UV/EUV Spectroscopic
Observations
by
G. A. Doschek
Space Science Division, NRL
Solar-C Science Definition
Meeting
19 November 2008

The Solar Atmosphere: Outstanding Problems•

The connectivity of the atmosphere from the photosphere into
the corona is unclear– Current instrumentation cannot spatially resolve the UV/EUV
chromosphere/transition region– There is a mismatch in present spatial resolution from thephotosphere into the corona– Plasma diagnostics are averages over too large spatial andtemporal scales•

Testing models of the solar atmosphere requires data that do
not exist– Physical parameters as a function of spatial position in coronal
flux tubes and the connectivity of the flux tubes with thephotosphere and magnetic field are inadequately known– The time evolution of coronal flux tubes is currently only poorly
known.

•

CONCLUSION: If the above observational problems are notovercome, we will not be able to test adequately our models of
the energetics and dynamics of the solar atmosphere. Plan B
addresses these problems. Achieving seamless (same very
high spatial/spectral/temporal resolution with co-alignment)from the photosphere all the way into the corona is much morethan an incremental increase in capabilities.

Some Specific Noteworthy Plan
B Coronal Science Objectives• The origin of the solar wind
• The nature of coronal loops– What are they?
– What heats them?
– How do they evolve?

• Solar flares– Testing the “Standard Model”– Understanding the physics in the reconnection
region• Flux emergence and CME initiation

Spectroscopically Exploring the Solar Atmosphere in
Temperature Space••

Visible to ~1900 Å: Dominated by the continuum, mostly absorption
lines
1700 – 1100 Å: The photosphere, chromosphere, lower transition
region. A few coronal lines for above the limb (no coronal disk
observations)– UV allowed and intersystem lines of ions, e.g., C I – C IV, N IV, N V, O I – O
V, Si IV, S IV
– Forbidden and intersystem lines of coronal ions, e.g., Si VIII, Fe X, Fe XI,
and Fe XII; flare forbidden line of Fe XXI– Temperatures from 1 x 104 K to about 2.5 x 105 K•

1100 Å – 500 Å: the lower and upper transition region but limited
coronal access for disk observations, some forbidden lines for flares,
e.g., Fe XVII, Fe XVIII, Fe XIX, Fe XXII– UV/EUV allowed lines of ions such as O II – O VI, H I, He I, He II– Temperatures from 2.5 x 105 K up to about 1 x 106 K•

500 Å – 170 A: the corona and flares (some transition region lines)– Coronal allowed lines of many ions (e.g., Fe IX – Fe XVII, Ca XIV – Ca XVII),
flare lines of Fe XXII, Fe XXIII, Fe XXIV
– Temperatures from about 8 x 105 K up to about 20 x 106 K•

Below 170 Å : flare allowed lines of Fe XVIII through Fe XXIII between
about 90 Å and 140 Å.

The Structure of the Solar Transition Region

The classical transition region

Classical temperature structure
What best describes thesolar transition region –e.g., the classicaltransition region, coolloops, or separatrix
surfaces? Transition
region structures arearound 100 km is size,
below most current EUV
instrument resolution.

The cool loop/funnel model

The Sun at 320,000 K(2 x 105 km2, SUMER)

Model of Sub-Resolution
Filamentary Structure ofTransition Region
Spicules at 105 K

Solar spectra show
from filling factorsthat the transition
region contains finestructures withdimensions ranging
from small values ofabout 1” (700 km)
down to very smallvalues of about
0.043” (30 km).

Opacity arguments
indicate path lengthsof about 100 km (O III
line from SUMER.

Note A. Vourlidas Ly-alpha talkActive Region
H I Ly-ε 937 Å
10,000 K
Structures appear thesame at different
temperatures – structures
are unresolved.

Active Region
S VI 933 Å
200,000 K
Plan B allows a new physics
regime of the chromosphereto be explored.

Active Region Outflows

SOHO/EIT: “Fe XII”

Hinode/EIS: Fe XII 195.12 ǺActive Region
11 Dec. 2007
Fe XII 195.12 Å
00:24:16 UT-178”, -144”
60s exposures
FOV: 256”x256”
SOT magnetogramfrom Doschek et al. 2008, ApJ, 686, 1362

Correlation of Doppler Outflow Velocities
Non-thermal motions

The correlation implies
unresolved flows

Photospheric Properties of Outflow Regions
Fe XII FWHM

SOT Ca H image

SOT G band image

SOT magnetogramModeling Contributions of Active Regions
To the Heliospheric Magnetic Field

Potential field source surface
coronal model

SOHO/EIT 284 Å image. Yellow lines areclosed field lines; gray lines are open
field lines that connect to the ACE satellite.

