV telescope• Throughput and spatial resolution (50cmφ aperture)
S/N ~ 50~200 in Lyα and MgII h/k(0.1"pixel (0.2"res), 1sec exp, λ/∆λ = 2x104)
S/N ~ 20~50 in CIV and other VUV lines(0.1"pixel (0.2"res), 10sec exp, λ/∆λ = 2x104)
S/N ~ 2x103 in FeI 5250A(0.1"pixel (0.2"res), 1sec exp, λ/∆λ = 1x105)
S/N ~ 104 in CaII 8500A and He10830A(0.2"pixel (0.4"res), 6 sec exp, λ/∆λ = 1x105)
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NIR-Vis-UV telescope
Focal plane instruments (very preliminary)(1)

Aperture

Wavelength

Focal plane instruments>50 cm(VUV-Vis-NIR)

120nm<λ<1µm(1)(2)

utilizing UV/Vis
dichroic mirror(2)

UV package•
UV spectrometer•
UV Imager
Vis/NIR package•
Multi-spectral line spectro-polarimeter•
Narrow-band imager

30 ~ 50 cm(VUVtelescope)

120nm<λ<200nm
(TBD)

(1)

UV package•
UV spectrometer•
UV imager>50 cm(NUV-Vis-NIR)

280nm<λ<1µm(TBD)(1)

Vis/NIR package•
Multi-spectral line spectro-polarimeter•
Narrow-band imager

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UV package•

UV Spectrometer– Spatial resolution: better than 0.2"/pixel– Spectral resolution: λ/∆λ> 4x104 (~ 50mÅ @ 2000A)– Spectrum lines, possible candidates•

Lyα, Si II, Si IV, CIV, Mg II h/k etc.

– (Optional) Polarimeter for Zeema/Hanle diagnostics•

UV Imager– Slit jaw camera to know the slit location– Spatial resolution: better than 0.1"/pixel– Observing wavelengths••

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UV continuum for the low chromosphere
Imaging of bright lines (Lyα, CIV, MgII h/k) if a narrow-band
filter (~1A pass-band) is available
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NIR-Vis package•

Multi-spectral line spectro-polarimeter––––

At least two spectral lines can be observed simultaneously orby switching pre-filters.
Spatial resolution: ~ 0.1"/pixel
Spectral resolution: ~20mA/pixel
Candidates of spectrum lines••••He I 10830A (Chromospheric magnetic fields)
Ca II 8500A (Chromospheric magnetic fields)
Fe I 5250A (Photospheric magnetic fields)

Narrow-band imager––––Spatial resolution: better than 0.1"/pixel
Spectral resolution: 20 ~ 100mA
Rapid wavelength scan by Fabry-Perot or Lyot filter
Broadband interference filter for continuum imaging

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EUV spectroscopic telescope• Key performances required– High sensitivity, time cadence better than 10 sec even in QS– Spatial resolution better than 0.5”
– Wide temperature coverage from TR to corona, mainly in widecoverage of transition region (some 10, 000 – a few MK)• To realize high sensitivity telescope, the number of
optical elements (filters, mirrors) should be minimized.
– One optics candidate is off-axis parabola mirror (>20cmφ) andTVLS grating, and vis. light-blind dector.

Ref: Talks by J. Davila and G. Doschek
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SOLAR-C
EUV/X-Ray telescope

Wilhelm et al. (1995)
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Ultra-high resolution EUV/X-Ray imaging telescope• Key performances required– Spatial resolution should be better than 0.5"
– Good throughput to get an image with a reasonable exposureduration• Normal incidence Cassegrain optics with an large
effective area, with multi-layer coating sensitive to EUV
emission lines emitting from coronal plasma.
OR• Grazing incidence optics with an large effective area tocover emissions from coronal plasma with varioustemperatures. Spectroscopic capability by photon
counting detector as an option.

Ref: Talks by L. Golub/E. Deluca, and T. Sakao
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Spacecraft system concept• Utilize high-precision space technologies acquired
during the HINODE development, and minimize
new developing items for realizing SOLAR-C.
– Hinode SOT heritage : 50cm diffraction-limited
telescope and image stabilization system– Spacecraft design, including S/C attitude control, microvibration control technique• Launch vehicle: JAXA H-IIA– ~3t for the Sun-synchronous orbit (SSO)– ~2t for the Geostationary orbit (GEO)

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New items for SOLAR-C• Ultra-high date rate
– High temporal cadence spectroscopic observations
require very much telemetry. One to two orders ofmagnitude larger than HINODE.
– Orbit (SSO or GEO), on-board data processing, anddata donwlink are critical in the mission.

• Operate SOLAR-C like a ground-based telescope– It's provide a great advantage if we can move the slit
on an interesting target with looking at real images.

The details are to be given by T. Shimizu.
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Key items addressed in the meeting• Which problems are solved or unsolved ?
– Convection, photospheric magnetic field dynamics,
local dynamo– Sunspot structure, penumbra, magneto convection– Chromospheric and coronal heating, solar wind
acceleration– Prominences, Flare/CME initiation mechanism

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Key items addressed in the meeting• What kind of information is missing inunderstanding the unsolved problems?
– Direct measurements of magnetic fields inchromospheres and coronae ?
– Spatial resolution better than 0.2" to see very small
scale waves and reconnection ?
– High temporal resolution to catch very high frequency
waves and dynamics?
– Spectroscopic and polarimetric accuracy to measure
weak magnetic fields and dynamics?
– Wide FOV to get global magnetic field configuration?

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Key items addressed in the meeting• How do we meet the scientific requirements inSOLAR-C?
– Spectrum lines most suitable for diagnostics ofchromospheres, TR, and coronae– What kind of observing instruments are suitable for
NIR-Vis-UV telescope. Is 50cmφ enough?
– How to build the high resolutional + high throughput Xray/EUV telescope

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