Pedagogical Review on Solar Cycles

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Pedagogical Review on Solar Cycles

• King-Fai Li
• Caltech GPS, YL Yung Group
• Jan 17, 2007

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Outline

• What are solar cycles?
• How are they related to climate?
• Our groups efforts

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What are solar cycles?

• First observed in the time series of sunspot
  number

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Solar and Heliospheric Observatory (SOHO)

• Michelson Doppler Imager (MDI)
• Ni I 6768 Å solar absorption line from the
  photosphere.
• Extreme ultraviolet Imaging Telescope (EIT)
• 171, 195, 284, and 304 Å, corresponding to light
  produced by highly ionized Fe-XI/X, XII, XV, and
  He-II
• Corona emissions

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MDI
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Babcock Model
27-day differential surface rotation
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Direct Observations

• Total Spectral Irradiances

• 0.1 change in the 11-yr solar cycle

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Direct Observations

• F10.7 cm radio flux

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Direct Observations

• Lyman-a line (1215 Å)

• 72 change in the 11-yr solar cycle

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Direct Observations (More)

• Mg-II core-to-wing index (2800 Å)
• Active and passive sunspot projected areas

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How are they related to climate?
Y L Yungs Talk in CUHK, 2004
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How much is due to the solar cycle effect?
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Empirical Data in Ozone Columns
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Solar Cycles and Climate

• Corti et al. (1999) External perturbation
  changes only the occurrence frequency of the
  natural modes due to the non-linearity of the
  system.
• QBO and Annular Modes are two examples of natural
  modes.

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Our groups effort

• Solar cycle Northern/Southern Annular Modes
  interactions from NCEP Reanalysis data
• Solar cycle QBO interactions from THIN AIR
  model
• Solar cycles on atmospheric chemical species from
  observations over Table Mountain Caltech/JPL
  photochemical Model
• Variability of Fraunhofer structures in the
  spectra (3080 Å) observed over Table Mountain.

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Fraunhofer lines
Measured on ground
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Fraunhofer lines
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Limb Spectra from Table Mountain
2005/6/13
OH absorption lines
OH absorption lines
We have discovered some time-varying asymmetry
between east and west limb Fraunhofer
structures!
2005/9/23
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Summary

• What are solar cycles?
• How are they related to climate?
• Our groups efforts
• To distinguish between natural variabilities and
  anthropogenic effects on climate
• To analysis the asymmetry between Fraunhofer
  structures at the solar limbs

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References

• Babcock, H.W., The Topology of the Sun's Magnetic
  Field and the 22-YEAR Cycle, Astrophys. J., 133,
  572-587, 1961
• Camp, C. D., M. S. Roulston, and Y. L. Yung,
  Temporal and Spatial Patterns of the Interannual
  Variability of Total Ozone in the Tropics, J.
  Geophys. Res., 108(D20), 4643, 2003.
• Corti, S., F. Molteni, and T. N. Palmer,
  Signature of recent climate change in frequencies
  of natural atmospheric circulation regimes,
  Nature, 398(6730), 799-802, 1999.
• Pap, J. M., Periodicities of Solar Irradiance and
  Solar Activity Indices, I, Solar Physics, 129,
  165-189,1990.
• Rind, D., The Sun's Role in Climate Variations,
  Science, 296, 673 (2002).