Imaging Solar Coronal Structure With TRACE

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Imaging Solar Coronal Structure With TRACE
TRACEhttp//vestige.lmsal.com

• Leon Golub, SAO

ISAS - 4 Feb. 2003
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The SAO Solar-Stellar X-ray Group
http//hea-www.harvard.edu/SSXG/

• Leon Golub
• Jay Bookbinder
• Ed DeLuca
• Mark Weber
• Joe Boyd
• Paul Hamilton
• Dan Seaton
• With results from A. Van Ballegooijen, A.
  Winebarger and H. Warren

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The Major Coronal Physics Problems

• 1. Why is the corona hot?
• 2. Why is the corona structured?
• 3. Why is the corona dynamic unstable?
• Emergence of B into the atmosphere,
• and response to B.

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Why Use X-rays to Observe Corona?
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Response to flux emergence
1. Vigorous EFR Dynamics. 2. Large-scale B
adjustment. 3. Strong local heating.
(30-second cadence for 24 hours)
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Outline of Talk
Loops What TRACE sees a. Non-hydrostatic
loop controversy what are we really
seeing? b. Moss and transient vs. steady
heating. c. Hot vs. cool material in ARs
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Heating Dynamics in ARs
TRACE sees four (or possibly only three) distinct
processes in active regions 1. Steady outflows
in long, cool structures. ? 2. Transient loop
brightenings in emerging flux areas. Also hot
cool material intertwined May or may not be
related to TLBs. 3. Steady heating of hot loops
(moss). ? 4. Flare-like events at QSLs (or may
be cooling events predicted by 3.).
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Examples of all four phenomena
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Another example of flows
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Same region next day(ignore the little flares
nearby!)
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TRACE Active Region Observations are not
Consistent With Hydrostatic Model
Figure from Aschwanden et al. 2000
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Non-HS Loops are ubiquitous
courtesy H. Warren
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Partial Listing of Recent Papers About
Non-Hydrostatic Loops

• Lenz etal 1999, ApJ, 517, L155.
• Aschwanden etal 2000, ApJ, 531, 1129.
• Winebarger etal 2001, ApJ, 553, L81.
• Schmelz etal 2001, ApJ, 556, 896.
• Chae etal 2002, ApJ, 567, L159.
• Testa etal 2002. ApJ, 580, in press.
• Martens etal 2002, ApJ, 577, L115.
• Schmelz 2002, ApJ, 578, L161.
• Aschwanden 2002 ,ApJ, 580, L79.
• Warren etal 2003, ApJ, submitted.

• Small gradient in filter ratio, high n.
• Multithread model (a la Peres etal 1994, ApJ 422,
  412), footpoint heating.
• Flows and transient events in non-hydrostatic
  loops.
• DEM spread ? const. filter ratio.
• More passbands may help.
• Large range in thread T for some loops.
• Full DEM need at each point.
• Grad T along loops w/flat filter ratio
• Contra Martens.
• Repeated heating episodes.

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What Needs to be Explained?

• 1. 195A/173A ratio is flat.
• 2. Emission extends too high for hydrostatic loop
  (this is debated, though).
• 3. Loop density is high by an order of magnitude.
• 4. Apparent flows (and some Doppler shifts
  measured).

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Active Region 8536
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How isothermal are these loops?
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SUMER Velocities
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Symmetric vs. Asymmetric Heating
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Static vs. Flow Model
Winebarger etal ApJL (2001)
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Best fit vs. Uniform heating
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High-Conductance Model withAsymmetric Heating
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The Effect of High Conductivity
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Footpoints in Transient Heating
1. Initial energy release along current
sheet (spotty) 2. Footpooint brightening. 3.
Evaporation, then post-flare loops.
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Comparison Evaporative Model vs.TRACE Obs.
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Moss as TR of Hot Loops
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Heating Shut-off vs. Observations
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Using FLASH to model coronal loops

• FLASH is a state-of-the-art simulator code for
  solving thermonuclear/astrophysical problems.
• FLASH is funded under the DoE ASCI/Alliances
  Program.
• SAO study of coronal loops with FLASH is in
  collaboration with the Palermo Astronomical
  Observatory, with technical support from the
  FLASH Center.

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FLASH The coronal loop application

• One-dimensional, vertical, semicircular loop with
  half-length of 100 Mm
• Boundary conditions T 20,000 K
  ne 1010
• Hydrodynamic model ionized hydrogen plasma
  gravity Spitzer conductivity and radiative
  cooling (Raymond Smith, 1977 Raymond, 1978)

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Stability regime diagramAsymmetric footpoint
heating scale height vs. loop length

• Solution points from a code by van Ballegooijen
  (not published). The corresponding results for
  symmetric heating give a virtually identical
  stability boundary.
• For comparison, the plotted lines indicate the
  stability thresholds predicted for symmetric
  footpoint heating. The van Ballegooijen results
  (for both symmetric and asymmetric heating) are
  more consistent with the Serio et al. line.
• The boxes indicate stable, converged FLASH trial
  solutions. The leftmost box is not consistent
  with the van Ballegooijen results.

