The polarities and locations of interplanetary coronal mass ejections in large interplanetary magnetic sectors

We have surveyed the ISEE 3 electron heat flux data to determine the polarities of the interplanetary magnetic field for the period 1978–1982. Many intervals of bidirectional electron (BDE) heat fluxes, signatures of the closed fields of interplanetary coronal mass ejections (ICMEs), were distributed among the magnetic sectors, often carrying sector boundaries. Here we examine the distribution of BDE intervals within the longest lived sectors of the ISEE 3 period to determine where ICMEs occur relative to the heliospheric current sheet (HCS). The intrasector BDE intervals, with polarities matching those of the sectors, appear to be uniformly distributed within the sectors, indicating that those ICMEs are not closely confined to the HCS. We estimate the ratio of intrasector matching polarity BDE intervals to opposite polarity BDE intervals to be about 10. The small number and short duration of opposite polarity BDE intervals suggest that injections of opposite polarity coronal mass ejections into sectors are rare. We found a number of mixed polarity BDE intervals, containing both matching and opposite polarities. These mixed polarity BDE intervals occur a factor of 5 less often than the single polarity BDE intervals alone do but are statistically more than twice as long in duration. We discuss possible origins of mixed polarity BDE intervals.