1. Comparing the Large-Scale Magnetic Field During the Last Three Solar Cycles Todd Hoeksema

2. Evolution of the Large-Scale Magnetic Field Over Three Solar Cycles Global Properties Corona & Heliosphere Zonal Magnetic Field Toroidal Magnetic Field

3. Daily Solar Mean Magnetic Field – Sun as a Star 3 Cycles – 1975 - 2009 WSO Sensitivity Issues in ~2001 Rotation Modulation Observed At < 10 uT

4. 4 Solar Minima, 3 Polar Reversals 1976 - 2009 WSO Large-scale Polar Aperture 55 to Pole Surge Arrival South stronger In Cycles 21 + 22

5. MDI Measured Polar Field during Cycle 23 1996-2008 Movie shows observed and Interpolated polar field above 62 Smaller 75+ Polar Field Is More Symmetric & Reverses Later Difference in Strength is Significant, but Smaller

6. MDI Measured Polar Field during Cycle 23 1996-2008 Movie shows observed and Interpolated polar field above 62 Smaller 75+ Polar Field Is More Symmetric & Reverses Later Difference in Strength is Significant, but Smaller

7. Axial, Equatorial, and Total Solar Dipole – 3 Cycles 1976 - 2009 Total Axial Equatorial

8. Total Solar Dipole, Quadrupole, Octupole – 3 Cycles 1976 - 2009 Dipole Quadrupole l = 3 Magnitude @ 2.5Rs

9. Computed Source Surface Magnetic Field

10. The Computed Coronal Field & HCS During Cycle 23 1996-2009 Every 10 th Rotation Each panel 2 Rots wide Reversal in 1999-2000 Stable Structures Dipole and Quadrupole Dominate

11. 3 Cycles of the Computed HCS Inclination Best SS Radius may be 1.8 Rs this minimum – Sun & Hoeksema SH11A-1487

12. From McComas et al., GRL 2008 Ulysses Observed Different Solar Wind Structure During Solar Minimum in 1996 compared with 2008 Low-latitude is more complex and wider due to Decreased importance of Polar Coronal Holes Thanks to J. Luhmann Note: Coronal snapshot useful, but may mislead since structure reflects rotation

13. Ulysses also saw low IMF at high heliolatitudes in 2007 (Smith et al., GRL, 2008) –OMNI data from NSSDC Thanks to J. Luhmann IMF Measured at L1 is Significantly Weaker this Minimum than the Previous Three IMF observed to be uniform at all latitudes away from HCS

14. Thanks to J. Luhmann Computed open flux foot points – Coronal Hole Proxy Each Panel shows ~10 years starting 1972. Low latitude holes are relatively more important during this solar minimum 1973 1983 1993 2003

15. (GONG website movie, MSFC sunspot illustrations) The long decline of Solar Cycle 23 has been marked by very few, well separated Active Regions

16. Comparison of Large-Scale Corona in Cycles 21 & 23 Panels spaced By 12 rotations. CYCLE 23: Longer Fewer Contours Gradual Flattening Structures Persist More Dipole in Declining Phase Cycle 21Cycle 23

17. Comparison of Large-Scale Corona in Cycles 22 & 23 Panels spaced By 12 rotations. Cycle 23: Fewer Contours Slower Flattening Structures Persist Thanks to Weak Poles Both Dipolar During Reversal Cycle 22Cycle 23

18. Back to the Photospheric Field

19. Zonal Average of Total Flux and Net Flux – 3 Cycles 1976-2009 from WSO ~2001 WSO Sensitivity

20. Antisymmetric Zonal Symmetric Zonal Old Polarity Surge 2003/4

21. Toroidal (East-West) Field – 3 Cycles from WSO Cycles overlap several years and are extended Work with Leyan Lo & Phil Scherrer

22. From wattsupwiththat website Comparison of SSN for last 5 Cycles

23. From Wikipedia website Perspective Comes from Taking the Long View

24. Summary - 1 Cycle 23 was longer and weaker (relative to 21 and 22): MF, pole, meridional flow, corona, solar wind, dipole Polar Reversal on time, but no subsequent growth – no organized poleward migration Corona/Heliosphere not as constrained by dominant Polar Coronal Holes

25. Summary - 2 Corona/Heliosphere not constrained by dominant Polar Coronal Holes in declining phase of Cycle 23 HCS continued to reach high latitude Mid latitude structure in solar wind and low latitude coronal holes Very few spots in last few years.

26. Summary - 3 Zonal Flux Reduced Poleward flows small Antisymmetric flows at low latitude only 2002 not like 1991, 1981 Old polarity anti- symmetric flow in 2003 Interesting to learn what was ‘absent’ in 2003-2004 Toroidal flux pattern about the same New flux emerges just after previous max at high latitude and expands equatorward