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Dynamics of the high speed streams during the last four solar minima

This study examines the characteristics and variations of high-speed streams (HSSs) during the four most recent solar minima, including their duration, maximum velocity, velocity gradient, and intensity. The study also explores the geomagnetic variability during solar minima and analyzes case studies to understand the relationship between solar wind velocity and geomagnetic response.

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Dynamics of the high speed streams during the last four solar minima

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  1. Dynamics of the high speed streams during the last four solar minima Georgeta Maris1) ,Ovidiu Maris2) 1) Institute of Geodynamics “Sabba S. Stefanescu” RO-020032, Bucharest, Romania(gmaris@geodin.ro) 2) Institute for Space Sciences RO-077125, Bucharest, Romania September 9, 2009 IHY-ISWI Meeting, Sibenik - Croatia, 7-13 Sep. 2009 1

  2. Outline • High Speed Streams (HSSs): • Definition; • Selection criterion; • Data bases; • Parameters; • Solar minimum phases of SCs 20-23: • Definition; • HSS statistics by their parameters (d, Vmax , DVmax , I); • Geomagnetic variability during solar minima: • Aa; Ap; • Regression line analysis; • Transfer of energy from SW to the terrestrial magnetosphere; • Case analysis • Preliminary conclusion IHY-ISWI Meeting, Sibenik - Croatia, 7-13 Sep. 2009

  3. HSS DEFINITION: „A large increase in the solar wind velocity lasting for several days (at least two days)”. • MAIN SELECTION CRITERIUM: V1  100 km/s lasting for two days, where: V1 – the difference between the smallest 3-hr velocity value for a given day (V0) and the largest 3-hr value the following day (V1). • HSS CATALOGUES: (1964 – 1996: SCs nos. 20 – 22) • Lindblad, B.A., Lundstedt, H., 1981, Sol. Phys. 74, 197-206; 1983, Sol. Phys. 88, 377-382; • Lindblad, B.A., Lundstedt, H., Larsson B., 1989, Sol. Phys. 120, 145-152; • Mavromichalaki, H., Vassilaki, A., Marmatsouri, E., 1988, Sol. Phys. 115, 345-365; • Mavromichalaki, H., Vassilaki, A., 1998, Sol. Phys. 183, 181-200; • (1996 – 2007; SC 23) • Maris, O., Maris G., 2007, unpublished yet; at: http://www.spaceweather.eu/, in Cap. “Data Catalogs for SW” or at: http://venus.nipne.ro/new1/HSS_Catalogue.html). IHY-ISWI Meeting, Sibenik - Croatia, 7-13 Sep. 2009

  4. HSS Parameters: SC Minima: W < 20 • HSS durationd (days); • HSS maximum velocityVmax (km/sec); • HSS velocity gradientVmax= Vmax – Vo; • HSS intensity (importance)I = Vmax× d •  of some parameter during time unit (month, BR, year) were calculated or the weighted values, e.g.: Ip=I/d September 9, 2009 IHY-ISWI Meeting, Sibenik - Croatia, 7-13 Sep. 2009 4

  5. Duration SC 22 SC 20 SC 21 SC 23 September 9, 2009 IHY-ISWI Meeting, Sibenik - Croatia, 7-13 Sep. 2009 5

  6. Vmax SC 20 SC 22 SC 23 SC 21 September 9, 2009 IHY-ISWI Meeting, Sibenik - Croatia, 7-13 Sep. 2009 6

  7. Vmax SC 20 SC 22 SC 23 SC 21 September 9, 2009 IHY-ISWI Meeting, Sibenik - Croatia, 7-13 Sep. 2009 7

  8. IHY-ISWI Meeting, Sibenik - Croatia, 7-13 Sep. 2009

  9. IHY-ISWI Meeting, Sibenik - Croatia, 7-13 Sep. 2009

  10. Results: • Recurrent HSSs have the main maxima during the second part of descendant phases (near the minimum); • The higher values of the HSSs intensity were calculated during last parts of SCs 20 & 23 • HSSs produced by eruptive phenomena present the classical 11-yr variation with some pulses of activity during the descendant phases; • The strange low values of the HSS intensity in maxima of SCs 21 & 22 in comparison with the ones in maxima of SCs 20 & 23 September 9, 2009 IHY-ISWI Meeting, Sibenik - Croatia, 7-13 Sep. 2009 10

