EAST-WEST INCLINATION OF LARGE-SCALE PHOTOSPHERIC MAGNETIC-FIELDS

Sixteen years of WSO magnetogram data have been studied to determine t he solar cycle variation and latitude dependence of the east-west incl ination of photospheric magnetic field lines. East-west inclination is here defined as the angle between a field line and its local radial v ector, 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 polarit y and to change with the solar cycle. Leading and following polarities are tipped towards each by about 9 degrees and have an overall net ti lt in the direction of rotation (to the west) of 0.6 degrees. New cycl es are seen to begin at high latitudes and to grow through the lower l atitudes over approximately 5 years, providing evidence for an extende d cycle length of 16-18 years.