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First Baby Steps in Analyzing STEREO/EUVI Images

First Baby Steps in Analyzing STEREO/EUVI Images. Markus J. Aschwanden Jim Lemen, Jean-Pierre Wuelser, & Nariaki Nitta (LMSAL). 5th SECCHI Consortium Meeting University Paris-Sud, Orsay March 5-8, 2007. Content: EUVI Observing Sequence EUVI Cadence vs. GOES light curve

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First Baby Steps in Analyzing STEREO/EUVI Images

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  1. First Baby Steps in Analyzing STEREO/EUVI Images Markus J. Aschwanden Jim Lemen, Jean-Pierre Wuelser, & Nariaki Nitta (LMSAL) 5th SECCHI Consortium Meeting University Paris-Sud, Orsay March 5-8, 2007

  2. Content: EUVI Observing Sequence EUVI Cadence vs. GOES light curve EUVI full resolution images EUVI image compression GOES flare events: 2006/Dec-2007/Feb CME/occulted flare event 2007-Jan-24 14 UT Future EUVI data analysis goals Strategies for EUVI observations

  3. 1) Typical EUVI Observing Sequence 2007 Jan 24, 13-15 UT, spacecraft A=AHEAD Filename Date Time Instr Expos. Image size Wavelength UT time (s) NX*NY A IDL> datasum = SCC_READ_SUMMARY(date=‘2007-Jan-24…’, typ=‘img’, spa=‘a’, tel=‘euvi’)

  4. 2) Daily Observing Sequence vs. GOES Light Curve Both spacecraft A+B observe with a cadence of ~10 min in 171+195 A, and ~45 min in 284+304 A IDL>RD_GXD,’24-Jan-07 00:00’,’25-Jan-07 00:00’,goes_data IDL>SCC_READ_SUMMARY(date=‘…’,typ=‘img’,spa=‘a’,tel=‘euvi’)

  5. 3) Full resolution EUVI image Wavelengths: 171 A Image size: 2112x2048 Pixel size: 1.6” Field-of-view: 3240” +/-1.68 solar radii Dynamic range: 14 bit (2^14=16,384) Compression: ICER lossless (RICE) Exposure time: ~ 2 s Cadence: ~ 10 min

  6. Full field-of-view (1.6 R_sun) Partial image (zoom x 3)

  7. 195 A 171 A 304 A 284 A

  8. 4) Image Compression EUVI 171 A image Segment (East sector) i=0:512, j=831:1031 Flux profile F(i=0:512, j=931) DN Difference of flux profile between compressed ICER4 and lossless RICE dF=+/-2.7 … +/-4.7 DN Difference normalized by Poisson noise: dF/s=+/-0.8 … 0.6 (not significant !)

  9. EUVI 171 A image Segment (East sector) i=0:512, j=831:1031 Flux profile F(i=0:512, j=931) DN Difference of flux profile between compressed ICER6 and lossless RICE dF=+/-2.8 … +/-5.8 DN Difference normalized by Poisson noise: dF/s=+/-0.9 … 0.7 (not significant !)

  10. ICER 4: Difference dF/s=0.8…0.6 ICER 6: Difference dF/s=0.9…0.7 • No significant difference in compression quality

  11. EUVI 171 A image Difference normalized by Poisson noise: dF/s=-1 … +1 (black … white) ICER 4

  12. EUVI 171 A image Difference normalized by Poisson noise: dF/s=-1 … +1 (black … white) ICER6 shows no Significant differences to ICER 4 !

