1 Pedagogical Review on Solar Cycles King-Fai Li Caltech GPS, YL Yung Group Jan 17, 2007
2 Outline ► What are solar cycles? ► How are they related to climate? ► Our group ’ s efforts
3 What are solar cycles? ► First observed in the time series of sunspot number
4 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
5 MDI
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8 Babcock Model 27-day differential surface rotation
9 ► Total Spectral Irradiances Direct Observations ~0.1% change in the 11-yr solar cycle
10 Direct Observations ► F10.7 cm radio flux Blue: 90-day average
11 ► Lyman-a line (1215 Å) Direct Observations ~72% change in the 11-yr solar cycle
12 ► Mg-II core-to-wing index (2800 Å) ► Active and passive sunspot projected areas Direct Observations (More … )
13 How are they related to climate? Y L Yung ’ s Talk in CUHK, 2004
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16 How much is due to the solar cycle effect?
17 Empirical Data in Ozone Columns
18 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.
19 Our group ’ s 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.
20 Fraunhofer lines Measured on ground
21 Fraunhofer lines
22 Limb Spectra from Table Mountain 2005/6/ /9/23 OH absorption lines We have discovered some time-varying asymmetry between east and west limb Fraunhofer structures!
23 Summary ► What are solar cycles? ► How are they related to climate? ► Our group ’ s efforts To distinguish between natural variabilities and anthropogenic effects on climate To analysis the asymmetry between Fraunhofer structures at the solar limbs
24 References ► ► Babcock, H.W., The Topology of the Sun's Magnetic Field and the 22-YEAR Cycle, Astrophys. J., 133, , 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, ► ► Corti, S., F. Molteni, and T. N. Palmer, Signature of recent climate change in frequencies of natural atmospheric circulation regimes, Nature, 398(6730), , ► Pap, J. M., Periodicities of Solar Irradiance and Solar Activity Indices, I, Solar Physics, 129, ,1990. ► ► Rind, D., The Sun's Role in Climate Variations, Science, 296, 673 (2002).