THE TOPOLOGY OF INTRASECTOR REVERSALS OF THE INTERPLANETARY MAGNETIC-FIELD

A technique has been developed recently to determine the polarities of interplanetary magnetic fields relative to their origins at the Sun b y comparing energetic electron flow directions with local magnetic fie ld directions. Here we use heat flux electrons from the Los Alamos Nat ional Laboratory (LANL) plasma detector on the ISEE 3 spacecraft to de termine the field polarities. We examine periods within well-defined m agnetic sectors when the field directions appear to be reversed from t he normal spiral direction of the sector. About half of these intrasec tor field reversals (IFRs) are cases in which the polarities match tho se of the surrounding sectors, indicating that those fields have been folded back toward the Sun. The more interesting cases are those with polarity reversals. We find no clear cases of isolated reverse polarit y fields, which suggests that islands of reverse polarity in the solar source dipole field probably do not exist. The IFRs with polarity rev ersals are strongly associated with periods of bidirectional electron flows, suggesting that those fields occur only in conjunction with clo sed fields. We propose that both those IFRs and the bidirectional flow s are signatures of coronal mass ejections (CMEs). In that case, many interplanetary CMEs are larger and more complex than previously though t, consisting of both open and closed field components.