A Method to Determine the Solar Synodic Rotation Rate and the Height of Tracers |
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| Authors: | Ro?a D Vr?nak B Bo?i? H Braj?a R Ru?djak V Schroll A Wöhl H |
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| Institution: | (1) Astronomical Observatory, Croatian Natural Science Society, HR-10000 Zagreb, Croatia;(2) Faculty of Geodesy, University of Zagreb, Hvar Observatory, HR-10000 Zagreb, Croatia;(3) Sonnenobservatorium Kanzelhöhe, Universität Graz, A-9521 Treffen, Austria;(4) Kiepenheuer-Institut für Sonnenphysik, D-79104 Freiburg, Germany |
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| Abstract: | The dependence of the measured apparent synodic solar rotation rate on the height of the chosen tracer is studied. A significant error occurs if the rotation rate is determined by tracing the apparent position of an object above the photospheric level projected on the solar disc. The centre-to-limb variation of this error can be used to determine simultaneously the height of the object and the true synodic rotation rate. The apparent (projected) heliographic coordinates are presented as a function of the height of the traced object and the coordinates of its  footpoint . The relations obtained provide an explicit expression for the apparent rotation rate as a function of the observed heliographic coordinates of the tracer, enabling an analytic least-squares fit expression to determine simultaneously the real synodic rotation rate and the height of the tracer. |
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