ISEE 3 magnetic field and proton data are used to study the properties of rotational and tangential discontinuities in the solar wind. A Sonnerup‐Cahill minimum variance analysis of the magnetic field data is used to determine the direction of the normal to each discontinuity. The discontinuities are then classified as rotational (RD), tangential (TD), or either (ED), depending on the relative values of the normal field component and the change of field magnitude across them. This process yields substantially more RD's than TD's, in agreement with earlier studies using this method of classification. Other field and plasma parameters are then examined for each of these three groups. The field magnitude passes through a local minimum while the field direction is changing for some TD's but not for RD's. The first and second adiabatic invariants for protons and the helium abundance are approximately conserved across RD's but not across TD's, although the helium abundance is observed to change at a small fraction of the RD's. The product of plasma density times the anisotropy factor tends to be conserved across all three types, The relative directions of the velocity and field changes across all three types of discontinuity are consistent with the propagation of RD's outward from the sun, even though no such relation is predicted for TD's. The magnitude of the velocity change at RD's is smaller than that predicted by MHD theory, and the use of a two‐stream fit to the proton data reduces, but does not remove, this discrepancy. The speeds of the alpha particles and the secondary proton beam relative to the primary proton beam result in little interaction between the alphas and RD's, while the primary and secondary proton beams flow through RD's in opposite directions and have oppositely directed velocity changes. The plasma conditions at ED's show a closer resemblance to RD's than to TD's.

The term "planar magnetic structure" (PMS) refers to distinctive features in the solar wind characterized by a series of abrupt changes in the direction of the interplanetary field, with the field remaining nearly parallel to a single plane. Previous suggestions concerning the origin of PMS are (1) closed magnetic field loops arising from newly emerging, nearly parallel magnetic structures in the photosphere, (2) compression and draping of the field around a high-speed coronal mass ejection (CME), and (3) extended current sheets and/or loops from multiple helmet streamers in the corona. Four years of ISEE 3 data have been examined to establish a larger data base of PMS events and to allow a search for common features that may reveal the causes of these stmctures. A total of 33 PMS events were found and analyzed. The loop theory of PMS origins was tested by searching for a correlation between the PMSs and the electron or proton counterstreaming characteristic of closed loops or CMEs. It was found that the PMSs tended to precede rather than coincide with the CMEs. Fourteen of the PMS events (42%) were in the sheath between an interplanetary shock and a CME. Other PMS events were found to be related to crossings of the heliospheric current sheet (HCS). Sorting the events according to their association with either HCS or compression/draping ahead of fast streams (of which postshock sheaths are a subset) yields 19 events (58%) associated with compression/draping but not with HCS, 8 events (24%) associated with both compression/draping and HCS, 5 events (15%) associated with HCS but not with compression/draping, and 1 event (3%) associated with neither compression/draping nor the HCS. The conclusion is that planar magnetic structures are not closed loops of plasma from coronal mass ejections or helmet streamers. Instead, a process is postulated in which coronal mass ejections lead to the amplification and alignment of preexisting discontinuities in the ambient wind compressed by the CMEs. A possible cause of the alignment of discontinuities in the vicinity of the hellospheric current sheet is compression by lateral expansion ofCMEs in the lower corona. Cahill, 1967]. Nakagawa et al., it differed in that the plane containing the field Eight PMS events were found during the 25-month duration vectors was at an angle of ~80 ø to the Parker spiral direction. of the Sakigake mission. The spacecraft obtained Farrugia et al. argued against a magnetic-tongue model and approximately 6 hours of continuous data per day, and the PMS suggested that the UKS event may have been caused by events were generally observed to span an interval of a few compression and draping of the IMF around a high-speed hours to 6 hours, but did not extend into the prior or following plasma cloud.days. Nakagawa et al. [1989] noted that for those eight events, Crooker et al. [1993] have suggested that planar magnetic the plane defined by the field vectors was inclined to the ecliptic structures may be an interplanetary signature of a network of extended...

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Abstract. This is a report on the results of a statistical study of plasma flow characteristics before, during, and after coronal mass ejections (CMEs) observed by the instruments on board the ISEE3 spacecraft located near Earth's L1 libration point during the period 1978 to 1980. We have used parametric relationships between plasma properties (such as flow speed and proton temperature) to help distinguish between transient flow resulting from CMEs and more quiescent or quasistatic solar wind flows. A superposed epoch analysis of 29 CMEs during the period studied shows that the transient plasma flow, as we have defined it, often begins earlier and extends later than the start and end times of the CMEs based on such criteria as bidirectional flow of suprathermal electrons or energetic protons. Since the bidirectional flow is tied to the magnetic topology of the CME, our results indicate that plasma having transient flow characteristics (as we have defined them) may extend both in front of as well as behind any magnetically closed region within the CME.