From Liewer, Neugebauer, & Zurbuchen 2004, Solar Physics, 223, 209

11 December 2007 Active Region

EIT 171 Å ImageDo EIS upflows flow along open
field lines and contribute to the solar wind?

MWO Potential Field Extrapolation(Wang & Sheeley)

Conclusions: EIS Flows
•
•
•
•
•
•
•

Large non-thermal motions and outflows in active regions
occur in regions weak in intensity.
Line profiles are in some areas represent the superposition ofGaussians with different outflow speeds.
The outflow regions have QS temperatures of about 1.4 MK andelectron densities of about 5x108 – 1010 cm-3.
The outflow/turbulent regions are concentrated over magnetic
regions of primarily a single polarity and can last for at least a
day.
There are temperature variations within flow structures and amultiplicity of unresolved loops.
Some of the outflow plasma might occur in very long loops oralong open field lines that extend into the heliosphere.
Therefore, some of this flow might contribute to the solar wind.
At current spatial resolution, the connection of these outflows
to the photosphere and chromosphere will remain unclear. A
Plan B instrument can clarify the connection.

Active Region Coronal Loops

Single loop
strands?

Steady-stateheating models
can reproduce“hot” loops, but
fail to reproduce“warm” loops.

Or multi-loop
threads?

Sequential heatingin bundles of strands
reproduces “warm”
loops.

Cooling Coronal Loops from Active
Region 40” Slot Rasters from EIS

from Warren et al. 2008, 686, L131

Compute Line
EIS: Loop Filling Factors are ~ 10%
Intensities andWidthsCompute Emission
Electron Density
MeasureCompute Filling Factor

Fe XII 195.119 ÅAnalysis of 20 Loops

Loop Cooling: Evidence for Threads?

Predicted Cooling: 90s
Observed Cooling: 300s

EIS measures density
and temperature:
Cooling time
TRACE measures
Multithread
simulations
canapproximate
light
loop
evolution
curves, electron densities,
and DEMRed = TRACE, Green = EISFilling Factors of Coronal Bright Points
From Combined TRACE/EIS Observations
Right panel: histogram of inferred sub- resolution
bright point filaments. Filling factors are << 1. Spatial
resolution << 1” is needed to resolve structures andconnect bright points to the chromosphere. From Dere
2008, submitted to Astronomy &Astrophysics

Testing loop heating models such as the nanoflare model requires
spectroscopic temperature diagnostics, e.g., it is necessary to observeat high temperatures. From Warren et al. 2008, 685, 1277.
Note: Klimchuk, thismeeting

EIS and XRTSummary/Conclusions: Loops
•
•
•
•
•

•
•

Physical properties of loops in active regions, such astemperature, density, and dynamics, have been measured with aquantum improvement in spectral and spatial resolution with EIS.
Most “warm” loops (~1.4 MK) are not isothermal, but thetemperature distribution around the average is narrow.
Filling factors of dense warm loops are about 10%, supporting anunresolved strand model. Filling factors are inversely proportional
to loop pressure.
The combination of high densities and narrow temperatures
present challenges for understanding active region heating.
Warm loops appear to be loops that were heated up to higher
temperatures and are cooling. The cooling indicates thatunresolved strands are evolving coherently. Loop simulations are
consistent with this scenario.
It is highly desirable to connect the strands to their chromospheric/photospheric counterparts for testing loop heating models (hearVourlidas Ly-alpha talk)To make further progress, a Plan B-type instrument is required.

Solar Flare Reconnection Model – The“Standard Model”

from Hara et al. 2008
PASJ, 60, 275

This schematic “Standard FlareModel” provides theoretical guidance
for analyzing solar flare data.

Multi-Thread Simulation of the 5 January 1992 Flare

Numerical simulations
reproduce the BCS Yohkoh
light curves in the resonancelines of Fe XXV, Ca XIX, andS XV. A multi-thread model
can successfully account for
BCS light curves and spectra.
We can account for
chromospheric evaporation
with a multi-thread model.

from Warren & Doschek 2005, ApJ, 618, L157

Heavy Line: data
Light Line: modelA concept for a Plan B Telescope/Spectrometer. The NRL
Fine-Scale Advanced Coronal and Transition-region
Spectrograph (FACTS, Korendyke et al. 2008)

Entrance	
  Slit	  Gra4ng	  Telescope	
  Mirror	
  Focal	  Plane	  One possible concept. Separate telescopes arealso possible. FACTS technical challenge:
the primary mirror

