SOHO 20

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Halo coronal mass ejections and proton events
during solar cycle 23
SOHO 20 - Transient Events on the Sun and in the
Heliosphere

• P. Mäkelä1,2, N. Gopalswamy2, S. Yashiro1,2,
• S. Akiyama1,2, and E. Valtonen3
• Catholic University of America, USA
• NASA/Goddard Space Flight Center, USA
• Space Research Laboratory and Väisälä Institute
  for Space Research and Astronomy, Finland

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Earth-directed CMEs

• 10 of CMEs hit the Earth
  (e.g., Webb and Howard 1994)
• 50 of frontside CMEs with widths gt140
  encounter the Earth (Cane et al., 2000)
• 71 of frontside full halo CMEs are
  geoeffective (GE) (Gopalswamy et al., 2007)
• Dst-index
• Weak storm -30 nT lt Dst -50 nT
• Moderate storm -50 nT lt Dst lt -100 nT
• Severe storm Dst -100 nT
• CMEs causing strong storms originate more likely
  from the western hemisphere (Zhang et al., 2003)

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Halo CMEs are inherently fast
(Gopalswamy et al. 2007 JGR)
Limb halos are 66 faster than disk halos ?
projection effects
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Correlations

• CME speed and Solar Energetic Particle (SEP)
  intensity correlate (e.g., Kahler,1978
  Reames, 1999)
• Scatter still large (Kahler, 2001)
• CME speed and geoeffectiveness correlate (e.g.,
  Srivastava et al., 2002)
• Halo CME rate and SEP event rate correlate (e.g.,
  Valtonen, 2006)

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Data

• Gopalswamy et al. 2007
• LASCO list of full halo CMEs in 1996-2005
  (total of 378), flare location and Dst index
  (World Data Center in Kyoto)
• SOHO/ERNE proton intensities
• 1.8 - 80 MeV in six energy channels
• Storm Sudden Commencement (SSC)
• Solar Geophysical Data
• Shock times
• SOHO/Proton Monitor (http//umtof.umd.edu/pm)
• ACE/SWEPAM and MAG (http//www.bartol.udel.edu/ch
  uck/ace/ACElists/obs_list.html)

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SEPeffectiveness

• 180 (51) of analysed 354 halo CMEs had
  observable proton event.
• 135 proton events associated with a frontside
  halo CME 63 of all frontside halo CMEs.
• 45 proton events associated with a backside CME
  32 of all backside halo CMEs (20 behind limb
  CMEs).

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Source location, geoeffectiveness and
SEPeffectiveness
Average longitude Moderate E09 Severe W06
Average longitude Moderate E02 Severe W11

• 40 (67) moderately and 55 (63) strongly GE
  frontside CMEs associated with a proton event.

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SEP Storm Sources
Gopalswamy et al. 2005
SEP source
Storm source
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• SEPs
• Moderate1217 km/s
• Severe 1284 km/s
• No SEPs
• Moderate 823 km/s
• Severe 757 km/s

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SEPs with Energetic Storm Particle (ESP) event
with shock/SSC
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ESP
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Sources without ESP
but possibly with shock/SSC
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Peak intensities
Moderate
Severe
2.7-5.1 MeV
12.7-22.1 MeV
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Longitudinal dependence
Moderate
Severe
2.7-5.1 MeV
12.7-22.1 MeV
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Speed dependence
Moderate
Severe
C0.62
C0.46
2.7-5.1 MeV
C0.66
C0.14
12.7-22.1 MeV
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Conclusions

• Conducted a statistical study of 354 halo CMEs
• 51 of geoeffective CMEs associated with a
  proton event.
• 63 of all frontside halo CMEs associated with
  a proton event
• 32 of all backside halo CMEs associated with
  a proton event
• Proton events by strongly GE CMEs are more likely
  intense and originate from the western hemisphere
  than proton events by moderately GE CMEs
• Strongly GE CMEs with a SEP and ESP event
  originate west from solar central meridian,
  moderately GE CMEs with a SEP and ESP event east
  from the central meridian.

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THE END
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Forecasting

• 47-65 keV ion enhancements
• Together with halo CME observations improve
  prediction of geoeffectiveness (Smith et al.,
  2004)
• 1-110 MeV protons
• Improves frontside/backside CME separation.
  Travel time proxy correlates with storm strenght.
• Specific SEP signatures ambigious
  reduced prediction efficiency. (Valtonen et al.,
  2005)
• E 10 MeV SEP enhancements
• Better than speed as an indicator of
  geoeffectiveness (Gleisner 2006).

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SEP-associated CMEs
Gopalswamy et al. 2005
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Background

• Gradual Solar Energetic Particle (SEP) event
• CME associated shock accelerates particles
  (Reames 1999)
• Time profiles highly variable
• Geomagnetic storm
• Interplanetary magnetic field southward for an
  extended period of time
• Depression in Dst-index
• Weak storm -30 nT lt Dst -50 nT
• Moderate storm -50 nT lt Dst lt -100 nT
• Severe storm Dst -100 nT

(Gopalswamy et al., 2007)
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Causes of scatter

• Projection effects on speed
  (e.g., Burkepile et al., 2004)
• Fast/slow SW (Kahler 2004, not observed)
• CME width (Kahler et al., 1984, Gopalswamy et
  al., 2004)
• CME acceleration (e.g., Kocharov et al. 2001)
• Preceding CMEs (Gopalswamy et al. 2003)
• Preceding SEP events (Kahler 2001).

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References

• Cane et al. (2000), Geophys. Res. Lett., 27(21),
  3591, 10.1029/2000GL000111.
• Gopalswamy et al. (2004), J. Geophys. Res.,
  109(A12), A12105, 10.1029/2004JA010602.
• Gopalswamy et al. (2007), J. Geophys. Res., 112,
  A06112, doi10.1029/2006JA012149.
• Kahler et al. (1978), Sol. Phys., 57, 429.
• Srivastava et al. (2002), Geophys. Res. Lett.,
  29(9), 1287, 10.1029/2001GL013597.
• Valtonen (2006), Geophysical Monograph Series
  165, Gopalswamy, N., Mewaldt, R., and Torsti, J.
  (Eds.), AGU, Washington, DC, 21-32.
• Zhang et al. (2003), Astrophys. J., 582, 520.