  11. Geomagnetic variability during solar minima: • Aa; Ap – for whole cycles and minimum intervals; • Dst; Ap – for some cases • Regression line analysis • SW velocity is a good approximation of the SW energy  • r (V; Aa)  0.58 for each cycle the condition Bz southward is not always fulfilled. (Pirvutoiu, C. et al., 2009, AIP, 141-150); • r (V; Ap) : 0.270 ÷ 0.647 in minima September 9, 2009 IHY-ISWI Meeting, Sibenik - Croatia, 7-13 Sep. 2009 11

  12. IHY-ISWI Meeting, Sibenik - Croatia, 7-13 Sep. 2009

  13. IHY-ISWI Meeting, Sibenik - Croatia, 7-13 Sep. 2009

  14. Case analysis V and Dst variations during the CH_HSS of 6 June 2006 (upper panel); the correlation coefficient and regression line of V and Dst index (bottom panel). HSS was registered into a negative IMF sector (Bx southward) ; Bz was southward, too. IHY-ISWI Meeting, Sibenik - Croatia, 7-13 Sep. 2009

  15. Solar wind velocity (V) during the HSS of April 30, 2008 and the geomagnetic response measured by Dst index (the upper panel); the regression line (the left panel); Bx < 0 (southward), Bz > 0 (northward) 8/14/2009 IHY-ISWI Meeting, Sibenik - Croatia, 7-13 Sep. 2009 IAU JD 16, Rio de Janeiro, 12-14 Aug. 2009 15

  16. Solar wind velocity (V) during the HSS of January 31, 2008 and the geomagnetic response measured by Dst index (the upper panel); the regression line (the left panel); Bx > 0 (northward), Bz alternates, with a negative majority IHY-ISWI Meeting, Sibenik - Croatia, 7-13 Sep. 2009 16

  17. Solar wind velocity (V) during the HSS of March 25, 2008 and the geomagnetic response measured by Dst index (the upper panel); the regression line (the left panel); Bx > 0 (northward), Bz < 0 (southward) 17 IHY-ISWI Meeting, Sibenik - Croatia, 7-13 Sep. 2009

  18. Preliminary Conclusions • Durations of the last four solar minima (SCs 20-23) are quiet equal (the present minimum exceeded 42 months!); • HSS number per minimum is slowly growing but it remains  3/month; • No significant differences between odd and even SCs; • Minima after low Rmaxare more active in HSSs; • Solar Minima  Minimum phases are not quiet intervals but they are periods with significant activity in corona where more equatorial CHs could appear  more HSSs geo-effective. IHY-ISWI Meeting, Sibenik - Croatia, 7-13 Sep. 2009 18

  19. Thank You for Your Kind Attention ! IHY-ISWI Meeting, Sibenik - Croatia, 7-13 Sep. 2009

  20. IHY-ISWI Meeting, Sibenik - Croatia, 7-13 Sep. 2009

  21. IHY-ISWI Meeting, Sibenik - Croatia, 7-13 Sep. 2009

  22. Entrance of particles and reconnection between solar wind and magnetosphere The northward IMF reconnects with the terrestrial magnetic field behind the poles. The reconnected line is added to the day side and a corresponding flux tube is removed from the night side and transported down the tail. The reconnected dayside tube moves along the magnetopause boundary and replaces the flux tube that was lost down the tail. (Dungey model, Cerrato et al., 2008) IHY-ISWI Meeting, Sibenik - Croatia, 7-13 Sep. 2009

  23. The merged field lines split into two open field lines. Then, the solar wind drags the reconnected field lines from the dayside to the night-side, stretches the field lines, and stores the energy in the form of magnetic tension. This energy is released when the “open” magnetic field lines reconnect again to form closed field lines, which return toward the Earth. (Dangey model, Cerrato et al., 2008). IHY-ISWI Meeting, Sibenik - Croatia, 7-13 Sep. 2009

  24. The correlation coefficient between Aa and I_HSS (1964-2007, SC 20 – 23): r = 0,31 IHY-ISWI Meeting, Sibenik - Croatia, 7-13 Sep. 2009

  25. IHY-ISWI Meeting, Sibenik - Croatia, 7-13 Sep. 2009

  26. IHY-ISWI Meeting, Sibenik - Croatia, 7-13 Sep. 2009

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