FACTS Instrument Parameters••

Telescope: 60 cm usable diameter; 360 cm focal length; segmented into 4
quadrants with different coatings; high and matched spatial resolution from thephotosphere to the corona
UV/Visible bandpass: 2000 – 8000 Å––•

EUV1 bandpass: 170 – 210 Å; 330 – 370 Å (alternate)––•Spatial resolution - 0.14”/pixel
Spectral resolution - 0.050 Å/pixel

EUV3 bandpass: 1000 – 2000 Å––•

Spatial resolution - 0.1”/pixel
Spectral resolution - 0.010 Å/pixel

EUV2 bandpass: 500 – 1000 Å––•

Spatial resolution - ~0.2”/pixel
Spectral resolution - ~0.030 Å/pixel

Spatial resolution - 0.1” and 0.14”/pixel
Spectral resolution - ~0.060 Å/pixelTime resolution–––

A nominal 1s exposure gives reasonable counts in the brightest lines, especially inactive regions.
With a 1s exposure FACTS will produce a 60” x 200” image of the solar atmosphere in
300s, at 0.2” spatial resolution and full temperature coverage.
FACTS will produce 200” x 200” context images at 1” resolution in 20 s.

Fine-scale Advanced Coronal and Transition-region Spectrograph (FACTS)
C. Korendyke1, C. Brown1, G. Doschek1, E. Landi2, J. Karpen1, Y.-K. Ko1, J. Laming1, J. Mariska1, J. Morrill1, K. Muglach2, S. Patsourakos3, J. Seely1, I. Ugarte-Urra3, A. Vourlidas1 and H. Warren1
1 Naval Research Laboratory (Washington, DC), 2Artep, Inc. (Ellicott City, MD) 3George Mason University (Fairfax, VA)

Introduc4on	
  Gra4ng	  Observations

Entrance	
  Slit	  The FACTS optical design, coatings and detector
efficiencies have been combined to determine theinstrument collecting area in each channel. The
expected count rates were calculated for a 0.2" spatial
element. A nominal one second exposure gives
reasonable counts in the brightest lines, particularly inactive regions.

The	
  FACTS	
  mission	
  will	  determine	
  and	
  characterize	
  the	
  dominant	  	
  physical	
  processes	
  responsible	
  for	  the	
  structure,	
  dynamics,	
  and	  	
  evolu;on	
  of	
  the	
  upper	  solar	
  atmosphere.	
  These	
  physical	
  processes	  	
  drive	
  the	
  ﬂow	  of	
  mass	  and	
  energy	  through	
  the	
  solar	
  atmosphere	
  and	  
	  are	  at	  the	
  root	  of	
  space	
  weather	
  phenomena.	
  	
  Theore;cal	
  modeling	  	
  and	
  current	
  observa;ons	
  show	  that	  these	
  processes	
  generally	
  have	  	
  small	
  spa;al	
  scales,	
  drive	
  plasmas	
  over	  a	
  broad	
  temperature	
  range,	  	
  and	  are	
  oDen	
  intermihent	
  and	
  sporadic	
  in	
  nature.	
  	
  Focal	  Plane	  Deﬁni;ve	
  observa;ons	
  with	  the	
  following	
  characteris;cs	
  are	
  required:	  • broad	
  but	
  well	  diﬀeren;ated	
  temperature	
  coverage	
  to	
  comprehensively	
  observe	
  the	
  solar	
  atmosphere	
  and	
  follow	
  diﬀerent	
  structures	
  as	
  they	  evolve.	
  • measure	
  the	
  physical	
  proper;es	
  of	
  the	
  emiqng	
  plasma	
  -­‐	  	
  electron	  densi;es,	
  temperatures,	
  veloci;es,	
  abundances,	
  etc..	
  • suﬃcient	
  cadence	
  to	
  follow	
  the	  dynamic	
  evolu;on	
  of	
  the	
  structures	
  and	
  processes.	
  • suﬃcient	
  spa;al	  resolu;on	
  (<0.25″	
  )	
  	
  to	
  discern	
  individual	
  structures	
  and	
  approach	
  characteris;c	
  physical	
  scales	  suggested	
  by	
  theory	
  and	
  current	
  visible/UV	
  observa;ons.	
  Telescope	
  Mirror	
  Instrumentation
A preliminary design of the required instrumentation has been completed for the
purpose of sizing the overall resource requirements. This design has the following
important features:

Scien4ﬁc/technical	
  characteris4cs	
  of	
  the	
  
FACTS	  preliminary	
  design
Telescope design
parameters

Baseline or nominal value

Type

Single paraboloid mirror, each quadrant
coated for a particular EUV/UV/Vis
spectral range

optical properties

60cm usable aperture diameter, 360cm
focal length, <λ/80rms wavefront error
over each quadrant, <0.5nm
microrourghness, 17.5 microns/
arcsecond.

