The Second Annual Lowell Observatory Fall Workshop

The Solar Activity Cycle and Sun-As-A-Star Variability in the Visible and Infrared
Karen L. Harvey, Solar Physics Research Corporation

5. Summary

The material presented in this paper can be summarized as follows:

The total irradiance varies in phase with the solar cycle increasing from cycle minimum to maximum by 0.1%. A composite total irradiance record indicates that the two observed minima have the same level. The observed variations in total irradiance are the result of faculae, which increase the irradiance, and sunspots which decrease the irradiance.
The spectral irradiance has a variability that is significantly larger than the total irradiance. The variability on time scales of days is dominated by emerging regions and plage, on time scale of weeks by plage and enhanced network, and on time scales of months to years by the enhanced and quiet network. Summed over all activity structures, i.e. integrated over the disk, the spectral intensity-magnetic flux relation likely varies with the solar cycle.
Cycles persisted throughout the Maunder Minimum with lengths that appear to be around 11 years. Sunspots, however, were restricted to lower latitudes, that is within about 20° of the equator. There is also some suggestion that the rotation rate of sunspots was slower during the Maunder Minimum than is observed in sunspots over the last century.

Acknowledgments

This work was supported by NSF Grant ATM-9707010 and NASA Contract NAGW-4721. My appreciation to Drs. J. Lean and C. Fröhlich for making available the total irradiance and solar spectrum for this paper. The NSO/Kitt Peak data used here are produced cooperatively by NSF/NOAO, NASA/GSFC, and NOAA/SEC.

References

Brouwer, M. P. and Zwaan, C.: 1990, Solar Phys. 129, 220.

Castenmiller, M. J. M, Zwaan, C., and van der Zalm, E. B. J.: 1986, Solar Phys. 105, 237.

Chapman, G., Cookson, A. M., and Dobias, J. J. 1996, J. Geophys. Res. 101, 13, 541.

Fligge, M., Solanki S. K., Unruh, Y., Fröhlich, C., and Wehrli, Ch.: 1998, in K.S. Balasubramaniam, J.W. Harvey and D.M. Rabin (eds.), Synoptic Solar Physics, 18th NSO/Sacramento Peak Summer Workshop, ASP Conference Series, in press.

Foukal, P. 1981, in L.E. Cram and J.H. Thomas (eds.), `The Physics of Sunspots', Sacramento Peak Observatory Summer Workshop, pp. 391.

Fox, P. A., Fontenla, J. White, O. R., Harvey, K. L., and Avrett, E. H.: 1997, in preparation.

Fröhlich, C.: 1994, in J.M. Pap, C. Fröhlich, H.S. Hudson, R.C. Willson, (eds.), `The Sun as a Variable Star: Solar and Stellar Irradiance Variations', Cambridge Univ. Press, pp. 28.

Fröhlich, C. and Lean, J.: 1997, in F.L. Deubner (ed.), New Eyes to see inside the Sun and Stars, IAU Symposium 185, Kyoto, August 1997, Kluwer Academic Publ., Dordrecht, The Netherlands, in press.

Gaizauskas, V., Harvey, K. L., Harvey, J. W., and Zwaan, C.: 1983, Astrophys. J. 265, 1056.

Harvey, K. L. 1994, in J. Pap, C. Fröhlich, H.S. Hudson, S.K. Solanki (eds.), The Sun as a Variable Star: Solar and Stellar Irradiance Variations, IAU Coll. 143, Cambridge University Press, Great Britain, p. 217

Harvey, K. L and White, O. R. 1996, SPRC Technical Report 96-01.

Harvey, K. L and White, O. R. 1998, in K.S. Balasubramaniam, J.W. Harvey and D.M. Rabin (eds.), Synoptic Solar Physics, 18th NSO/Sacramento Peak Summer Workshop, ASP Conference Series, in press.

Harvey, K. L. and Zwaan, C.: 1993, Solar Phys. 148, 85.

Hoyt, D. V. and Schatten, K. H.: 1998, Solar Phys., in press.

Lean, J.: 1988, Adv. Space Res. 8, No. 7, 85.

Lean, J. and Fröhlich, C.: 1998, in K.S. Balasubramaniam, J.W. Harvey and D.M. Rabin (eds.), Synoptic Solar Physics, 18th NSO/Sacramento Peak Summer Workshop, ASP Conference Series, in press.

Lean, J. L., Cook, J., Marquette, W., and Johannesson, A.: 1998, Astrophys. J., in press.

Pap, J.: 1997, in Past and Present Variability of the Solar-Terrestrial System: Measurement, Data Analysis and Theoretical Models, Enrico Fermi Summer School, Varenna, Italy

Rabin, D., Wilson, R. M., and Moore, R. L.: 1986, Geophys. Res. Let. 13, 352.

Rabin, D., DeVore, C. R., Harvey, K. L.., and Hoeksema, J. T.: 1991, in A. N. Cox, W. C. Livingston, and M. S. Matthews (eds.) The Solar Interior and Atmosphere, Univ. of Arizona Press, pp. 781.

Ribes, J. C. and Nesme-Ribes, E.: 1993, Astron. Astrophys. 246, 549.

Skumanich, A., Lean, J. L., White, O. R., and Livingston, W. C.: 1984, Astrophys. J. 282, 776.

Solanki, S. K., and Unruh, Y. C.: 1998, Astron. Astrophys., in press

Steinegger, M., Brandt, P. N., and Haupt, H. F.: 1996, Astron. Astrophys, in press.

Worden, J., White, O. R., and Woods, T. N.: 1997, Astrophys. J., in press.

Zwaan, C.: 1996, Solar Phys. 169, 265.

[First | Prev | Discussion]
[Contents]