Sector-structured interplanetary magnetic field associated with the fast plasma streams in 1985-1996

An analysis of 373 well-defined high-speed solar-wind streams observed at 1 AU during the years 1985 -1996 is outlined. The distribution of the occurr ence of these streams as a function of Bartels rotation days using the domi nant polarity of the interplanetary magnetic field (IMF) associated with th e referred fast streams shows that a four-sector pattern for the positive I MF polarity and a two-sector pattern for the negative IMF polarity are the dominant features in the investigated period. The high-speed streams seem t o occur at preferred Bartels days: positive polarity streams are most frequ ent near Bartels days 5 and 18, while negative polarity streams are most fr equent in days 14 and 23. Moreover, the corotating streams with positive IM F polarity prefer to occur in days 5 and 18 of the Bartels rotation period, whereas flare-generated streams with negative IMF polarity occur in days 1 4 and 23. The observed distribution of Bartels days is probably related to the distribution of the solar sources of high-speed solar wind streams as t he solar wind carries with it the photospheric magnetic polarity of the sol ar source region. In addition, the distribution of the streams reveals a si milar behaviour during the ascending and the declining phase of the last so lar cycle (22nd) in contrast to the previous one where it has an opposite a ppearance. Determined differences in the characteristics of the sector stru ctured IMF associated with the fast streams of the last cycle with the prev ious one (21st) and some similarities with the alternate solar cycle (20th) seem to be attributed to the 22-year magnetic cycle and to the polarity re versals of the polar magnetic field of the Sun. As the magnetic sectors are due to multiple crossings of the solar equatorial plane by a large-scale, warped heliospheric current sheet, it is suggested that the two-sector patt ern arises from a tilted solar magnetic dipole component and the more commo nly observed four-sector pattern from a quadrupole component of the solar i nterplanetary magnetic field.