mirror blanklightweighted premium grade zerodur
blank (TBC), expansion class 0(<0.02x10-6 CTE).

mirror stabilization
mechanism

heritage design with voice coil actuatorsand integral feedback sensor, <0.03
arcsecond control, 15Hz bandwidth.

geometric blur~0.1" at 100" circular field of view,

Using the nominal exposure time, FACTS will produce
a 60" x 200" image of the solar atmosphere in 300
seconds, at 0.2" resolution with full temperature
coverage.
FACTS will produce 200"	
  x 200" context images of theupper solar atmosphere at 1" resolution in 20
seconds.

Calculated	
  Count	
  Rates	
  

Ion	
  

Wvlng	  (Å)	  Log	
  (T)	
  QS	
  cnts/s	
  

AR	
  or	
  FL	
  cnts/sec	
  

H	
  I	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
   1215.67	
  	
  	
  

4.04	
  

24,975	
  

241,316	
  

He	
  I	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
   584.34	
  

4.15	
  

71	
  

427	
  

C	
  II	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
   1335.71	
  

4.37	
  	
  	
  

599	
  	
  

40,795	
  	
  	
  

Si	
  III	
  

1206.50	
  

4.68	
  	
  	
  	
  

357	
  

1639	
  

He	
  II	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
   1640.35	
  

4.72	
  	
  	
  	
  

115	
  	
  	
  

3,589	
  •factor of ~10 improvement in light gathering power and spatial resolution overprevious instruments.
•simultaneous spectra across the EUV wavelength range.
•intrinsic spatial coregistration of the EUV, UV/Vis spectra and slit jaw images.

The	
  Naval	
  Research	
  Laboratory	
  is	
  presently	
  developing	
  a	
  next	  genera;on	
  solar	  spectrograph	
  to	
  meet	  these	
  requirements.	
  	
  The	
  
FACTS	
  instrument	
  combines	
  the	  UV	  diagnos;c	  capability	  of	
  CDS/SOHO,	
  SUMER/SOHO	  and	
  EIS/Hinode	
  with	  the	
  spa;al	  resolu;on	
  and	
  visible	
  light	
  imaging	  of	
  SOT/Hinode.	
  	
  FACTS	
  has	  	
  a	
  factor	
  of	
  10	
  more	  collec;ng	
  area	  and	
  spa;al	  resolu;on	
  than	  previous	
  EUV	
  instrumenta;on	
  and	
  broad	
  wavelength	
  coverage.	
  	
  	
  

Representa4ve	
  spot	  diagrams	
  for	  a	
  FACTS	
  gra;ng	
  geometry	
  in	
  the	
  EUV1	
  band.	
  	
  Three	  wavelengths	
  are	
  shown	
  185Å,	
  195Å	  and	
  205Å	
  with	  ﬁelds	
  of	
  0,	
  +50	
  and	
  +100	
  arcseconds	
  along	  the	  slit.	
  	
  Spot	  RMS	  is	  <6	
  microns.	
  	
  12	
  
micron	
  pixels	
  shown.	
  Other	
  bandpasses	
  have	  similar	
  performance.	
  •four separate wavelength bandpasses that yield unprecedented wavelength
coverage for a single instrument.
We envision achieving line of sight stabilization by active pitch/yaw tilt control of the
primary mirror. Similar systems with large optics have been built for JPL for theirplanetary cameras and have also been used in DoD. The error signal is provided by acorrelation tracker system built into the UV/Visible broadband filter imaging system.
This system is similar to that implemented for Hinode and other ground based
observatories.

The	
  FACTS	
  mission	
  will	  inves;gate	
  a	
  wide	  range	
  of	
  physical	  processes	
  in	
  the	
  solar	
  atmosphere.	
  These	  include	
  the	
  following:	
  • 	
  Characterize	
  and	
  determine	
  the	
  role	  of	
  waves	
  and	  reconnec?on	
  in	
  hea?ng	  the	
  solar	
  transi?on	
  region	
  and	
  corona.	
  Spectroscopic	
  diagnos?c	
  observa?ons	  at	
  the	
  relevant	
  spa?al	
  scales	
  will	  	
  discriminate	
  between	
  proposed	
  coronal	
  hea?ng	  mechanisms.	
  	
