1. A Catalog of Halo Coronal Mass Ejections from SOHO N. Gopalswamy 1, S. Yashiro 2, G. Michalek 3, H. Xie 3, G. Stenborg 2, A. Vourlidas 4, R. A. Howard 4 1 NASA Goddard Space Flight Center 2 Interferometrics 3 Catholic University 4 Naval Research Laboratory

2. Plan of the Talk CDAW Data Center What are Halo CMEs? Why Catalog Halo CMEs? A Brief Description of the Catalog Geoeffectiveness of Halos Solar Energetic Particles and Halo CMEs Summary UN/ESA/NASA/JAXA Workshop22008 June 2-6 Gopalswamy

3. CDAW Data Center The CDAW Data Center (http://cdaw.gsfc.nasa.gov) is a repository of coronal mass ejection (CME) data sets useful to the Heliophysics community Contains value-added data products on CMEs detected by SOHO/LASCO. The SOHO/LASCO CME catalog is linked to the Virtual Solar Observatory (VSO). The Halo CME Catalog is a new data product focusing specifically on halo CMEs known to have significant impact on Heliospace including Space Weather. UN/ESA/NASA/JAXA Workshop32008 June 2-6 Gopalswamy

4. UN/ESA/NASA/JAXA Workshop What are Halo Coronal Mass Ejections? CMEs that appear to surround the occulting disk in sky-plane projection (Howard et al. 1982) Halos are no different from other CMEs, except that they must be faster and wider on the average to be visible outside the occulting disk Halos affect a large volume of the corona Most of the halos may be shock-driving Most halos are geoeffective (70%) 42008 June 2-6 Gopalswamy

5. UN/ESA/NASA/JAXA Workshop Halos: Similar to other CMEs, but selected by occulting disk Halo CME when AR on diskNormal CME when viewed sideways 2500 km/s2700 km/s 5 2008 June 2-6 Gopalswamy

6. UN/ESA/NASA/JAXA Workshop Halo CMEs Front-side halo back-side halo Partial halo becomes asymmetric halo 6

7. UN/ESA/NASA/JAXA Workshop Halo CMEs Two halo CMEs headed earthwards SEPs acceleration starts when the CME is close to the Sun (a few Rs) SEPs reach SOHO (located along the SUN-Earth line at L1) in 10s of minutes SOHO detectors blinded by SEPs SOHO’s performance in imaging the corona is temporarily affected --Sometimes fatal 72008 June 2-6 Gopalswamy

8. All CMEs (1996-2006) 2008 June 2-6 Gopalswamy UN/ESA/NASA/JAXA Workshop8 Halos 3.5% Wide 11.5% 1052 km/s Halo CMEs are faster on the average and wider

9. UN/ESA/NASA/JAXA Workshop Halo CME Properties Halo CMEs, discovered in Solwind data (Howard et al. 1982; 1985), have been recognized in the SOHO era as an important subset relevant for space weather Only ~3.5% of all CMEs are halos Halos are ~ 2 times faster than the average CME. Flares associated with halo CMEs are also an order of magnitude more intense than the average soft X-ray flare The high kinetic energy of the halos allows them to travel far into the interplanetary medium and impact on Earth causing geomagnetic storms. 92008 June 2-6 Gopalswamy

10. Why Catalog Halo CMEs? Most of the halos may be shock-driving. 70% halos are geoeffective when frontsided (Gopalswamy et al. 2007). Halo CMEs are the main sources of severe space weather at Earth. They are important to study the solar connection because most of the magnetic clouds are due to Halo CMEs. Halo CMEs represent one of the most energetic CME populations. 2008 June 2-6 Gopalswamy UN/ESA/NASA/JAXA Workshop10

11. UN/ESA/NASA/JAXA Workshop A Halo CME with SEP events & Shock at 1-AU shock Solar Location Halo CME SEP Shock Type II Burst (DH –km) SSC 11

12. The Halo CME Catalog 2008 June 2-6 Gopalswamy UN/ESA/NASA/JAXA Workshop 12 URL: http://cdaw.gsfc.nasa.gov/CME_list/HALO/halo.html

13. Java Movie Frame 2008 June 2-6 Gopalswamy UN/ESA/NASA/JAXA Workshop13

14. Javascript Movies Available for Analysis 2008 June 2-6 Gopalswamy UN/ESA/NASA/JAXA Workshop14

15. Geoeffectiveness of Halos The ability to produce significant geomagnetic disturbances (e.g., Dst ≤ - 50 nT) Front-sided halos originate close to disk center of the Sun, so they are likely to hit Earth Off-centered halos produce moderate storms 2008 June 2-6 Gopalswamy UN/ESA/NASA/JAXA Workshop15