  13. 5) GOES Flare Events 2006-Dec … 2007-Feb EUVI-Ahead opens door on 2006-Dec-04 16:50 UT Frame #4 at 17:06:35 UT during C-class flare Flare rise time < 1 min, EUVI cadence=5 min Flare location undetermined in 171 A image

  14. 2006-Dec-09 10:50 UT GOES C-class flare Flare risetime <10 min EUVI cadence = 20 min Complex magnetic field configuration

  15. EUVI-Behind opens door at 2006-Dec-13 13:40 UT We missed 2 GOES X-class flares : 2006-Dec-13 03:00 UT 2006-Dec-14 22:00 UT

  16. GOES C-class flare 2006-Dec-31 07:00 UT Flare rise time < 10 min EUVI cadence A: 171,195=20 min, B: 195,304=5 min Quadrupolar double-arcade flare system

  17. GOES C-class flare 2007-Jan-10 08:00 UT Flare with loop-loop interactions GOES C-class flare 2007-Jan-10 10:55 UT with EUV jet --> open-closed loop interaction

  18. 6) CME/occulted flare : 2007-Jan-24 14:00 UT Flare location behind the limb (>10 deg) GOES soft X-ray flux starts to rise at 13:45 UT (occulted) EUVI shows a prominence at 14:22 UT (1 frame, 5 min cadence) LASCO observes CME front at 3 solar radii at 14:54 UT --> propagation speed v ~ 500 km/s

  19. Flare start ~ 13:35 UT AR loops are shaken by filament eruption and first brightening above limb, while flare location is occulted, GOES light curve starts to increase at 13:50 UT Flare peak ~ 14:05 UT AR loops are shaken strongest (damped oscillations ?), but all postflare loops are still occulted, GOES light curve shows steepest increase (HXR max) at 14:10 UT

  20. +2 hrs later: Postflare loop expands behind limb and the top of the arcade becomes visible +4 hrs later: Postflare loop system expands higher and EM of postflare loops still increases

  21. + 6 hrs: Post flare loops expand higher + 9 hrs:

  22. + 34 hrs: +38 hrs: loop densities decrease, longer cooling times

  23. 13:35 UT flare start (GOES increase, EUVI loop shaking) 14:05 UT flare peak (GOES steepest increase, EUVI loop oscillations) 14:22 UT: EUVI prominence/eruptive filament appears LASCO: CME front appears at >1 solar radii 15:00 UT: LASCO: CME front propagates > 3 solar radii with a speed of v~500 km/s 16:05 UT: EUVI: Postflare loop system appears above limb 18:15 UT: EUVI: Postflare loops h=19 Mm, v=2.4 km/s 20:15 UT: EUVI: Postflare loops h=40 Mm, v=2.6 km/s 23:15 UT: EUVI: Postflare loops h=70 Mm, v=2.7 km/s +34,38 hrs: EUVI postflare loop still visible h>100 Mm

  24. 7) Future EUVI Data Analysis Goals a) Determine 3D Magnetic field geometry at CME initiation site SoHO/LASCO Team

  25. b) Match up observed magnetic topology with flare models Kopp & Pneumann (1976), Hirayama (1974) Tsuneta (1997) Aulanier et al. (2000) • Magnetic reconnection has been successfully applied to solar flare events: • X-point geometry (cusp, conjugate simultaneity, Masuda sources) • Evolution (footpoint separation, height increase, loop shrinkage) • 3D geometry (bipolar, tripolar, quadrupolar, 3D fan, dome, spine) • Dynamics (reconnection inflows, outflows, waves) • Flare shocks (high-temperature slow shock ridge, fast-mode standing shock) • Ejecta (plasmoid ejecta) • Chromospheric heating (particle precipitation, conduction, evaporation)

  26. c) Identification of CME drivers: Sigmoids and Fluxropes • Twisted magnetic field lines • become unstable to the • kink-mode instability at • >1.5 turns • filament eruptions • confined eruptions Helicity of sigmoidal loops and eruptive filaments can predict helicity of Interplanetary fluxrope • CME magnetic field • geoeffective predictions Torok & Kliem (2004) Gary & Moore (2004)

  27. d) Disentangling the 3D geometry of twisted CME structures Dere et al. (1999) (Wood et al. 1999) Amary et al. (2003)

  28. e) Quantitative tests of CME kinematics Chen & Krall (2003) Gallagher et al. (2003) Quantitative measurement of altitude h(t), speed v(t), and acceleration a(t) Versus time allow us to test physical models of erupting CMEs and fluxropes.

