The rotation of calcium plages in the years 1967–1970 |
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| Authors: | Maurizio Ternullo |
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| Institution: | (1) Osservatorio Astrofisico di Catania, CNR-Gruppo Nazionale di Astronomia, U.d.R. di Catania, Citta' Universitaria, v. le A. Doria, I-95125 Catania, Italy |
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| Abstract: | An analysis of Ca II spectroheliograms obtained at Catania Observatory in the period 1967–1970 shows that plages rotate - in their first four days of lifetime - with a latitudinal differential rotation profile steeper than for older objects.A closer inspection reveals that plages slow down with age in some latitude strips, and accelerate in some others. That makes the profiles of old and young objects highly different from each other. In particular, the empirical laws of solar rotation usually adopted, appear to be inadequate to describe so complex a phenomenon as the rotation of these magnetic features. A close correspondence has been found between the latitudes at which plages accelerate (slow down) and the latitudes of westward (eastward) streams (Howard and LaBonte, 1980).Some implications of these results, in the light of the theory of a direct coupling of magnetic features to deep layers, are discussed.In the years concerned, Ca-plages of whatever age show differential rotation profiles steeper than in other phases of the solar cycle. |
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