Hostname: page-component-cd9895bd7-7cvxr Total loading time: 0 Render date: 2024-12-26T02:03:00.917Z Has data issue: false hasContentIssue false
  • English
  • Français

Long-term evolution of sunspot magnetic fields

Published online by Cambridge University Press:  26 August 2011

Matthew J. Penn  and
William Livingston
Matthew J. Penn
Affiliation:
National Solar Observatory†, 950 N Cherry Av, Tucson AZ 85718 email: mpenn@nso.edu
William Livingston
Affiliation:
National Solar Observatory†, 950 N Cherry Av, Tucson AZ 85718 email: mpenn@nso.edu
Rights & Permissions [Opens in a new window]

Abstract

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

Independent of the normal solar cycle, a decrease in the sunspot magnetic field strength has been observed using the Zeeman-split 1564.8nm Fe I spectral line at the NSO Kitt Peak McMath-Pierce telescope. Corresponding changes in sunspot brightness and the strength of molecular absorption lines were also seen. This trend was seen to continue in observations of the first sunspots of the new solar Cycle 24, and extrapolating a linear fit to this trend would lead to only half the number of spots in Cycle 24 compared to Cycle 23, and imply virtually no sunspots in Cycle 25.

We examined synoptic observations from the NSO Kitt Peak Vacuum Telescope and initially (with 4000 spots) found a change in sunspot brightness which roughly agreed with the infrared observations. A more detailed examination (with 13,000 spots) of both spot brightness and line-of-sight magnetic flux reveals that the relationship of the sunspot magnetic fields with spot brightness and size remain constant during the solar cycle. There are only small temporal variations in the spot brightness, size, and line-of-sight flux seen in this larger sample. Because of the apparent disagreement between the two data sets, we discuss how the infrared spectral line provides a uniquely direct measurement of the magnetic fields in sunspots.

Keywords

Solar CycleSunspotFeI1564.8 nm
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 6 , Symposium S273: The Physics of Sun and Star Spots , August 2010 , pp. 126 - 133
Copyright
Copyright © International Astronomical Union 2011

References

Howe, R., Christensen-Dalsgaard, J., Hill, F., Komm, R., Schou, J. & Thompson, M. J.Astrophys. J. Lett. 701, L87CrossRefGoogle Scholar
Liu, Y., Norton, A. A., & Scherrer, P. H. 2007, Solar Phys. 241, 185CrossRefGoogle Scholar
Maltby, P., Avrett, E. H., Carlsson, M., Kjeldseth-Moe, O., Kurucz, R. L., & Loeser, R. 1986, Astrophys. J. 306, 284CrossRefGoogle Scholar
Mathew, S. K., Martinez Pillet, V., Solanki, S. K., & Krivova, N. A. 2007, Astron. Astrophys 465, 291CrossRefGoogle Scholar
Moon, Y.-J., Kim, Y.-H., Park, Y.-D., Ichimoto, K., Sakurai, T., Chae, J., Cho, K. S., Bong, S., Suematsu, Y., Tsuneta, S., Katsukawa, Y., Shimojo, M., Shimizu, T., Shine, R. A., Tarbell, T. D., Title, A. M., Lites, B., Kubo, M., Nagata, S., & Yokoyama, T. 2007, Pub. Astron. Soc. Jap. 59, 625.CrossRefGoogle Scholar
Norton, A. A. & Gilman, P. A. 2004, Astrophys. J. 603, 348.CrossRefGoogle Scholar
Penn, M. J. & Livingston, W. 2006, Astrophys. J. Lett., 649, L45CrossRefGoogle Scholar
Penn, M. J. & MacDonald, R. K. D.. 2007, Astrophys. J. Lett., 662, L123CrossRefGoogle Scholar
Schad, T. A. & Penn, M. J. 2010, Solar Phys. 262, 19CrossRefGoogle Scholar
Watson, F. & Fletcher, L. 2010, IAU Symposium 273, these proceedingsGoogle Scholar
Wesolowski, M. J., Walton, S. R., & Chapman, G. A. 2008, Solar Phys. 248, 141.CrossRefGoogle Scholar