ORIGIN OF THE SLOW SOLAR WIND

1. ORIGIN OF THE SLOW SOLAR WIND K. Fujiki，T. Ohmi, M. Kojima, M. Tokumaru Solar-Terrestrial Environment Laboratory, Nagoya University and K. Hakamada Department of Engineering Physics, Chubu University

2. Slow solar wind from a small equatorial coronal hole Slow solar wind from a polar coronal hole 2000 1991

3. Relation between speed and coronal hole area The speed of the solar wind scales with the coronal hole area. [Nolte et al., 1976] Intermediate and slow streams originated not in smaller coronal holes at low latitudes and from open field regions just outside coronal hole boundaries. [Neugebauer et al., 1998]

4. Wang & Sheely model Magnetic field configuration smaller expansion high speed larger expansion low speed RADIAL DISTANCE

5. Slow SW from an equatorial small CH

6. slower solar wind Solar Wind Structure at Solar Minimum

7. Carrington Rotations 1899-1901 August 6 – October 17, 1995 The slower wind originates from the vicinity of active regions

8. Carrington Rotations 1895-1897 April 19 – July 10, 1995 The slower wind also originates from the vicinity of active regions

9. CR1897 fast wind slow wind from seCH HPS slow wind

10. CR1897 106K fast wind slow wind from seCH HPS slow wind

11. CR1897 fast wind slow wind from seCH HPS slow wind

12. Solar Wind in CR 1897 (June 12 – July 10, 1995) Parameter Slow (HPS) Slower (seCH) Fast (leCH) VP [km/s] 343±12 323±9673±14 NP [cm-3] 11.7±3.3 10.2±0.6 3.2±0.5 TP [105 K] 0.39±0.14 0.55±0.112.20±0.39 TO [106 K] 1.85±0.24 1.99±0.191.42±0.13 Nα/ NP 0.009±0.003 0.031±0.0080.039±0.004

13. Solar Wind in CR 1897 (June 12 – July 10, 1995) Parameter Slow (HPS) Slow (seCH) Fast (leCH) VP [km/s] 343±12 323±9673±14 NP [cm-3] 11.7±3.3 10.2±0.6 3.2±0.5 TP [105 K] 0.39±0.14 0.55±0.112.20±0.39 TO [106 K] 1.85±0.24 1.99±0.191.42±0.13 Nα/ NP 0.009±0.003 0.031±0.0080.039±0.004

14. slow wind (SCH) coronal hole steady large

15. Slow SW from a polar CH

16. Polar Low-speed Solar Wind at Solar Activity Maximum of Cycle 22 June 27, 1990 Ohmi et al. [2001]

17. Polar Low-speed Solar Wind at Solar Activity Maximum of Cycle 23 October 23, 1999 Ohmi et al. [2002]

18. Small Polar Coronal Hole

19. slow slower fast slower Conclusions In addition to the slow solar wind from helmet streamer, the slow solar wind originates from small coronal holes. Wang and Sheely model of inverse correlation between velocity and expansion factor seems to explain these slower solar winds.

20. Magnetic Field in the Coronal Holes Photospheric Condition is significantly different. Is it really possible to explain same acceleration mechanism?

21. Required • More in situ observations of the slow stream from small coronal holes. ･･･ is difficult to observe the polar wind. • Physical properties of density, acceleration profile, and temperature in corona of the slow streams. 　　　･･･can be observed by SOLAR-B.(EIS/XRT)

22. ~fin~