Solar Wind: Dynamics and Effects on Earth's Activity

1. Solar wind Katya Georgieva Boian Kirov Simeon Asenovski

2. Solar wind – expansion of the solar corona • The solar corona is not in hydrostatic equilibruim • The corona ( the solar atmosphere) is expanding until it encounters the interstellar matter Eugene Parker (1956) The solar wind carries plasma with embedded magnetic fields to the EarthThe interaction of the solar wind with the Earth’s magnetic field leads to geomagnetic disturbances

3. 3 types of solar wind Slow solar wind:max in sunspot min • background geomagnetic activity • galactic cosmic rays modulation • solar wind electric field High speed solar wind: max during sunspot declining phase • recurrent geomagnetic storms • galactic cosmic rays modulation • energetic particles precipitation • solar wind electric field Coronal mass ejections: max during sunspot max • Sporadic geomagnetic storms • galactic cosmic rays modulation • energetic particles precipitation, solar proton events • solar wind electric field

4. 3 components of geomagnetic activity corresponding to the 3 types of solar wind • Floor – background geomagnetic activity due to the slow solar wind • Sunspot-related geomagnetic activity due to CMEs proportional in number and intensity to the sunspot number • Additional geomagnetic activity due to high-speed solar wind

5. Different relative importance of the 3 components of geomagnetic activity in different periods low “floor” of geomagnetic high “floor” of geomagnetic activity activity well expressed dependence of small to vanishing dependence geomagnetic activity on geomagnetic activity on sunspot-related solar activity sunspot –related solar activity small impact of non sunspot- high impact of non sunspot- related solar activityrelated solar activity

6. The time the Earth spends in slow solar wind from the equatorial streamer belt depends on thesolar cycle phase

7. Distribution of slow and fast solar wind • In sunspot min: slow solar wind confined to the ecliptic, fast wind at higher latitudes • In sunspot max slow and fast streams at all latitudes • Cycle to cycle variations

8. Variations of the thickness of the heliospheric current sheet The thicker the sheet (bigger gamma) – the higher the geomagnetic activity “floor”

9. Are solar wind parameters also changing from cycle to cycle? • We look at sunspot min periods • Divide the days into 4 groups: • - slow background solar wind (V<450 km/s) • - faster background solar wind (V>450 km/s) • - coronal mass ejections • - high speed solar wind

10. % of time during sunspot min

11. Variations from min to min – slow wind

12. Variations from min to min – fast wind

13. What is fast solar wind

14. By variations

15. Solar polarity changes from cycle to cycle

16. Solar rotation axis tilted by 7o

17. Seasonal variations of IMF direction

18. By variations in positive and negative polarity cycles

19. NAM and SAM indices

20. NAM index in positive and negative polarity cycles

21. SAM index in positive and negative polarity cycles