  • Follow	
  	
  the	  connec?vity	
  of	
  coronal	
  magne?c	
  ﬁelds	
  into	  the	
  chromosphere	
  and	
  photosphere.	
  Complementary	
  visible	
  light	
  observa?ons	
  and	
  spectroscopic	
  diagnos?cs	
  at	
  small	
  spa?al	
  scales	  are	
  ideally	
  suited	
  to	
  address	
  this	
  diﬃcult	
  issue.	
  • Follow	
  the	
  slow	
  and	
  fast	  solar	
  wind	  streams	
  to	
  their	
  origins.	
  Iden?fy	
  the	  source	  of	
  acous?c	
  and	
  Alfven	
  waves	
  that	  propagate	
  into	  the	
  heliosphere.	
  Most	
  relevant	
  RFAs:	
  	
  	
  
F1:	
  	
  Understand	
  magne;c	  reconnec;on	
  …	
  ﬂares,	
  CMEs,	
  …;	
  	
  	
  
F2:	
  	
  Understand	
  processes	
  …	
  that	  accelerate	
  …	
  par;cles;	
  	
  
H1:	
  	
  Understand	
  causes…solar	
  ac;vity	
  ...	
  that	  aﬀects	
  earth;	
  
J2:	
  	
  Develop	
  predic;on	
  capability	
  of	
  …	
  solar	
  ac;vity…;	
  FACTS	
  temperature	
  and	
  density	
  diagnos4cs	
  using	
  line	  intensity	
  ra4os.	
  Line	  ra;os	
  that	  involve	
  only	  lines	
  of	
  the	  same	
  ion	
  eliminate	
  uncertain;es	
  ;ed	  to	
  rela;ve	
  ion	
  abundances.	
  	
  The	
  plots	
  show	
  the	
  temperature	
  range	
  where	  each	
  ioniza;on	
  level	  is	
  formed.	
  	
  	
  The	
  lines	  indicate	
  where	
  the	
  frac;onal	
  abundance	
  is	
  larger	
  than	
  10%.	
  	
  Only	  the	  brightest	
  lines	
  of	
  each	  ion	
  were	  considered.	
  	
  FACTS	
  will	
  observe	
  the	
  en;re	  solar	
  atmosphere,	
  from	  photosphere	
  to	
  corona	
  with	  a	
  single	
  exposure.	
  	
  Electron	
  densi;es	  (Ne)	
  from	  106	  to	
  1012	
  cm-­‐3	
  can	  be	
  measured.	
  Effective areas (cm2) of the three channelsof FACTS, as a function of wavelength.

Candidate EUV optical coatings
for wavelengths above 50nm

Sample FACTS Science Topics•Theore;cal	
  intensi;es	
  calculated	
  using	
  CHIANTI,	
  except	
  for	
  H	
  I	
  
1215	
  Å	
  and	  He	  II	  1640	  Å,	
  where	
  observed	
  intensi;es	
  were	  used	
  
C	
  
III	
  	
  	
  	
  	
  	
  	
  	
  a
	
  	
  	
  vailable.	
  
	
  	
  
977.02	
  	
  	
  
4.84	
  	
  	
  	
  	
  
433	
  
1,716	  when	
  •These	  count	
  rates	  are	
  for	  a	
  pixel	  of	
  0.2"x	
  0.2".	
  With	  a	
  1"x	  1"	
  pixel	  the	
  count	
  rates	  increase	
  by	
  a	
  factor	
  25.	
  
Si	
  IV	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
   1393.76	
  	
  	
  	
  

The Million Degree CoronaThe	
  High	  Temperature	
  Corona	  Photospheric Drivers

Transition Region Moss and Loops

4.86	
  	
  	
  

57	
  	
  	
  

The	
  FACTS	
  Mission	
  

204	
  

The	
  complete	
  FACTS	
  instrument	
  is	
  straigh6orward	
  to	
  incorporate	
  into	  a	
  large	
  class	
  mission.	
  	
  The	
  heaviest	
  por;on	
  of	
  
the	
  
(telescope	
  mirror	  b95	  ulkhead)	
  
c241	
  
ould	
  be	
  mounted	
  
C	
  
IV	
  	
  	
  i	
  nstrument	
  
	
  	
  	
  	
  	
  
1548.19	
  
	
  	
  	
  	
  	
  	
  
5.02	
  
	
  	
  
directly	
  to	
  the	
  S/C	
  structure.	
  	
  The	
  instrument	
  op;cal	
  axis	
  will	  be	
  coaligned	
  to	
  the	
  spacecraD	
  ﬁne	
  sun	
  sensor.	
  	
  Preliminary	  resource	  requirements	
  are	
  given	
  in	
  the	
  following	
  table.	
  
