1. Katya Georgieva Boian Kirov Simeon Asenovski
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 Earth The 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
energetic particles precipitation
Coronal mass ejections: max during sunspot max
Sporadic geomagnetic storms
energetic particles precipitation, solar proton events

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 activity related solar activity

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