1. Multiwavelength Study of Solar Flares Chang Liu Big Bear Solar Observatory, NJIT
Seminar Day November 2, 2007

2. Contents # of Introduction Slides1 4 3
Introduction
Data source & Research methods/objects
Analysis I: “Shrinking Sunspot” …………..
Analysis II: 2003/10/29 X10 Flare ………….....
Analysis III: 2005/05/13 M8 Flare ..…………..
Analysis IV: 2005/09/13 Successive Flarings ..
Summary

3. Introduction
Solar flares are the manifestation of a sudden and intense energy release on the Sun, producing radiation in full electromagnetic spectrum from γ-rays to radio waves, and involving with magnetic fields in a wide range of scales from microflares to CMEs.
Major issue: How the magnetic energy is stored and released?
Many space-borne and ground-based instruments are available.
Detailed analyses of individual flares with multiwavelength data have promise to address the major issue.

4. Data Source & Methods/Objects
Current flare data source (partial): X-ray: RHESSI, GOES, SXI, XRT/Hinode EUV: TRACE 171/195, EIT/SOHO 171/195, EIS/Hinode UV: TRACE 1600 Visible: BBSO, GHN, OSPAN, SOT/Hinode Radio: OVSA, GBSRBS, WIND, etc.
Research methods/objects of solar flares (partial): 1. comparison of pre- and postflare morphology 2. fixed/running difference images 3. dynamic spectrum 4. hard X-ray/radio imaging/spectrum 5. magnetic reconnection rate 6. filament dynamics 7. coronal dimming and CME 8. photospheric magnetic field evolution and extrapolation 9. large-scale activities: remote brightenings, Moreton waves, etc. 10. long-term evolution of flaring region, e.g. sunspot rotation, EFRs

5. Analysis I: “Shrinking Sunspot”
(Liu et al. 2005, ApJ, 622, 722)
2001/04/06 X /04/09 M /08/25 X5.3
Conclusion: Rapid penumbral decay is a real physical process due to a permanent change of the field lines to a more vertical state after reconnection.

6. Analysis II: 10/29/2003 X10 Flare Conclusion:
1. Magnetic reconnection proceeds in two phases in this event
2. local hard X-ray footpoint motion might be the mapping of large-scale magnetic field restructuring, manifested as remote brightenings
(Liu et al. 2006, ApJ, 642, 1205)

7. Analysis III: 5/13/2005 M8 Flare
BBSO: 1"/pix fulldisk Hα, 0".6/pix hi-res Hα, 0".6/pix vector magnetograms, 0".6/pix hi-res Ca IIK, all with 1-min cadence
OSPAN: 1"/pix fulldisk Hα and wings with 1-min cadence
TRACE: 1600 Å with 3-sec cadence, 171 Å before and after flare
GOES12-SXI: 5"/pix P_THN_B SXR with 1-3 min cadence
RHESSI
OVSA, GBSRBS, Ondřejov, Potsdam, etc
SOHO/EIT, LASCO, MDI
(Liu et al. 2007a, ApJ, 669, 1372)

8. Sigmoid Explosion
Conclusion: Reconnection occurs within the sigmoid and eruption proceeds following the runaway tether-cutting model proposed by Moore et al. in 2001.

9. RHESSI HXR 25-50 keV; White Contours: TRACE UV ribbons
Ribbon-like HXR
* First reported RHESSI ribbon-like HXR sources
* Ribbon-like HXR is a theoretically expected, intrinsic feature of HXR emission.
RHESSI HXR keV; White Contours: TRACE UV ribbons
Conclusion: This “4 footpoint-to-2 ribbon” transformation of morphology of flare emission sources in both HXR and Halpha/UV should be related to the “sigmoid-to-arcade” transformation of the magnetic field configuration.
(Liu et al. 2007b, ApJL, 658, L127)

10. (Liu et al. 2007c, ApJL, in revision)
HXR Spectral Map
* Assuming local HXR spectrum in each pixel follows a power-law distribution in photon energy
* First reported RHESSI HXR spectral map
Conclusion: The finding of spatial analog of the well-known temporally soft-hard-soft spectral evolution pattern of the integrated HXR flux may provide further constraints on models of flare particle acceleration.
(Liu et al. 2007c, ApJL, in revision)

11. How complex “A” flare can be!
Analysis IV: 9/13/2005 Successive Flarings
NOAA/SEC only recorded this eruption as X1.5
How complex “A” flare can be!
(Wang et al. 2007, ApJ in press; Liu et al. 2007d, ApJ, in prep.)
X1.4
X1.5 M9
Two TRACE flux rope eruption, Two CMEs, Two type III busrsts + type IV and four pair of Halpha ribbons (see next) → NOT “A” single eruption, but a “Quadruple flare” within 100 minutes!

12. “Quadruple Flare”
Initial Flaring: evolving ribbons
Second Flaring: flux rope eruption + evolving ribbons
Third Flaring: flux rope eruption + evolving ribbons
Fourth Flaring: evolving ribbons
CME

13. RHESSI HXR is able to locate the later two flares
BBSO & OVSA have full coverage
RHESSI HXR is able to locate the later two flares
This ongoing study is aiming to synthesize BBSO Halpha, OVSA radio, TRACE, RHESSI HXR, and SOHO to probe the flaring mechanism.

14. Summary Flares exhibit themselves as a multiwavelength process.
Thus naturally, the eruption process of flares can be most reliably reconstructed combining multiwavelength data sets.
Detailed analysis of individual flare is necessary!
Flares can be very complicated (e.g., successive flarings), and ultimately understanding the embedded physics is challenging.