Unstable regime
Steady-state regime
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FLASH solution, point 1sH 39.8 Mm

• Steady siphon flow
• Initial condition corresponding steady-state
  solution from van Ballegooijens code

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FLASH solution, point 2sH 25.1Mm

• Steady siphon flow
• Initial condition corresponding steady-state
  solution from van Ballegooijens code

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FLASH solution, point 3sH 15.8 Mm

• Steady siphon flow
• Initial condition steady-state solution from van
  Ballegooijens code for point 2, because
• van Ballegooijens code does not converge to a
  steady-state solution for point 3, in contrast
  to FLASH, which does reach steady-state

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Further work with FLASH

• Currently running more solution points in
  sequence shown on stability plot in order to
  locate the instability threshold for a loop with
  half-length 100 Mm.
• We are collaborating with the Palermo
  Astronomical Observatory to investigate dynamic
  behavior of both symmetrically and asymmetrically
  heated loops.
• Q will we be able to reproduce observed
  non-linear behaviors of hot and cool material
  flowing together in TRACE active region loops?

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Microscale B vs. X
1. Complex relation between photosphere
and corona. 2. Very rapid dynamics. 3. Large
T-range to be observed.
Resolution requires Solar-B observations!
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New View of Coronal Structures
Hot Plasma
ß1
?
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Hot Material in the Corona
Mg XII Ly-a superposed on Fe X (log T 6.9 and
6.0)
Consistent with RHESSI detection of
non-thermal electrons in quiescent active
regions.
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TRACE Flare Results

• TRACE observes Fe XXIV 192 Å highest resolution
  images ever of hot flare plasma
• Qualitatively consistent with flare models hot
  loops form first, cool post-flare loops form
  later
• Evidence for hot regions 20 MK plasma is
  found above 10 MK flare arcades
• Fine structure in flares simulations with many
  small loops are needed to reproduce the
  observations
• Pre-Flare observations evolution of ribbon
  brightenings is complex

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A Typical Event
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July 25, 1999 M2.4 Limb Flare
Warren etal., ApJLett, 1999.
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Most of the Flare Emission is Near 10 MK June
25, 1999 M2.4
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SXT and TRACE Show 15-20 MK Loop-Top Plasma
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March 24, 2000 X1.8 Flare1600 Å and 195 Å Movies
Warren Reeves, ApJLett (2000).
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March 24, 2000 X1.8 Flare195 Å Near SXR Peak
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March 24, 2000 X1.8 Flare195/171 Filter Ratios
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Reconnection at top of flares
1. Flare heating is preceded by expansion of high
loops. 2. Hi-T source above postflare loops.
? 3. Hi-T coincident with footpoint ribbon
heating. 4. Source moves upward during course of
flare. ?
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Modeling the Evolution of the Flare Arcade (2D)
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Comparisons With SimulationTRACE 195/171 Filter
Ratios
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Improved Fit with Taller Loops
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END PRESENTATION
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March 17, 2000 M1.1 TRACE 1600 Å Movie
Warren Warshall,ApJL (2001)
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March 17, 2000 M1.1 TRACE 1600 Å Images
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March 17, 2000 M1.1 TRACE 1600 Å Light Curves
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TRACE Footpoint vs. BATSE HXR
?HESSI!
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The Solar-B Mission
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The Solar-B Instrument Complement
1. Solar Optical Telescope with Focal Plane
Package (FPP) - 0.5m Cassegrain, 480-650nm - VMG,
Spectrograph - FOV 164X164 arcsec 2. EUV Imaging
Spectrograph (EIS) - Stigmatic, 180-204,
240-290Å - FOV 6.0X8.5 arcmin 3. X-ray Telescope
(XRT) - 2-60Å - 1 arcsec pixel - FOV 34X34 arcmin
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XRT vs. SXT Comparison
1. Higher spatial resolution 1.0 vs. 2.5 2.
Higher data rate 512kB continuous. 3. Ten focal
plane analysis filters. 4. Extended low-T and
high-T response. 5. FIFO buffer for flare-mode
obs.
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Science Themes

• Plasma Dynamics
• Thermal Structure and Stability
• The Onset of Large Scale Instabilities
• Non-Solar Objects

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Plasma Dynamics

• Reconnection
• loop-loop interaction
• flux emergence
• nano-flares
• AR jets
• macro-spicular jets
• filament eruption

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Plasma Dynamics

• Waves
• origin of high speed wind
• tube waves
• coronal seismology

Figures from Nakariakov et al. (1999) decaying
loop oscillations seen in TRACE can be used to
estimate the coronal dissipation coefficient. Re
6 x 105 or Rm 3 x 105 , about 8 orders of
magnitude less than classical values.
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Thermal Structure/Stability

• Physical Properties
• Te, ne, EM
• energetics
• variability timescales
• Multithermal Structure
• steady loops
• filaments

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Onset of Large Scale Instabilities

• Emerging Flux Region
• twisting/untwisting
• reconnection
• delta Spots
• current sheets
• topology changes
• Active Filaments
• Te, ne
• local heating

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Non-Solar Objects

• Jupiter
• S VII _at_ 198
• Nearby RS Cvns
• Galaxy Cluster Halos
• Comets
• Any EUVE source within 1 deg of Sun

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Science Drivers I Spatial Scales
105 km 103 km 101 - 103 km lt10
km lt10 km

• Global MHD Scales
• Active Regions
• granulation scales
• Transverse scales
• - dT, dn
• - dB and j
• Reconnection sites
• location
• size
• dynamics

RAM discovery space
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Science Drivers II Time Scales

• 10 sec
• 100 sec
• 1 - 10 sec
• 10 - 100 sec
• 1 - 100 sec
• minutes - months

• Loop Alfven time
• Sound speed vs. loop length
• Ion formation times
• Plasma instability times
• Transverse motions
• Surface B evolution times

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Optics Metric