1. WG3: Extreme Events Summary N. Gopalswamy & A. Vourlidas

2. WG3 Questions 1.What can the extreme events tell us about the maximum free energy available in the source region? 2. How can we distinguish between CME and flare onsets? 3. Is a flare precursor a precursor or a preceding flare? (Same question for CMEs). 4. What is the relation between flare evolution and CME acceleration?

3. What WG3 discussed Historical Events October – November 2003 Events Energy Budget

4. Extreme Events Flare size  X10 CME speed (>2400 km/s) SEP intensity (>10 4 pfu) Sun-Earth shock transit time (< 24 h) Geoeffectiveness (Dst < -300 nT) Active Region Area (>1500 msh) Magnetic Energy (potential, free)

5. Event List & Data Base (Cycle 23) Flare size > X10 (5 events) Top 10 SOHO CMEs (Vcme > 2400 km/s) SEP intensity > 10 4 pfu (6 events) Top 5 Geomagnetic storms (Dst) http://cdaw.gsfc.nasa.gov/RST_Sonoma_WG3 /

6. GOES Flare Size >X10 2003/11/04 X28 CME 2001/04/02 X20 CME 2003/10/28 X17 CME SEP Dst Shock 2001/04/15 X14 CME 2003/10/29 X10 CME SEP Dst Shock  Two of the October events had multiple extreme properties

7. Relative Absence of Smaller Active Regions For Fast Transit Events 50% 32% 8% Sunspot Area Comparison for 3 Groups of Events Cliver, 2004 In Search of Major Solar Eruptions: Geomagnetic Storms (Aam* > 300 and/or Dst < -350) Fast Transit Events (< 22 hr Sun to Earth) Fast CMEs (> 2400 km s-1)

8. Hierarchy of Large Events -Fast (> 2400 km/s) CMEs: Often arise in moderate ARs -Eruptions Associated with Great Geomagnetic Storms: Larger ARs, More Energetic Eruptions (Compounding of Smaller Events May Cause Great Storms & Other Factors such as Season Play a Role) -Fast-Transit Events: Largest ARs, Most Energetic Eruptions (intense & long-lasting) Most Common Least Common Selection Effect: Only Most Energetic Events Maintain High Average Speeds to 1 AU Cliver, 2004

9. Historical Storms Carrington Event resulted in a -1620 nT storm. Real or some other ionospheric transient? How intense can storms get? Flare stars have energies in the range 10 37-39 erg Bmax = 0.047V -1.1 nT ~ 93 nT Tsurutani, et al. 2003

10. Empirical Shock Arrival Model 08/72 2850 km/s Carrington 2350 km/s Empirical Shock Arrival Model T = ab V +c October 2003 CMEs belong to the class of fast-transit events. There were only 11 Events reported since 1859 Gopalswamy et al., 2004 CME speed Limit?

11. AR Area vs Flares & CMEs log X = -8.34 + 1.50log A log V = 2.54 + 0.22log A Carrington flare had A ~ 2500 msh  Estimated GOES flare size: X6  Estimated speed of Carrington CME ~ 1850 km/s, Smaller than what ESA model value (2350 km/s) Gopalswamy et al., 2004

12. Mewaldt et al. 2004 The two cycle 23 events have similar spectrum Not too different from the famous August 72 event, except at low energy Feb 1956 event had very different spectrum

13. SEP energy is a significant fraction of the CME kinetic energy Electron energy is ~1-10% of the proton energy Mewaldt et al. 2004

14. Oct 28 flare2 October 28 2003 X17 flare and CME MC HXR sources Yurchyshyn, 2004 Helicity of the MC often agreed with the Active region helicity. The direction of the axial magnetic field in the MCs, are closely related to the direction of the axial magnetic fields in the associated post-flare arcades

15. Why Fast Halos? October November ARs were located close to open field lines, so the CMEs had larger speeds Synoptic maps show that 484 (464 in the previous rotation and 501 in the next rotation) had clear open field lines nearby Magnetic environment seems to control CME motion Y. Liu

16. Extreme Solar Flare Effects on the Ionosphere 30% increase in TEC in ~5 min (10/28/03) X-ray/EUV flare spectrum is highly variable: 11/4 larger in X-rays, but 10/28 larger in EUV Tsurutani

17. SEISMIC EMISSION FROM SOLAR FLARES Seismic emission from flares represents by far the most localized and episodic seismic radiation in the solar acoustic spectrum. Only a small fraction (~$10^-4$) of the total energy released in a large flare is appropriated into the acoustic spectrum. There is significant evidence that a major determinant of acoustic activity is the suddenness of the exciting impulse. Acoustic emission from flares could contribute to our understanding of wave propagation in magnetic chromospheres and photospheres. If properly understood, acoustic emission from flares could be a powerful probe of subphotospheric thermal anomalies and flows. Alina-Catalina Donea and Charles Lindsey

18. Relativistic Electrons 10/28 Event Precursor + pulse + main event + shock spike Precursor + pulse: ~E -5.3, E -6.6 Main Event: ~E -2 Shock spike: ~E -1.8 Shock spike and main event: scatter dominant Simnett

19. CME/Flare General Issues White Light Flare Problem is still open (e.g., are photospheric flares common?) CME & Flares are two manifestations of ONE dissipative phenomenon Dimensionless scaling should be used for classifications. Veselovsky

20. Flare/CME Relationship in Models Plausible mechanism: Loss of mechanical equilibrium plus magnetic reconnection. Reconnection is not a necessity for triggering the eruption, but it plays an essential role in the long-term evolution of the eruption. The correlation of flares to CMEs depends on the background field of the disrupting configuration: the stronger the background field, the better the correlation. Reconnection creates both the flare loop system and the expanding CME bubble. The resulting current sheet acts as an intermediary. In the sheared arcade & break-out models, flare always precedes the CME. For the catastrophe model, flare may occur at any stage depending of the details of the disrupting magnetic field. J. Lin

21. Oct/Nov 03: Speed, Width, Mass, KE The Oct/Nov CMEs were faster and wider on the average and hence more energetic This resulted in large number of shocks near the Sun and at 1 AU

22. CME & Flare Recurrence 1 5 6 Gopalswamy et al. 2004

23. Energetics E:\energetics.xls

24. Max Energies ------------------------------------------------------------ AR Area VB 2 p /8  Max KE (msh) (erg) (erg) ----------------------------------------------------------- AR0484 1750 3.66E+33 2.4e+32 AR0486 2610 4.57E+33 6.4e+32 AR0488 1750 2.76E+33 1.3e+32 ------------------------------------------------------------ 300” Regnier, Liu