RUI: Large-Scale Patterns of Motion and Magnetic Fields on the Sun

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Abstract - Snodgrass The Principal Investigator and his students will carry out research to explore the relationship of the Sun's large-scale patterns of surface motion and magnetic field to the solar activity cycle. They will analyze solar magnetograph observations taken at the 46-meter Tower Telescope at Mount Wilson Observatory and also analyze the Carrington maps of Hydrogen-alpha neutral lines and coronal holes compiled by the National Oceanic and Atmospheric Administration. Both data sets span a time period covering most (1967-76) of cycle 20, all of cycles 21 and 22 (1976-86 and 1986-96, respectively) and will, by the end of the funding period, include the beginning of cycle 23. The investigation will include projects to study (1) the meridional motions of both the field structures and the atmospheric gases, (2) the torsional oscillations, both in the rotation of the photosphere and in the rotation of the magnetic fields, (3) the relationship between sizes of magnetic features and their differential rotation profiles, (4) the correlation of magnetograms with neutral-line and coronal hole maps, (5) the association between the large-scale field and the loci of active regions early in the cycle, (6) the Sun's magnetic dipole and quadrupole moments, determined by least-squares fits to the magnetograph data, (7) the rotation of the dipole moment as compared with the rotation rates of coexisting coronal holes, and (8) the association between polar field reversals and the time evolution of the large-scale field. The results of the research will provide answers to questions regarding the role in the Solar cycle played by the large-scale background field, the nature of coronal holes, and the mechanism behind the torsional oscillations. In addition, they will provide boundary conditions for both the internal motions and fields i nferred through helioseismology and for the theoretical studies of the Sun's internal dynamics. The results will also provide reasons for more detailed, but shorter term, measurements made at other observatories and from space. All data reduction and computer analyses will be carried out at the computing facilities at Lewis and Clark College.