Observations of heliospheric planar and offset-planar magnetic structures

Planar magnetic structures are regions of solar wind plasma where the magne tic field orientation is constrained within a fixed plane for durations of several hours. Within these structures, magnetic field discontinuities are seen, with the discontinuity surfaces being almost co-planar. The results o f a survey of planar magnetic structures detected by the Ulysses spacecraft are presented. When searching for these events using minimum variance anal ysis, a large population was detected of magnetic field structures whose di rections described small circles in the spacecraft's field of view (as oppo sed to great circles described by "classic" planar magnetic structures). It is likely that these "small-circle" events represents Alfvenic structures. Variations in the nature of the structures at various heliographic latitud es and differing solar wind conditions are described. Implications of the r esults of the survey are discussed.