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GEOEFFECTIVE INTERPLANETARY STRUCTURES: 1997 – 2001

SOLI INVICTO. GEOEFFECTIVE INTERPLANETARY STRUCTURES: 1997 – 2001. A. N. Zhukov 1,2 , V. Bothmer 3 , A. V. Dmitriev 2 , I. S. Veselovsky 2. 1 Royal Observatory of Belgium 2 Institute of Nuclear Physics, Moscow State University, Russia 3 Max–Planck–Institut für Sonnensystemforschung, Germany.

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GEOEFFECTIVE INTERPLANETARY STRUCTURES: 1997 – 2001

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  1. SOLI INVICTO GEOEFFECTIVE INTERPLANETARY STRUCTURES: 1997 – 2001 A. N. Zhukov1,2, V. Bothmer3, A. V. Dmitriev2, I. S. Veselovsky2 1Royal Observatory of Belgium 2Institute of Nuclear Physics, Moscow State University, Russia 3Max–Planck–Institut für Sonnensystemforschung, Germany

  2. General outline • An event: a day with Ap index more than 20 (one standard deviation interval during 1997 – 2000). • In total: 255 events in 1997 – 2000: in 1997 – 23; in 1998 – 41; in 1999 – 68; in 2000 – 74, in 2001 – 49. • Events are compiled into a database: http://alpha.sinp.msu.ru/apev • ACE and WIND spacecraft are used for the solar wind data. • I won’t talk about composition signatures, BDEs, etc. • This is an informal presentation of preliminary results. The investigations are not finished yet (to be published when the cycle ends).

  3. Coordinate system

  4. for 400 km/s ~135° IMF polarity

  5. IMF polarity for 400 km/s ~315°

  6. Geoeffective interplanetary structures ICME = Interplanetary Coronal Mass Ejection MICME = Multiple ICME CH/CIR = Corotating Interaction Region/Croronal Hole ICME/CIR Slow wind

  7. Fast solar wind • High speed: 400 – 800 km/s • Low density: ~ 3 cm-3 • High temperature: ~ 105 K ~ 10 eV • Stationary for long times • Strong Alfvenic fluctuations By the way: 1 eV = 1.6 104 K

  8. Slow solar wind • Low speed: 250 – 400 km/s • High density: ~ 10 cm-3 • Low temperature: ~ 104 K ~ 1 eV • Very variable By the way: 1 eV = 1.6 104 K

  9. Scheme of a CIR

  10. Event 26: CIR/CH

  11. Event 26: CIR/CH

  12. Event 26: CIR/CH

  13. IP shocks

  14. CIR shocks A typical CIR: with a forward/reverse shock pair (Lazarus et al. 1999)

  15. CME-driven interplanetary shocks Gold was right: interplanetary shocks (except CIR shocks) are CME-driven! (Courtesy R. Schwenn)

  16. CME-driven shocks have larger angular extent than CMEs themselves

  17. ICME • Shock (if the ICME is fast enough) • …followed by shocked sheath plasma (compressed and heated, with oscillating B) • …followed often by the driver gas (ICME itself): Low Strong magnetic field Temperature depression: typically < ~ 105 K ~ 10 eV Low variance of the magnetic field Large-scale smooth field rotation (magnetic cloud): in about 30% of cases Usually only a subset of these signatures is observed.

  18. ICME

  19. ICME

  20. ICME

  21. ICME

  22. ICME

  23. ICME

  24. ICME/CIR

  25. ICME/CIR

  26. ICME/CIR

  27. MICME

  28. MICME

  29. MICME

  30. Slow wind

  31. 1997 – 2001

  32. 1997 – 2001 During the whole studied period storms associated with ICMEs dominate (44%). However, in 1998 the fraction of storms produced by CIR/CH (41%) is comparable with the one of ICMEs (31%), and in 1999 it even becomes dominant (51%).

  33. 1997 – 2001 Although the fraction of storms produced by ICMEs has its minimum in 1999 (22%), the number of geoeffective ICMEs remains more or less the same in 1997 (9 separate ICMEs, 13 in total), 1998 (11 separate ICMEs, 19 in total) and 1999 (10 separate ICMEs, 19 in total). Therefore, the activity in 1999 is only very slightly anomalous.

  34. 1997 – 2001 The number of geoeffective ICMEs increased essentially during high activity years (2000 – 2001), as expected. The number of fast flows (CIR/CH) has its maximum during the rising phase of the cycle (1999). The number of storms caused by slow solar wind flows remains rather constant during the cycle.

  35. Geoeffective ICMEs • Almost half of geoeffective IMCEs are magnetic clouds (MC). • MCs of left-handed chirality slightly dominate.

  36. Geoeffective ICMEs In 1997 right-handed clouds are strongly predominant, in 1998 – 2000 the number of left-handed and right-handed clouds is almost the same and in 2001 (after the activity maximum and the reversal of the solar magnetic field!) left-handed MCs became strongly predominant. The relative fraction of MCs in respect to all ICMEs drops with the increase of solar activity.

  37. Geoeffective MCs MCs with both high and low inclination to the ecliptic are present.

  38. Ap index

  39. Ap index Storms produced by MICME and ICME/CIR have larger average Ap index. This could be due to two reasons: larger peak ap (interaction provides favorable conditions for producing stronger storms?) and/or longer duration of ap increase (natural if there are two or more structures).

  40. Peak ap (Kp) index

  41. Peak ap (Kp) index

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