Development of an active solar region August 20-26, 1954.

Abstract

view Abstract Citations References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Development of an active solar region August 20-26, 1954. Dodson, Helen W. Abstract It is possible to study the development of active solar regions under circumstances of unusual simplicity during the time when the sun is just emerging from minimum in the eleven-year cycle. The week of August 20-26, 1954 provided exactly this opportunity. Between 15h00m and 15h10m UT on August 20, a small calcium plage formed very close to the central meridian at about 300 south latitude. By 18h00m a spot was visible. In the week following its formation, the calcium plage grew to at least 3000 millionths of the solar hemisphere and became 2.4 times as bright as the dark portions of the mottled background of the K232 spectroheliograms. Isophotometric studies of the calcium plage as photographed at the McMathHulbert Observatory provide quantitative data for comparison with spot, magnetic, radio flux, and coronal data most kindly made available by astronomers in all parts of the world. At least four flares were observed in the region before it traversed the west limb. No other active regions were observed on the solar disk between August 20 and 25. To the best of our information, ionospheric disturbances did not accompany the observed flares. It is tempting to associate the recrudescence of geomagnetic activity in early September with the resurgence of observed solar activity in August, though the time relationships here indicated are far from those generally considered acceptable in such matters. The difficulties encountered in this study of a very simple case of solar activity give some indication of the problems that will be inherent in efforts to disentangle the complex solar data during the International Geophysical Year in 1957-58 when the sun will have advanced toward maximum in the eleven-year cycle of activity. AIcMath-Hulbert Observatory, University of Michigan, Ann Arbor, Mich. Publication: The Astronomical Journal Pub Date: February 1956 DOI: 10.1086/107267 Bibcode: 1956AJ.....61....2D full text sources ADS |