Semiannual and solar‐cycle variation of sector structure

The complexity of the interplanetary magnetic‐field polarity pattern shows a semiannual variation, with more sectors per solar rotation in May and June, and again in November and December, times when the earth is close to the sun's equatorial plane. Complexity varies also through the solar activity cycle, in a manner consistent with contribution to the interplanetary field from both the polar field and long‐lived, large‐scale fields related to active regions.