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

Explore a comprehensive overview of over a century's worth of solar wind data and its implications for understanding solar activity and geomagnetic changes. Discover long-term solar wind reconstruction trends, the concept of a floor in the interplanetary magnetic field, and the potential effects of a Gleissberg Minimum. Delve into recent observations and emerging consensus surrounding solar wind magnetic field reconstruction. Learn about the evolving dynamics of solar wind speed and its impact on geomagnetic activity. Gain insights into the Earth's magnetosphere and potential implications of a decrease in Earth's dipole. Join the discussion on Cycle 24 and the possibility of a Gleissberg Minimum. Explore validation techniques, dynamo models, and precursor predictions in solar activity research.

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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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