N	
  V	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
   1238.82	
  	
  	
  
Instrument	
  resource	
  

5.26	
  

10	
  
30	
  
Preliminary	
  value	
  

O	
  V	
  

629.73	
  	
  	
  

5.37	
  	
  	
  	
  	
  

147	
  

383	
  

1031.91	
  	
  	
  	
  	
  	
  	
  

5.47	
  

146	
  
130-­‐160kg	
  

775	
  

Ac;ve	
  region	
  images	
  from	  Hinode/XRT	  and	
  TRACE	  •Active region loops with T ~ 3-5 MK appear steadyand disconnected from more variable cooler loops
that are rooted in the lower level fine structure(Moss).

O	
  VI	
  
mass	
  

Maps	
  of	
  intensity,	
  Doppler	
  shiD,	
  line	  width,	
  and	
  electron	
  density	
  from	
  EIS/Hinode	
  •Steady heating models require filling factors of about
10% to reconcile with observations. Moss studies
also suggest approximately 10% filling factors.

•

Are these hot active region loops bundles ofnanoflare heated filaments or are they steadily
heated?

•Nanoflare heated loops will show temporal evolution,
Doppler shifts from chromospheric evaporation, andlow densities.

••

Models	  suggest	
  ;me-­‐varying	
  and	
  impulsive	
  hea;ng	
  along	
  ﬁlamentary	  structures.	
  

•

The	
  detailed	
  temperature	
  distribu;on	
  within	
  coronal	
  loops	  is	
  not	
  well	  known.	
  ••FACTS will:

Loops	
  observed	
  near	  1	
  MK	
  are	  not	  in	
  equilibrium.	
  These	  loops	  have	  high	  densi;es,	
  show	
  strong	
  ﬂows,	  and	  are	
  evolving.	
  Resolve coronal loops attemperatures near 3 MK•

These	
  structures	
  undergo	
  rapid	
  evolu;on	
  and	
  change.	
  The	
  physical	
  processes	
  driving	
  this	
  ubiquitous	
  transient	
  behavior	
  (explosive	
  events,	
  blinkers,	
  etc.)	
  is	
  poorly	
  understood.	
  

•

The	
  coupling	
  of	
  the	  TR	  structure	
  to	
  the	
  upper	  and	
  lower	  atmosphere	
  is	
  the	
  key	  to	
  the	  transport	
  of	
  mass	  and	
  energy	  from	
  the	
  solar	
  interior	
  to	
  the	
  heliosphere.	
  •FACTS	
  will:	
  	
  	
  
–

obtain	
  detailed	
  spectroscopic	  observa?ons	
  of	
  transi?on	
  region	
  loops	  and	
  coronal	
  loop	  footpoints.	
  	
  

–

obtain	  simultaneous	
  co-­‐spa?al	
  measurements	
  in	
  the	
  corona	
  and	
  photosphere/
chromosphere.	
  FACTS	
  will:	  ––Transi;on	
  region	  (TR)	
  is	
  composed	
  of	
  footpoints	
  of	
  coronal	
  loops	  and	
  dynamic	
  loop-­‐like	
  structures	
  protruding	
  above	
  the	  chromospheric	
  canopy	
  (VAULT	  and	
  SUMER).	
  observe	
  the	
  internal	
  structure	
  of	
  coronal	
  loops	
  over	  a	
  broad	  range	  of	
  temperature.	
  SOT/Hinode	
  observa;ons	
  of	
  an	
  ac;ve	
  region:	
  	
  High	  resolu;on	
  Ca	
  II	
  H	
  (leD),	
  G	
  
Band	
  image	
  (right),	
  Stokes	
  V	
  magnetogram	
  (center).	
  
•

High	
  resolu;on	
  visible	
  observa;ons	
  show	
  the	
  magne;c	
  ﬁeld	  complexity	
  in	
  the	
  photosphere	
  and	
  chromosphere.	
  	
  These	  ﬁelds	  anchor	  the	
  magne;c	
  structures	
  in	
  the	  TR	  	
  and	
  corona.	
  	
  

•

Recent	  results	
  from	  SOT/Hinode	
  demonstrate	  the	
  wealth	
  of	
  the	  phenomena	
  such	  as	
  small-­‐scale	
  emerging	
  ﬂux,	
  forma;on	
  and	
  dynamics	
  of	
  sunspots	
  and	
  pores	
  and	  their	
  substructures	
  (e.g.	
  light	  bridges,	
  umbral	  dots,	
  Evershed	
  ﬂows)	
  as	
  well	  as	
  ubiquituous	
  waves	
  and	
  oscilla;ons.	
  	