16. CMEs and Geomagnetic Storms CME heading Towards Earth Hits Earth Causes big storm (Dst -260 nT) CME moves west glancing blow causes moderate storm CME on the backside of the Sun. The CME does not reach Earth No storm 162008 June 2-6 Gopalswamy UN/ESA/NASA/JAXA Workshop

17. Geoeffectiveness of Disk and Limb Halos 172008 June 2-6 Gopalswamy Frontside Halos are highly geoeffective (average Dst = -117 nT) Frontside Off-Limb halos (Flimb) are moderately geoeffective (average = -72 nT) Backside halos (including near the limb) are not geoeffective (average = -43 nT) Knowing the source location of the halo CMEs is important 75% 60%

18. Where do Halos originate from? Halo sources are within 30 deg lat  Mostly from Active regions Slightly higher latitudes during solar minimum: effect of solar global field in polar coronal holes in pushing CMEs to the equatorial plane Closest to the equator during the declining phase (butterfly pattern) Non-geoeffective halos also originate close to the disk center  additional factors that decide geoeffectiveness 18 RISE MAX DECL

19. Coronal Hole Effects on CMEs Disk-center CME, but no ICME (only shock)Disk-center CME resulting in ICME + shock CME is deflected away from the Sun Earth lineCME is deflected towards the Sun Earth line 19

20. Speed & Location 2008 June 2-6 Gopalswamy UN/ESA/NASA/JAXA Workshop20 Halo CME speed vs. longitude. Non-geoeffective halos slower, and originate farther from the disk center.

21. CMEs of Cycle 23 CME speed < ~4000 km/s  Limit to the Free energy available in active regions CME population km/s All CMEs471 metric II CMEs610 MC CMEs774 Geoeffective CMEs1042 Halo CMEs1052 mkm II CMEs1500 SEP CMEs1600 GLE CMEs2000 11% of CMEs are wide (W ≥120 o ) ~1000 Fast and wide CMEs ~500 Halo CMEs ~500 (some are slower than 900 km/s MCs ~100; intense storms ~100; SEPs ~100 Gopalswamy, 2006

22. Sources of geoeffective & SEPeffective CMEs N S WE - 300nT < Dst < - 200 nT Western 67%Eastern 33% SEP Dst < -300 nT Dst > -200 nT Ip < 50 pfu Ip  50 pfu SEP sourcesMagnetic-storms sources Disk center (W15) source for plasma impact; western CMEs for SEPs

23. Summary of the Catalog The Halo CME Catalog contains all the Halo CMEs identified in the SOHO/LASCO Data (1996- to date). Most information available in the general CME catalog is also available for halo CMEs. In addition, heliographic coordinates of the source from which the Halo CMEs erupt, the soft X-ray flare importance, and the flare onset time are included. In the near future, deprojected speeds will be included. This catalog is useful to the LWS and Space Weather communities; Will be accessible from VSO site. URL: http://cdaw.gsfc.nasa.gov/CME_list/HALO/halo.html 2008 June 2-6 Gopalswamy UN/ESA/NASA/JAXA Workshop23

24. UN/ESA/NASA/JAXA Workshop Science Conclusions Halos constitute ~3.6% of all CMEs (11% when partial halos included). Halo CMEs, as a class, are more energetic are and associated with bigger soft X-ray flares. Halos have a much higher rate during maximum phase of the solar cycle Halos originate mostly in the active region belt There is a center-to-limb decline of geoeffectiveness: about 75% of the disk halos and 60% of limb halos are geoeffective. Geoeffectiveness also depends on the speed of the CMEs 242008 June 2-6 Gopalswamy

25. UN/ESA/NASA/JAXA Workshop What is a CME? A prominence eruption that becomes CME core (in microwaves, Nobeyama) SOHO/LASCO sees the CME Later in the corona with the core Brightening on the disk is the associated flare 252008 June 2-6 Gopalswamy

26. UN/ESA/NASA/JAXA Workshop Consequences of CMEs Drive shocks (SEPs, ESPs, Radio bursts, SSC, GLEs) (Ozone depletion, Cloud cover change) Induce Flares (SID, impulsive SEPs) Geomagnetic Storms: frontside halos 262008 June 2-6 Gopalswamy