Solar cycle

In older stars the hydrogen is eventually consumed and the rate of fusion slows. At this stage, gravitational collapse again occurs, resulting in an increase in pressure and temperature until He fusion starts. The products of this reaction are mostly carbon and oxygen. 

When the He supply becomes depleted smaller stars may explode under gravitational collapse or follow other pathways. Stars that are larger than about 20 solar masses (i.e. about 20 times the mass of the Sun, where 1 solar mass is about 2 x 10 kg) can collapse in a relatively controlled fashion until core temperatures reach the order of 10 °C. At this point carbon and oxygen fusion begins. The products are now the elements close to silicon in the periodic table, known as the silicon peak elements. 

---

Willson, R. C. (1997). Total Solar Irradiance Trend During Solar Cycles 21 and 22. Science 277 1963-1965. 

Mitchell, J. M., Jr., Stockton, C. W., Meko, D. M., Evidence of a 22-Year Rhythm of Drought in the Western United States Related to the Hale Solar Cycle Since the 17th Century, In B. M. McCormac and T. S. Seliga, eds., Solar-Terrestrial Inferences on Weather and Climate, D. Reidel Pub. Co., Holland, 1979, 125-143. 

Burchuladze, A. A., Pagava, S. V., Povinect, P., Togonidze, G. I., Usacevt, S., Radiocarbon variations with the 11-year solar cycle durinq the last century. Nature, 287, 320-322 (1980). 

In the preceding discussion, we have calculated the attenuation factors for 10Be for three periods, 200, 7 x 103 and 10s years. Of these the 200 and 7000 year periods are well established and have been ascribed to solar cycle variations and earth s magnetic field excursions, respectively. For detailed calculations on the effect of these variations on the production rates of isotopes by cosmic rays reference is made to Castagnoli and Lal, 75.)... 

Callis, L. B., and M. Natarajan, The Antarctic Ozone Minimum Relationship to Odd Nitrogen, Odd Chlorine, the Final Warming, and the 11-Year Solar Cycle, J. Geophys. Res., 91, 10771-10796 (1986). 

Thus, long-term trends in ozone must be extracted from variability due to the solar cycle, which has an 11-year period associated with it, as well as the quasi-biennial cycle (QBO), which is an oscillation of zonal winds in the stratosphere around the equator and which has a 26-30 month cycle (e.g., see Kane et al.,... 

For example, Bjarnason et al. (1993) examined column 03 measurements made at Reykjavik from 1957 to 1990 using a Dobson spectrometer and applied a stratospheric model that included variations due to seasons, the solar cycle, the QBO, and a linear trend. The combination of the data and model showed a variation of 3.5 + 0.8% in column 03 over a solar cycle and 2.1 + 0.6% over a QBO, on top of a linear trend of decreasing 03. 

Similarly, Fig. 13.12 shows the percentage deviation in regionally averaged stratospheric ozone for North America, Europe, and the Far East after variations due to the solar cycle, seasonal variations, the QBO, and atmospheric nuclear tests were subtracted out. Negative deviations are consistently seen in recent years, suggesting a long-term trend on top of the natural variability (Stolarski et al., 1992). 

At Arosa, Switzerland, where there are records back to 1926 (the longest data record available), the trend in annual mean 03 has been determined to be —(2.3 + 0.6)% per decade. When contributions due to the solar cycle, temperature, and stratospheric aerosol concentrations are taken into account, the trend is —(1.9 0.6)% per decade. However, the total measured column 03 includes both stratospheric and a smaller tropospheric contribution, and the latter has been increasing (see Chapters 14 and 16). This would tend to mask part of a decrease in stratospheric 03. Applying an estimate of the increase in tropospheric ozone gives a trend in stratospheric 03 of - (3.0 + 0.6)% per decade at Arosa (Staehelin et al., 1998b). 

Hood, L. L., The Solar Cycle Variation of Total Ozone Dynamical Forcing in the Lower Stratosphere, J. Geophys. Res., 102, 1355-1370 (1997). 

Figure 14.54, for example, shows the annual average number of sunspots from 1880 to the present, which clearly shows this cycle (Cliver et al., 1998). Both the sunspot number and the aa geomagnetic index have been used as proxies for the solar cycle. For the relatively short time period covered by available instrumental temperature records, both the sunspot number and the aa geomagnetic index are correlated to surface temperature (e.g., see Cliver et al., 1998 and Wilson, 1998). 

FIGURE 14.55 Reconstructed total solar irradiance from f6f0 to f995 using an 11-year solar cycle plus a longer term component of variability (adapted from Lean et al., 1995a). 

Kelly, P. M., and T. M. L. Wigley, Solar Cycle Length, Greenhouse Forcing and Global Climate, Nature, 360, 328-330 (1992). 

Wilson, R. M., Evidence for Solar-Cycle Forcing and Secular Variation in the Armagh Observatory Temperature Record (1844-1992), / Geophys. Res., 103, 11159-11171 (1998). 

Considering the long-term component of the total ozone monthly series (1926-1998) at Arosa, the analysis points out both the principal solar cycle and the decreasing trend starting from 1970s (Figure 6). 

Houghton J.T. (2001b). The IPCC Report 2001. Proceedings of the First Solar and Space Weather Euroconference The Solar Cycle and Terrectrial Climate (Santa Cruz de Tenerife, September 25-29, 2000). ESA SP, Noordwijk, 463, pp. 255-259. 

Figure 2.3 Dust production and gas mass return rate by different stellar types in solar masses per year and kpc-2 in the galaxy at the solar cycle. Stars produce mainly silicate or carbon dust only in some cases is a different kind of dust material formed, probably iron or some iron alloy (peculiar dust). Many additional dust components with much smaller abundance are formed in most cases (Data from Tielens 1999 Zhukovska el al. 2008). Abbreviations of stellar types AGB = asymptotic giant branch stars of spectral types M, S, or C OB = massive stars of spectral types O and B on or close to the main sequence RGB = massive stars on the red giant branch LBV = luminous blue variables WCL = Wolf-Rayet stars from the lower temperature range Novae = mass ejecta from novae SN = mass ejecta from supemovae.

Essentially all of the energy for life originates in the form of electromagnetic radiation from the sun. In radiometric units the radiant flux density of solar irradiation (irradiance) perpendicularly incident on the earth s atmosphere—the solar constant — is about 1366 W m-2. The solar constant varies by up to 3.4% from the average due to the earth s elliptical orbit. The value given is for the mean distance between the earth and the sun (the earth is closest to the sun on January 3, at 1.471 x 10s km, and furthest away on July 4, at 1.521 x 108 km). There are additional variations in solar irradiation based on changes in solar activity, such as occur for sun spots, which lead to the 11-year solar cycle (Pap and Frolich, 1999). In Chapter 6 (Section 6.5) we will consider the solar constant in terms of the annual photosynthetic yield and in Chapter 7 (Section 7.1) in terms of the energy balance of a leaf. 

For reasons not yet understood, the solar cycle operated at a greatly reduced amplitude during that time. Evidence suggests it did not cease entirely, but the sunspot number—an index representing the total level of sunspot... 

Friis-Christensen, E., and K. Lassen. Length of the Solar Cycle An Indicator of Solar Activity Closely Associated with Qimate. Science 254 (1991) 698. 

Lassen, K., and Friis-Christensen, E. Variability of the solar cycle length during the past five centuries and the apparent association with terrestrial climate. Journal of Atmospheric and Terrestrial Physics 57, no. 8 (1995) 835. Pearce, Fred. Suimy Side Up. Aew Scientist 159, no. 2142 (1998). 

---