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~130 Years of Solar Wind Data: The Floor and More

~130 Years of Solar Wind Data: The Floor and More. E.W. Cliver Space Vehicles Directorate Air Force Research Laboratory. AGU 27-30 May 2008. Outline. Long-term solar wind reconstruction: Emerging consensus Floor in the IMF: Then & Now Secular variation of solar wind speed

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~130 Years of Solar Wind Data: The Floor and More

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  1. ~130 Years of Solar Wind Data: The Floor and More E.W. Cliver Space Vehicles Directorate Air Force Research Laboratory AGU 27-30 May 2008

  2. Outline • Long-term solar wind reconstruction: • Emerging consensus • Floor in the IMF: Then & Now • Secular variation of solar wind speed • Entering a Gleissberg Minimum?

  3. 2 2 2005 1 3 4 1 5 Long-term Solar Wind Magnetic Field Reconstruction: Emerging Consensus

  4. (Svalgaard & Cliver, JGR, 110(12), 2005) The IDV index has the useful property of being highly correlated with B and independent of V

  5. 2 4 3 2 2005 1 3 5 4 2 1 5 Long-term Solar Wind Magnetic Field Reconstruction: Emerging Consensus (Exception: McCracken, 2007)

  6. Floor - Annual averages of B show evidence for a floor ~ 4.5 nT - The sharp drop from 1945-1950 in the McCracken time series does not appear in geomagnetic data - The low value in 1901 from RL&F is in error (APR, priv. comm.)

  7. M M M M M Floor in the Solar Wind Magnetic Field: Direct Observations (27-Day Averages)

  8. ~4.4 nT Floor in the Solar Wind Magnetic Field: Recent Direct Observations

  9. (Muscheler et al., 2005) (Caballero-Lopez et al., 2004) Floor in the Solar Wind Magnetic Field: Cosmogenic Nuclei / long-term

  10. SSW + HSS + CME º SSW + HSS * SSW B (nT) M 245 μT M 200 μT M 115 μT M ~250 μT (Fisk et al., 1999; Owens & Crooker, 2006) Year Interpretation of Floor: Baseline Open Magnetic Flux

  11. Svalgaard & Cliver, ApJ Lett. 661, L203, 2007 B(nT) = 0.27R½+ 4.6 For SSN = 0 Then: B Total (ecliptic)= 4.6 nT; B RADIAL (all latitudes) = 3.0 nT Now: B Total (ecliptic) ~ 4 nT; B RADIAL (all latitudes) ~ 2 nT

  12. Floor (Rouillard et al., 2007; Svalgaard & Cliver, 2007) ~15% increase in solar wind speed during the last ~120 years

  13. Plea for Help to Magnetospheric Physicists Open Question: Effect of ~10% decrease of Earth’s dipole since ~1850 on geomagnetic activity? - Siscoe et al. (2002)  Decrease in activity (ISM model & Hill M/I coupling models) - Glassmeier et al. (2004)  Weak/no effect (scaling relationships between magnetospheric parameters & M)

  14. A Coming Gleissberg Minimum? Cycle 24 may be smallest in ~100 years Test of Long-term Reconstructions, Precursor Prediction Technique, Dynamo Models, … 164.5 158.5 120.8 75? (Svalgaard, Cliver, & Kamide, 2005)

  15. Conclusions • Consensus long-term B & V / Validation of IDV • Floor in IMF in ecliptic Btot ~4 nT & Br ~ 2 nT(SSN = 0) • ~15% increase in solar wind V since 1872?

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