The mean photospheric magnetic field of the sun seen as a star has been compared with the interplanetary magnetic field observed with spacecraft near the earth. Each change in polarity of the mean solar field is followed about 4 89 days later by a change in polarity of the interplanetary field (sector boundary). The scaling of the field magnitude from sun to near earth is within a factor of two of the theoretical value, indicating that large areas on the sun have the same predominant polarity as that of the interplanetary sector pattern. An independent determination of the zero level of the solar magnetograph has yielded a value of 0.1 โข 0.05 G. An effect attributed to a delay of approximately one solar rotation between the appearance of a new photospheric magnetic feature and the resulting change in the interplanetary field is observed.
The magnetic field of the sun seen as a star has been measured with the Crimean tower telescope (Severny, 1955) using the parallel beam from the coelostat mounting falling on the magnetograph slit. This method gives the mean (averaged over all the elements of the image with the distribution of the brightness as a weighting function) longitudinal field strength (for the description of the mean solar field observations see Severny, 1969). This mean solar field observed in March through June 1968 has been compared with observations of the interplanetary magnetic field obtained with the Ames Research Center magnetometers on the spacecraft Explorers 33 and 35, for which C. P. Sonett is the Principal Investigator. The spacecraft magnetometer experiments have been described by Mihalov et al. (1968). A brief report on this comparison has been given by Wilcox et al. (1969). All these papers should be consulted for further details.
The top graph in Figure 1 shows a comparison of the observed mean solar field (dots) with the polarity of the interplanetary magnetic field. The polarity of the interplanetary field was determined using the method described by Wilcox and Colburn (1969). The interplanetary data were plotted on the graph of solar observations taking account of the transit time of solar wind plasma from sun to earth, as described later in this paper. It can be seen in Figure 1 that every time (with one small