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Sunspot Motions from a Study of Kodaikanal and Mount Wilson Observations

  • Robert F. Howard (a1), K. R. Sivaraman (a2), S. S. Gupta (a2) and Pamela I. Gilman

Abstract

A study of the daily motions of individual sunspots and of sunspot groups has been undertaken using Kodaikanal and Mount Wilson white-light observations. The Mount Wilson measurements were completed several years ago, and the Kodaikanal measurements have recently been started, using a technique identical to that used for the Mount Wilson data. Both data sets started early in this century, and both have continued to the present time. Preliminary results of a comparison of the two data sets are presented which show a good agreement between them in spot areas and motions. Analysis of the combined data set for the years that are available so far indicates that many more spots are available in such a reduction because the 12-hour time difference between the two sites allows for a more certain identification of individual spots from one observation to the next than in the case when data from only one site are used. This greatly increases the number of sunspots available for motion studies, particularly the smaller sunspots. Preliminary rotation and latitude drift reduction from the combined data set confirm earlier results from the Mount Wilson data alone.

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Copyright

References

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Bogdan, T. J., Gilman, P. A., Lerche, I., and Howard, R.: 1988, Astrophys. J. 327, 451.
Gilman, P. A., and Howard, R.: 1984a, Astrophys. J. 283, 385.
Gilman, P. A., and Howard, R.: 1984b, Solar Phys. 93, 171.
Gilman, P. A., and Howard, R.: 1985, Astrophys. J. 295, 233.
Gilman, P. A., and Howard, R.: 1986, Astrophys. J. 303, 480.
Howard, R., Gilman, P. A., and Gilman, P. I.: 1984, Astrophys. J. 283, 373.
Howard, R., and Gilman, P. A.: 1986, Astrophys. J. 307, 389.
Schröter, E. H.: 1985, Solar Phys. 100, 141.
Wöhl, H.: 1988, Solar Phys. 116, 199.

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