Abstract
Sixteen years of WSO magnetogram data have been studied to determine the solar cycle variation and latitude dependence of the east-west inclination of photospheric magnetic field lines. East-west inclination is here defined as the angle between a field line and its local radial vector, as projected onto the plane of the latitude and line of sight. Inclination is determined by a least-squares fit of observed magnetic fields to a simple projection model, and is found to depend on polarity and to change with the solar cycle. Leading and following polarities are tipped towards each by about 9° and have an overall net tilt in the direction of rotation (to the west) of 0.6°. New cycles are seen to begin at high latitudes and to grow through the lower latitudes over approximately 5 years, providing evidence for an extended cycle length of 16–18 years.
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Shrauner, J.A., Scherrer, P.H. East-west inclination of large-scale photospheric magnetic fields. Sol Phys 153, 131–141 (1994). https://doi.org/10.1007/BF00712496
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DOI: https://doi.org/10.1007/BF00712496