The role of CMEs in the solar cycle and Evidence for a Floor in the Open Magnetic Flux

1. The role of CMEs in the solar cycle and Evidence for a Floor in the Open Magnetic Flux Nathan Schwadron, N. Crooker, M. J. Owens, C. W. Smith, D. E. Connick, T. S. Horbury, O. C. St Cyr, N. Gopalswamy, S. Yashiro, H. Xie

2. The Helisphere’s Hale Cycle N- S+ N+ S- N- S+ N- S+ N+ S-

3. Evolving Magnetic Flux N+ S- N- S+ N+ S- Roughly factor x2 variation in Open Magnetic Flux N- S+ N+ S- N+ S- Wang et al., 2000

4. The Role of CMEs CMEs move flux via interchange reconnection CMEs temporarily add closed magnetic flux, increasing |B|, particularly during solar max

5. Temporary Flux Addition by CMEs Black line shows the observed value of |B| at 1 AU from ACE/Wind Red line shows simulated value of |B| at 1 AU using LASCO observed CME rates CME half-life 50 days Model comparison validates open flux conservation during CME ejections

6. CMEs and the Hale Cycle • CMEs generally have an orientation in agreement in with Hale’s law (Bothmer and Schwenn, Ann. Geophys., 1998) • Is the flux opened by Interchange Reconnection sufficient for field reversal? • Fopen = Open Flux ~1015 Wb • FCME=CME flux ~1012 Wb • freq = CME frequency ~ 3/day • d = CME footpoint separation • Number of Needed CMEs, • N =(Fopen/FCME)x(180o/d) • Time required for field reversal, • T = N/freq ≈ 11 years • Solve for footpoint separation • d > 5o

7. Owens et al., 2006

8. Cohen et al, 2009 – See Poster

9. CME rate – field correlation Owens et al., 2008

10. CME-rate |B| correlation Owens et al., 2008

11. Model of CME-|B| Correlation • |B| Floor of ~ 4 +/- 0.3 nT • Δ|B|min~ 0.5 nT (change from this to last min) • Accounted for by model if • Ejected CME flux of 1-2 x 1013 Wb • IC Reconnection time of ~30-50 days • Lowers the needed to footpoint separation to > 1 deg Owens et al., 2008

12. The Observed Toroidal Ejection Rates • Limits on the flux ejected by CMEs • Lower limit of 1x1023 Mx/yr (3x1012 Wb/dy) from Schwadron et al., 2008 based on open flux increase near max • Upper limit of 5.5x1023 Mx/yr (16x1012 Wb/dy) from Connick et al. based toroidal ejection rate • Owens et al. 2008 finds 1-2x1013 Wb ejected at a rate of 0.5/day => 5-10x1012 Wb/dy Connick, Smith, Schwadron 2008 (See Poster)

13. Interchange Reconnection: Mass and Energy Supply • Reconnection leads to 2 beams • Loop beam empties loop material into solar wind at Aflven speed • SW beam leads to incoming rain from the solar wind • Some electron heating SW beam Exhaust t2 Loop beam va opening loop t1 va va x t0

14. Flux-Flux Scaling Injected Elec.Mag. Energy/Particle Constant injected energy/particle implies injected power proportional to particle flux and magnetic flux: Injected Power proportional to magnetic flux

15. Solar Wind Power and Mass Flux Decreases with Time

16. Long-Term Evolution • Evidence of Open Flux Conservation over Large Timescales (Svalgaard and Cliver, 2007)

17. http://cor1.gsfc.nasa.gov >400 CMEs SOHO LASCO CME Rate in 1996-1997 was ~0.5 CMEs/day Preliminary CME Catalogue St. Cyr (Jan-Aug 2007) Hong Xie (Sep 2007-Sep2008) St. Cyr & Xie (Oct 2008-Jun2009)

18. SOHO LASCO CME Rate

19. CMEs and the Solar Cycle • Clear Correlation between Open Field Flux and CME rate • Clear evidence for Interchange Reconnection • IR with CMEs should help achieve the reversal • Recent observations suggest consistent limits on flux ejection by CMEs • The observed ejection rates easily support reversal over the 11 year solar cycle • We are now in a prolonged depression in open field strength, ejection rate, solar wind mass flux and solar wind power • These are all likely regulated through interchange reconnection with CMEs