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

A Catalog of Halo Coronal Mass Ejections from SOHO

N. Gopalswamy1, S. Yashiro2, G. Michalek3, H. Xie3, G. Stenborg2, A. Vourlidas4, R. A. Howard4

1NASA Goddard Space Flight Center2Interferometrics 3Catholic University

4Naval Research Laboratory

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 Workshop 22008 June 2-6 Gopalswamy

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 Workshop 32008 June 2-6 Gopalswamy

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


Halos: Similar to other CMEs, but selected by occulting diskHalo CME when AR on disk Normal CME when viewed sideways

2500 km/s 2700 km/s



Halo CMEs

Front-side halo back-side halo

Partial halo becomes asymmetric halo 6


Halo CMEs

Two halo CMEs headed earthwards

SEPs acceleration starts when theCME is close to the Sun (a few Rs)

SEPs reach SOHO (located along theSUN-Earth line at L1) in 10s of minutes

SOHO detectors blinded by SEPs

SOHO’s performance in imaging the coronais temporarily affected--Sometimes fatal


All CMEs (1996-2006)


UN/ESA/NASA/JAXA Workshop 8

Halos3.5%Wide

11.5%1052 km/s

Halo CMEs are faster on the average and wider


Halo CME PropertiesHalo CMEs, discovered in Solwinddata (Howard et al. 1982; 1985), have beenrecognized 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 theaverage CME.

Flares associated with halo CMEs arealso an order of magnitude more intense than the average soft X-ray flare

The high kinetic energy of the halos allowsthem to travel far into the interplanetarymedium and impact on Earthcausing geomagnetic storms.


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.




A Halo CME with SEP events & Shock at 1-AU

shock

Solar Location

Halo CME

SEP

Shock

Type II Burst (DH –km)

SSC11

The Halo CME Catalog


UN/ESA/NASA/JAXA Workshop12

URL: http://cdaw.gsfc.nasa.gov/CME_list/HALO/halo.html

Java Movie Frame



Javascript Movies Available for Analysis



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



CMEs and Geomagnetic Storms

CME headingTowards EarthHits EarthCauses big storm(Dst -260 nT)

CME moves westglancing blow causes moderate storm

CME on thebackside of the Sun.The CME does notreach EarthNo storm




Geoeffectiveness of Disk and Limb Halos


• 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%

Where do Halos originate from?

Halo sources are within 30 deg lat Mostly from Active regionsSlightly higher latitudes during solar minimum: effect of solar global field in polar coronal holes in pushing CMEs to the equatorial planeClosest 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

Coronal Hole Effects on CMEsDisk-center CME, but no ICME (only shock) Disk-center CME resulting in ICME + shock

CME is deflected away from the Sun Earth line CME is deflected towards the Sun Earth line19

Speed & Location



Halo CME speed vs. longitude. Non-geoeffective halos slower, and originate farther from the disk center.

CMEs of Cycle 23

CME speed < ~4000 km/s Limit to the Free energy available in active regions

CME population <V> km/s

All CMEs 471

metric II CMEs 610

MC CMEs 774

Geoeffective CMEs 1042

Halo CMEs 1052

mkm II CMEs 1500

SEP CMEs 1600

GLE CMEs 2000

11% of CMEs are wide (W ≥120o) ~1000Fast and wide CMEs ~500Halo CMEs ~500 (some are slower than 900 km/sMCs ~100; intense storms ~100; SEPs ~100

Gopalswamy, 2006

Sources of geoeffective & SEPeffective CMEs

N

S

WE

- 300nT < Dst < - 200 nT

Western 67%Eastern 33%SEP

Dst < -300 nTDst > -200 nT

Ip < 50 pfu

Ip 50 pfu

SEP sources Magnetic-storms sources

Disk center (W15) source for plasma impact; western CMEs for SEPs

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




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



What is a CME?A prominence eruption that becomesCME core (in microwaves, Nobeyama)

SOHO/LASCO sees the CMELater in the corona with the core

Brightening on the disk is the associated flare252008 June 2-6

Gopalswamy


Consequences of CMEs

• Drive shocks (SEPs, ESPs, Radio bursts, SSC, GLEs)

• (Ozone depletion, Cloud cover change)

• Induce Flares (SID, impulsive SEPs)

• Geomagnetic Storms: frontside halos262008 June 2-6

Gopalswamy

Documents

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