Preferred solar longitudes with signatures in the solar wind

Using spacecraft data collected over three solar cycles, Neugebauer et al. [2000] found a persistent dependence of the solar wind speed and the radial component of the interplanetary magnetic field on solar longitude, defined in a coordinate system with a rotation period of 27.03 days. Here we inves tigate the solar source of this period using observations of the photospher ic magnetic field. We study the lowest-order nonaxisymmetric modes of the s olar field extracted from synoptic charts of the Wilcox Solar Observatory. We find there is a robust magnetic structure on the Sun, which rotates with the period found by Neugebauer et al. [2000] in the solar wind. This rotat ion is more rapid than the solar equatorial and core rotations. We discuss the association of this nonaxisymmetric mode with the magnetic field genera ted by the solar mean field dynamo.