Dynamics of the high speed streams during the last four solar minima
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Dynamics of the high speed streams during the last four solar minima. G eorgeta Maris 1) , O vidiu Maris 2) 1) Institute of Geodynamics “Sabba S. Stefanescu” RO-020032, Bucharest, Romania ([email protected]) 2 ) Institute for Space Sciences RO-077125, Bucharest, Romania.

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

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([email protected])

2) Institute for Space Sciences

RO-077125, Bucharest, Romania

September 9, 2009

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

1


Outline
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


  • 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  • Maris, O., Maris G., 2007, unpublished yet; at: http://www.spaceweather.eu/, in Cap.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


Hss parameters
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


    Duration

    SC 22

    SC 20

    SC 21

    SC 23

    September 9, 2009

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

    5


    Vmax

    SC 20

    SC 22

    SC 23

    SC 21

    September 9, 2009

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

    6


    V max
    Vmax

    SC 20

    SC 22

    SC 23

    SC 21

    September 9, 2009

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

    7




    • 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


    • 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




    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


    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


    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


    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


    Preliminary Conclusions 2008 and the geomagnetic response measured by Dst index (the upper panel); the regression line (the left panel);

    • 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


    Thank You for Your Kind Attention ! 2008 and the geomagnetic response measured by Dst index (the upper panel); the regression line (the left panel);

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


    IHY-ISWI Meeting, Sibenik - Croatia, 7-13 Sep. 2009 2008 and the geomagnetic response measured by Dst index (the upper panel); the regression line (the left panel);


    IHY-ISWI Meeting, Sibenik - Croatia, 7-13 Sep. 2009 2008 and the geomagnetic response measured by Dst index (the upper panel); the regression line (the left panel);


    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


    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


    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




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