High resolution mapping of the magnetic field of the solar corona |
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| Authors: | Martin D Altschuler Randolph H Levine Michael Stix John Harvey |
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| Institution: | (1) High Altitude Observatory, National Center for Atmospheric Research, 80303 Boulder, Colo., USA;(2) Present address: Dept. of Computer Science, S.U.N.Y. at Buffalo, 4226 Ridge Lea Road, 14226 Amherst, N.Y., USA;(3) Center for Astrophysics, Harvard College Observatory and Smithsonian Astrophysical Observatory, 02138 Cambridge, Mass., USA;(4) Universitäts-Sternwarte, Göttingen, F.R.G.;(5) Kitt Peak National Observatory, 85726 Tucson, Ariz., USA |
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| Abstract: | High resolution KPNO magnetograph measurements of the line-of-sight component of the photospheric magnetic field over the entire dynamic range from 0 to 4000 gauss are used as the basic data for a new analysis of the photospheric and coronal magnetic field distributions. The daily magnetograph measurements collected over a solar rotation are averaged onto a 180 × 360 synoptic grid of equal-area elements. With the assumption that there are no electric currents above the photospheric level of measurement, a unique solution is determined for the global solar magnetic field. Because the solution is in terms of an expansion in spherical harmonics to principal index n = 90, the global photospheric magnetic energy distribution can be analyzed in terms of contributions of different scale-size and geometric pattern. This latter procedure is of value (1) in guiding solar dynamo theories, (2) in monitoring the persistence of the photospheric field pattern and its components, (3) in comparing synoptic magnetic data of different observatories, and (4) in estimating data quality. Different types of maps for the coronal magnetic field are constructed (1) to show the strong field at different resolutions, (2) to trace the field lines which open into interplanetary space and to locate their photospheric origins, and (3) to map in detail coronal regions above (specified) limited photospheric areas.The National Center for Atmospheric Research is sponsored by the National Science foundation.Kitt Peak National Observatory is operated by the Association of Universities for Research in Astronomy, Inc. Under contract with the National Science Foundation. |
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