DELAY TIMES BETWEEN GEOEFFECTIVE SOLAR DISTURBANCES AND GEOMAGNETIC INDICES

1. DELAY TIMES BETWEEN GEOEFFECTIVE SOLAR DISTURBANCES AND GEOMAGNETIC INDICES Y. D. PARK1, Y. -J. MOON1, I. S. KIM2, H. S. YUN3 1.Korea Astronomy Observatory, Daejeon, KOREA 2. Sternberg State Astronomical Institute, Moscow Univ. RUSSIA 3. Seoul National Univ. Seoul, KOREA

2. I. INTRODUCTION • Geomagnetic Activities are associated with Solar Active Features(DSF, CME, Flares….) • Solar activity - Geomagnetic activities research : Gosling et al.( 1991), Gosling(1997), Hudson et al.(1998), Zarro et al.(1999), Sterning et al.(2000), Gilbert et al.(2000)….. • Primary mechanisms are not fully understood • Gosling suggestion (1993 “Solar Flare Myth”) : geomagnetic activities by fast CMEs are not necessarily associated with solar flares.

3. Delay times of solar disturbances • Several cases using simple correlation tools (e.g., Joselyn and McIn-tosh, 1981; ; Wright, 1983a; 1983b; Mikhailusta and Gnevyshev, 1985;Watanabe and Schwenn, 1989). • Joselyn and McIntosh(1981) : flare- geomagnetic storm relation 3 years data. • Wright(1983a, 1983b) disappearing prominences and Ap index.

4. Quantitative characteristics of delay times of geoeffective solar disturbances, using data taken for several decades. • Cross-correlation measure of point series data most probable delay time • Estimate the most probable time for major X-ray flares and disappearing filaments to travel from the Sun to the Earth. • Investigate delay time between SSC(storm sudden commencement)s and major geomagnetic storms. • Examined the dependence of correlation on the characteristics of solar disturbances such as their strengths, durations and locations.

5. II. DATA • NGDC – more than 2 solar cycle • 4836 solar X-ray flares stronger than M1 class recorded from Sep. 1, 1975 to Dec. 31,1999 • 1651 disappearing filaments occurred from Jan. 1, 1992 to Dec. 31, 1999 • 793 SSCs recorded from Sep. 1, 1975 to Dec. 31, 1999, • 408 major geomagnetic storms from Sep.1, 1975 to Dec. 31, 1999.

6. III. RESULT and DISCUSSION • Examined relationships solar flares - disappearing filaments, - SSCs. • X-ray flares duration –SSC

7. X-ray flares strength –SSC Flare duration should be a more significant factor than strength

8. traveling time of flare disturbance on heliolongitude

9. The cross-correlation between DSFs and SSC

10. Cross-correlation : DSFs of heliolongitudes - SSCs.

11. Cross-correlation : SSCs - starting time of major geomagnetic storms

12. Cross-correlation : SSCs - starting time of major geomagnetic storms • High correlation appearing at zero time lag  SSCs are a good sign of initiation of major geomagnetic storms. • Positive correlation  most of geomagnetic storms take place in about one and half days after SSCs occur.

13. VI. SUMMARY and CONCLUSION • The most probable traveling time of a solar disturbance from the Sun to the Earth is estimated to be about 2 days for solar major (X and M class) flares and about 3 days for disappearing filaments. • Long-duration flares are better correlated with SSCs than short duration flares are. This is consistent with that long-duration flares are frequently associated with CMEs and coronal and/or interplanetary shocks. • The traveling times of solar disturbances strongly depend on the heliolongitude where they originate. The disturbances associated with flares and laments located at the middle west longitude are approximately two times faster than those associated with flares located at the middle east longitude. • We have confirmed that solar disturbances associated with flares and disappearing laments at the western limb can hardly reach the Earth. Finally, our results are expected to be used as quantitative input parameters for predicting solar-terrestrial effects(e.g., Lundstedt, 1992).

14. The traveling times of solar disturbances strongly depend on the heliolongitude where they originate. The disturbances associated with flares and laments located at the middle west longitude are approximately two times faster than those associated with flares located at the middle east longitude. • We have confirmed that solar disturbances associated with flares and disappearing laments at the western limb can hardly reach the Earth. Finally, our results are expected to be used as quantitative input parameters for predicting solar-terrestrial effects(e.g., Lundstedt, 1992).