  29. f) Study oscillatory dynamics after filament eruption or CME launch Aschwanden et al. (2001) Wang et al. (2003) McLean & Sheridan (1973) Verwichte et al. (2004)

  30. g) 3D modeling of dimming ``in CME evacuation corridor” Dere et al. (1997) Aschwanden et al. (1999) The ``coronal dimming’’ seen in EUV (T~1-2 MK) after launch of a CME Indicates the evacuation of coronal plasma behind the erupting CME and can be used to model the volume and 3D structure of the CME.

  31. 7) Strategies for synoptic EUVI observations Height-time h(t), velocity v(t), and acceleration a(t) measurements of erupting filaments and CME fronts often require a better cadence than 10 min to resolve changes of accelerating/decelerating forces that drive CMEs. (Gallagher et al. 2003)

  32. (Chen & Krall 2003) Quantitative tests of thephysics of CME initiation: require resolving changes in acceleration and deceleration of erupting filaments and CMEs higher cadence needed to measure 2nd time derivative to obtain the flux injection dF/dt in Chen’s model

  33. An erupting filament • or CME front clears • the EUVI FOV within • t=h/v~8-30 min • (h=500,000 km • v=300…1000 km/s) • With a typical EIT • cadence of 10 min • we miss all faster • CMEs and obtain • only ~2 images • for slow CMEs • insufficient context for modeling dimming (Dere et al. 1997)

  34. Flare-associated ejection & fast CMEs Alexander et al. (2002, GRL) C1 data suggest that there was a separate event starting ~1 hour before the main event (during a C2 data gap). • CME-like appearance • Fast acceleration • But CME already in the C2 FOV

  35. Propagation of EIT waves shows significant • propagation and evolution over 10 min • requires higher cadence to model time evolution of wave fronts and propagation (magnetoacoustic speed)

  36. Strategy 1)Fast-cadence 171 images: • Fast cadence of 2.5 min benefits science of • dynamic “CME initiation” phenomena • (filament eruption, dimming, EIT waves, etc. • velocity & acceleration measurements) • -Low 10-min cadence is insufficient to resolve dynamic • changes in EUVI FOV • (EIT missed most eruptive filaments or got only 1 frame) • -Fast cadence can be afforded with higher compression • (ICER6 uses a factor of 2 less telemetry than ICER4) • Difference in photon statistics of ICER6 vs. ICER4 • is not significant !

  37. Strategy 2: High cadence in 171 A rather than 195 A: • 171 TRACE movies show filament eruption (in absorption) very well at <1.1…1.2 solar radii • during initiation of CME • AR (loop) structures are crispier in 171 than in 195 A, during pre-CME conditioning. • EIT has tracked EIT waves dominantly in 195 A, • but there is no statistical evidence that EIT • waves are better detected in 195 A than in 171 A

  38. Conclusions: • Current focus in developing EUVI data analysis software : - Image quality (compression, exposure time, cadence) - Image calibration (flatfielding, flux-EM conversion, intercalibration) - Image coalignment (spacecraft pointing, roll angle correction) - Visualization (browser, movies, overlays; FESTIVAL, PANORAMA) - 3D Geometric reconstruction from 2 stereoscopic views • Data analysis during first 3 months (Dec 2006-Feb 2007): - Stereoscopic separation angle <1.2 deg at March 1, 2007 - EUVI observed 1 CME (2007-02-14) and about a dozen C-flares - shaking and damped oscillations of coronal loops at CME launch - quiescent and erupting filaments/prominences - bipolar, tripolar (jets), and quadrupolar flare configurations - evolution of postflare loop systems Strategy of future EUVI synoptic observations: - increase cadence of 171 A from 10 min to 2.5 min - choose 171 for fast cadence rather than 195

  39. New EUVI website: http://secchi.lmsal.com/EUVI/

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