K.R. Sivaraman and S.S. Gupta (Indian Institute of Astrophysics, Bangalore) spent about four months at NSO, beginning in mid-June 1998, working with Bob Howard on completing the analysis of the merged data set of the Sunspot position and area measures from the Kodaikanal and Mt. Wilson data sets for the years 1917-1985, and deriving the differential rotations for sunspot groups and individual spots. This combined data set forms the most accurate and complete set currently available for sunspot groups and certainly for individual spots. The analysis of the entire Kodaikanal sunspot measurements for 82 years (1906-1987) for differential rotation and its variation with sunspot cycle are in progress.
During this period, Sivaraman and Gupta also worked with Bill Livingston on looking for spatial correspondence of the chromospheric K-line inner network bright points and the arcsec inner network magnetic elements at the photospheric level with fresh data. These data consist of near temporally simultaneous spectroheliograms in the K 2v emission peak with a pass band of 40 mÅ obtained at the McMath-Pierce Telescope and magnetic scans at the spectro-magnetograph of the Vacuum Telescope on quiet regions at the center of the solar disk. The spectroheliograph setup was fabricated by Keith Pierce for this program. They find that 70% of these bright points correspond spatially to the inner network magnetic elements while the remaining 30% do not. This confirms the earlier findings of Sivaraman and Livingston (Sol. Phys., 1982, 80, p. 227).
K.R. Sivaraman, S.S. Gupta