  The	
  impact	
  of	
  these	  structures	
  on	
  the	
  upper	
  atmosphere	
  is	
  not	
  well	  understood.	
  •FACTS	
  will:	
  	
  	
  

Complementary	  instrumenta4on	
  ~0.2“ at 200" circular field of view
	
  	
  A	
  combined	
  mission	
  package	
  where	
  FACTS	
  is	
  accompanied	
  by	
  a	
  high	  resolu;on	  EUV	  context	
  imager	
  	
  	
  
	
  	
  would	
  be	
  par;cularly	
  powerful.	
  	
  This	  complement	
  would	
  combine	
  the	
  spectroscopic	
  measurements	
  of	
  
	
  	
  FACTS	  high	
  resolu;on	
  region	
  and	
  corona.	
  	
  FACTS	
  data	  set	
  will	  be	
  highly	
  
Ne	
  
VIII	
   with	  770.41	
  5.80	
  imaging	
  26	
   of	  the	  transi;on	
  
260	
  
	
  	
  complementary	
  to	
  exis;ng	
  ground	
  and	
  space	  based	
  observatories.	
  	
  The	
  spa;al	  resolu;on	
  of	
  FACTS	  is	
  op;cs	
  package	
  <80cm	  diameter,	  <420cm	  long	
   observatories.	
  	
  	
  comparable	  to	
  etnvelope	  he	
  next	  genera;on	
  solar	  ground	  based	  Technology	  development	
  
Fe	
  IX	
  
171.07	
  
5.80	
  	
  	
  	
  	
  
4	
  
31	
  
	
  	
  In	
  general,	
  the	
  technology	
  required	  to	
  implement	
  FACTS	  is	
  rela;vely	
  mature.	
  	
  Further	
  enhancements	
  to	
  
	
  	
  the	
  mission	
  implementa;on/science	
  could	
  be	
  achieved	
  with	  technical	  ollowing	  Slitimprovements	  assembly design in	
  the	
  fBaseline
or nominal value	  	
  areas.	
  	
  	
  
parameters
power	
  
<80W	
  
1)	
  	
  light	
  weight	
  mirror	  technology	
  and	
  line	  of	
  sight	
  stabiliza;on	
  mechanisms	
  for	
  half	
  meter	
  op;cs.	
  
Fe	
  X	
   2)	  	
  eﬃciency	
  174.53	
  	
  	
  a
	
   nd	
  durability	
  
6.00	
  	
  	
  	
  	
   of	  5	  broadband	
  
47	
  
EUV	
  coa;ngs.	
  
3)	
  	
  EUV	
  and	
  visible	
  detectors	
  especially	
  ac;ve	
  pixel	  sensors	
  and	
  solar	  blind	
  EUV	
  detectors.	
  4) high	
  quality	
  EUV	
  ellipsoidal	
  variable	
  line	  spaced	
  gra;ngs.	
  5) improvements	
  in	
  ACS	
  and	  TM	  related	
  spacecraD	
  technology	  (transmihers/receivers,	
  reac;on	
  General>5 slits and >3 slots of variable width,
	
  	
  	
  	
  	
  	
  	
  	
  	
  telemetry	  	  	
  wheels,	
  star	  trackers,	
  etc.).	
  0.6-­‐4Mbps,	
  depending	
  on	
  
Mg	
  X	
  

–

provide	
  observa?ons	
  of	
  comparable	  resolu?on	
  to	
  all	
  levels	
  of	
  the	  atmosphere	
  to	
  trace	
  the	  connec?ons	  between	  the	
  photosphere	
  and	  the	
  corona.	
  	
  –determine	
  the	
  small-­‐scale	
  topology	
  of	
  
the	
  photospheric	
  magne?c	
  ﬁeld	  from	  Stokes	  polarimetry	
  in	
  quiet	  Sun	
  and	
  ac?ve	
  regions.	
  	
  	
  

624.94	
  

6.05	
  	
  	
  

21	
  
382	
  
observing	
  modes	
  and	
  acceptable	
  compression	
  available for observation, front face withreflective coating,

References	
  > 200“ lengthT.	
  Shimizu,	
  S.	
  Nagata,	
  S.	
  Tsuneta,	
  T.	
  Tarbell,	
  C.	
  Edwards,	
  R.	
  Shine,	
  C.	
  Hoﬀmann,	
  E.	
  Thomas,	
  S.	
  Sour,	
  R.	
  Rehse,	
  O.	
  Ito,	
  Y.	
  Kashiwagi,	
  M.	
  Tabata,	
  K.	
  Kodeki,	
  M.	
  Nagase,	
  K.	
  Matsuzaki,	
  K.	
  Kobayashi,	
  K.	
  Ichimoto,	
  Y.	
  Suematsu,	
  ”	
  Image	
  Stabiliza;on	  Fe	
  XSystem	
  
I	
  
6.06	
  	
  	
   Solar	
  7	
   Op;cal	
  T98	
  f180.41	  or	
  Hinode	
  (Solar-­‐B)	
  elescope”,	
  Solar	  Physics	
  (Oct.	
  2007),	
  p.	
  154.	
  	
