Two modes of the differential rotation of the solar corona |
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| Authors: | O G Badalyan |
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| Institution: | (1) Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation, Russian Academy of Sciences, IZMIRAN, Troitsk, Moscow Region, 142190, Russia |
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| Abstract: | The differential rotation of the solar corona is studied using the brightness of the Fe XIV 530.3 nm green coronal line collected over 5.5 solar-activity cycles. The total observed velocity of the coronal rotation is analyzed as a superposition of two modes—fast and slow. A technique for separating two data series composing the initial data set and corresponding to the two differential-rotation modes of the solar corona is proposed. The first series is obtained by averaging the initial data set over six successive Carrington rotations; this series corresponds to long-lived, large-scale coronal regions. The second series is the difference between the initial data and the averaged series, and corresponds to relatively quickly varying coronal component. The coronal rotation derived from the first series coincides with the fast mode detected earlier using the initial data set; i.e., the synodic period of this mode is 27 days at the equator, then weakly increases with latitude, slightly exceeding 28 days at high latitudes. The second series describes a slow rotation displaying a synodic period of about 34 days. This coincides with the period of rotation of the high-latitude corona derived by M. Waldmeier for polar faculae. We expect that coronal objects corresponding to the fast mode are associated with magnetic fields on the scales typical for large activity complexes. The slow mode may be associated with weak fields on small scales. |
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