Abstract
In this paper we investigate the changes that occur in measured magnetic fields when they are transformed into a heliographic coordinate system. To carry out this investigation we took measurements of the vector magnetic field of an active region that was observed at 1/3 the solar radius from disk center and transformed the observed field into heliographic coordinates. We also examined differences in the calculated potential field that occur when the heliographic normal component of the field is used as the boundary condition rather than the observed line-of-sight component. The results of this analysis show (1) that the observed fields of sunspots more closely resemble the generally accepted picture of the distribution of umbral fields if they are displayed in heliographic coordinates, (2) that the differences in the potential calculations are less than 200 G in field strength and 20° in field azimuth outside sunspots, and (3) that differences in the two potential calculations in the sunspot areas are no more than 400 G in field strength but range from 60 to 80° in field azimuth in localized umbral areas.
Similar content being viewed by others
References
Altschuler, M. D. and Newkirk, G. Jr.: 1969, Solar Phys. 9, 131.
Chapman, G. A. and Sheeley, N. R.: 1968, in K. O. Kiepenheuer (ed.), ‘Structure and Development of Solar Active Regions’, IAU Symp. 35, 161.
Giovanelli, R. G.: 1980, Solar Phys. 68, 49.
Giovanelli, R. G.: 1982, Solar Phys. 80, 21.
Hagyard, M. J., Cumings, N. P., West, E. A., and Smith, J. E.: 1982, Solar Phys. 80, 33.
Hagyard, M. J., Smith, J. B., Jr., Teuber, D., and West, E. A.: 1984, Solar Phys. 91, 115.
Hale, G. E. and Nicholson, S. B.: 1938, Publ. Carnegie Inst., No. 498.
Schmidt, H. U.: 1964, in W. N. Hess (ed.), Physics of Solar Flares, NASA SP-50, p. 107.
Teuber, D., Tandberg-Hanssen, E., and Hagyard, M. J.: 1977, Solar Phys. 53, 97.
Wellck, R. E. and Nakagawa, Y.: 1973, NCAR-TN/STR-87.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Hagyard, M.J. Changes in measured vector magnetic fields when transformed into heliographic coordinates. Sol Phys 107, 239–246 (1987). https://doi.org/10.1007/BF00152022
Received:
Issue Date:
DOI: https://doi.org/10.1007/BF00152022