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CME earthward direction as an important geoeffective parameter

CME earthward direction as an important geoeffective parameter. R.-S. Kim 1,2 , K.-S. Cho 2 , Y.-J. Moon 2 , Y. Yi 1 , Y.-D. Park 2 , Y. H. Kim 2 1 Chungnam national University 2 Korea Astronomy and Space science Institute. Contents. Review of the previous work

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CME earthward direction as an important geoeffective parameter

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  1. CME earthward direction as an important geoeffective parameter R.-S. Kim1,2, K.-S. Cho2, Y.-J. Moon2, Y. Yi1, Y.-D. Park2, Y. H. Kim2 1Chungnam national University 2Korea Astronomy and Space science Institute

  2. Contents • Review of the previous work • The earthward direction of a CME • Result • Conclusion

  3. 1200 800 400 Speed (Km/s) -60 -30 0 30 60 (East) (West) Longitude (degree) Forecast CME geoeffectiveness • Probability of CME geoeffectiveness • According to CME speed and location (Kim et al., 2005; JGR accepted) • Geoeffective CME: result in the geomagnetic storm (Dst ≤ -50 nT)

  4. Forecast CME geoeffectiveness • Forecast evaluation of CME geoeffectiveness • Predicted yes: for fast CME (≥ 800km/s), -30 ≤ Lon. ≤ +60 for slow CME (< 800km/s), 0 ≤ Lon. ≤ +30 • Observed yes: Dst < -50 nT • PODy: 0.65, PODn: 0.66, FAR: 0.45, Bias: 1.18, CSI: 0.42

  5. CME earthward direction • Direction and location

  6. a b CME earthward direction • Determination (Moon et al., 2005) • The SOHO/LASCO C2 running difference image. • Draw an ellipse on the front edge of a CME. • Connect the center of the ellipse and the solar disk center.

  7. a b CME earthward direction • Determination (Moon et al., 2005) • The ratio (b/a) between the shorter distance (b) and the longer distance (a) is the direction. • To the Earth: b/a ~ 1 To the side: b/a ~ 0 • It is directly estimated from coronagraph observation.

  8. Result I – direction and geoeffectiveness • Direction vs. |Dst| (293 CME-Dst pairs)

  9. Result I – direction and geoeffectiveness • Direction vs. |Dst| (V ≥ 800 km/s, 148 events)

  10. Result I – direction and geoeffectiveness • Direction vs. |Dst| (V < 800 km/s, 145 events)

  11. Result I – direction and geoeffectiveness • Geoeffectiveness of Direction

  12. Result II – forecast evaluation • Direction criterion

  13. Result II – forecast evaluation • 2002/07/15 21:30:05 • Speed: 1300 km/s • Location: N19W01 • Direction: 0.04 • Dst index: -13 nT

  14. Result II – forecast evaluation • 2001/10/20 02:26:05 • Speed: 764 km/s • Location: N14W35 • Direction: 0.76 • Dst index: -76 nT

  15. Result II – forecast evaluation • Direction criterion 0.70 0.15

  16. Result II – forecast evaluation • Contingency table based on the combination • Predicted yes: speed, location, direction • Observed yes: Dst < -50 nT • PODy: 0.70, PODn: 0.65, FAR: 0.44, Bias: 1.25, CSI: 0.45 (cf. PODy: 0.65, PODn: 0.66, FAR: 0.45, Bias: 1.18, CSI: 0.42)

  17. Conclusion • Earthward direction parameter • All CMEs associated with strong geomagnetic storms (Dst ≤ -200 nT) have large direction parameters (≥ 0.55). • The direction parameter is more important for fast CMEs (≥ 800 km/s) than for slow CMEs (< 800 km/s). • If direction of fast CME (V ≥ 800 km/s) is larger than 0.6, the probability of geoeffectiveness is 0.64. • Forecast evaluation • Determined by three parameters (speed, location, and direction) PODy: 0.70, PODn: 0.65, FAR: 0.44, CSI: 0.45, respectively. • The statistics are slightly improved.

  18. Further Work • Data consideration • Angular width vs. direction • Position angle vs. direction • Other parameters • ICME leading polarity : IPM Bz component …

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