A simple model is used to present a unified picture of the polarity pattern of the interplanetary magnetic field observed during the solar cycle. Emphasis in this paper is on the field near solar maximum. The heliographic latitude dependence of the dominant polarity of the interplanetary magnetic field is explained in terms of weak poloidal (dipolar) field sources in the sun's photosphere. Unlike the Babcock theory, the author hypothesizes that the dipolar field exists at equatorial latitudes (0-20~ too, (as well as in polar regions) and that the major source of the interplanetary magnetic field observed near the ecliptic plane is the dipolar field from equatorial latitudes. The polarity of the interplanetary field data taken in 1968 and in the first half of 1969 near solar maximum may possibly be explained in terms of a depression of the dipolar field boundary in space. The effect on the solar wind of the greater activity in the northern hemisphere of the sun that existed in 1968 and in the first half of 1969 is believed responsible for this hypothesized depression, especially near solar maximum, of the plane separating the + and --dipolar polarity below the solar equatorial plane in space. Predictions are made concerning the interplanetary field to be observed near the ecliptic plane in each portion of the next solar cycle.
Rosenberg and Coleman (1969) have found evidence from an analysis of measurements of the interplanetary magnetic field taken mostly from 1965 through 1967 that the dominant polarity of the field was inward (negative, toward the sun) at heliographic latitudes above the solar equatorial plane and outward (positive, away from the sun) at latitudes below this plane during that time. The measurements used were taken mostly in the rising portion of the present solar cycle (a period of usually low geomagnetic and solar activity compared with the 1962-1964 time interval) between _+ 7.3 ~ in solar heliographic latitudes as measured from the solar equatorial plane and between 0.7 and 1.5 AU (see also Rosenberg, 1970).
The observed hemisphere-dependent dominant polarity followed the direction (and 1/r z extrapolated magnitude by the Parker model ( 1958)) of the sun's dipolar field as measured by Babcock (1955) andLivingston (1966). That is to say, interplanetary magnetic field data taken in the ecliptic plane above the solar equatorial plane (in December to June, if near the earth in space) had a dominant negative polarity. Data taken below this plane (in June to December, if near the earth) had a dominant positive polarity. For near-earth interplanetary measurements the negative polarity dominance was greatest in September and the positive polarity dominance was greatest in March, the extreme points, โข 7.3 ~ of the sinusoid in heliographic latitude that the earth follows. Thus, the phase relationship between the time of year and the percentage of negative polarity recorded by magnetometers on spacecraft following the ecliptic plane was in accordance with this low activity poloidal model. The author theorizes the lines of force from areas containing a weak, widespread dipolar field of one