  Han	
  Uitenbroek,	
  Alexandra	
  Tritschler,	  Hyun	  Kyoung	
  An	
  and	
  Thomas	
  Berger,	
  “ The	
  visible	
  light	
  broad-­‐band	
  Imager	
  for	  ATST	
  orbit	  stable	  solar	
  view	  (sun	  synchronous,	  Preliminary	
  Design”,	
  Ground-­‐based	
  and	
  Airborne	  Instrumenta;on	
  for	  Astronomy,	
  edited	  by	
  Ian	  S.	
  McLean,	
  Masanori	
  Geo,	
  L1,	
  etc.)	
  with	  minimal	
  Iye,	
  Proc.	
  of	
  SPIE	  Vol.	
  6269,	  (2006).	
  eclipses.	
  Fe	
  XII	  	
  195.12	
  	
  	
  	
  

6.13	
  

9	
  

162	
  

Fe	
  XIII	  	
  202.04	
  

6.20	
  	
  	
  

2	
  

57	
  

Defined widths

0.1", 0.2", 0.5", 1“, rest – TBD

Solar Physics: Fundamental
Questions
1- What are the fundamental
structures of the solar
atmosphere?
2- What are the heating andenergy dissipation mechanisms
in the structures?
3- What drives extreme transient
events: flares and CMEs?

5,800 K
2.0 x 106 K
inner corona

2.0 x 106 K
solar wind

Solar “granules” orconvection cells nearsunspots in an active
region. Granules are about1000 km (~1.5”) in size.

1 x 105 K

The Extreme-ultraviolet Imaging
Spectrometer (EIS) on Hinode

EIS obtains high resolution spectra in two EUV wavebands:
170-210 Å and 250-290 Å. High optical reflectivity for thesewavebands is achieved using multilayer optics. Spectra can beobtained with narrow slits or with wider slots.
Sunlight passes through an Al filter and is imaged by anarticulated primary mirror onto either a slit or slot. The lightpasses through the slit/slot and is diffracted by a grating andfocused onto two CCD cameras. Below the green and pink referto the two wavebands.
EIS can measure the electron temperature and density, turbulence,and plasma flows in solar plasmas with unprecedented precision.

active region temperatures
movie
Fe XII intensity

active region dynamics
movie
electron density at 1.4 MK

The spatial resolution of EIS is 2” (1400 km) and the spectral
resolution is 0.0223 Å.

Hinode/EIS

Active Region Raster Data from Hinode/EIS

from Warren & Winebarger 2006, ApJ,
645, 711

Active Region ModelingTypical Large Flare Morphology and Evolution

Flares show a rising arcade of soft X-ray
emitting loops with a distribution oftemperatures and continuous energy
deposition.

The First Sign of Multi-million Degree Solar Flare
Loops
NRL BCS
spectra: Yohkoh

BCS
onset

How are coronal loops heated?
Plasma parameters are necessary to find out.
Current instrumentation cannot resolve multi-threaded coronal loops

from Aschwanden et al., ApJ, 659, 1673 (2007)

The 2006 December 17 Long
Duration Flare – EIS Spectra
Ca XVII (6 MK) intensity and nonthermal motions. Highspatial resolution is needed tounderstand the physics of thereconnection region. Are thenon-thermal motions true
turbulence, or are they due toa multiplicity of sub-resolution
loop “threads” that are moving
relative to each other?
Reconnection might be propagatedalong flare arcades via turbulence.
We need higher spatial resolution
to properly interpret theobservations.
From Hara et al. 2008, PASJ, 60, 275

The Dynamics of the Solar Transition Region

The dynamical connection between
the lower transition region (C IV, S V,
1.2 x 105 K) and the upper transition
region (Ne VIII 8 x 105 K) is very
unclear.

SUMER spectral images: Note the active
region complex in the lower left of eachintensity image above. This region ishighlighted in the upper left Doppler image.
Ne VIII contours are shown.

One Current View of the Transition region/Corona: We Need Plan B
to Test Chromosphere/Transition Region Models

from Peter, H., A&A, 374, 1108 (2001)