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Average characteristics of solar wind electron velocity distributions as well as the range and nature of their variations are presented. The measured distributions are generally symmetric about the heat flux direction and are adequately parameterized by the superposition of a nearly bi‐Maxwellian function which characterizes the low‐energy electrons and a bi‐Maxwellian function which characterizes a distinct, ubiquitous component of higher‐energy electrons. An alternate self‐consistent description of the higher‐energy component is presented in terms of an unbound population of hot electrons with energy greater than some breakpoint energy of ≃60 V. The largest‐scale parameter variations appear to come most often in association with high‐speed streams. The salient electron parameter variations associated with these structures are presented and discussed. The mechanism by which interplanetary electrons conduct heat is convection of the hot component relative to the bulk speed. Arguments are presented which favor the local regulation of the solar wind heat flux at 1 AU.

Eleven passes of the ISEE satellites through the frontside terrestrial magnetopause (local time 9 -'17 h; GSM latitude 2 0 -43 0 N) have been identified, where the plasma velocity in the magnetopause and boundary laver was substantially larger than in the magnetosheath. This paper examines the nature of°the plasma flow, magnetic field, and energeticparticle fluxes in these regions, with a view to determining whether the velocity enhancements can be explained by magnetic-field reconnection.

Coronal mass ejection events (CMEs) are important occasional sources of plasma and magnetic field in the solar wind at 1 AU, accounting for approximately 10% of all solar wind measurements in the ecliptic plane during the last solar activity maximum. Previous work indicates that virtually all transient shock wave disturbances in the solar wind are driven by fast CMEs. Using a recently appreciated capability for distinguishing CMEs in solar wind data in the form of counterstreaming solar wind electron events, this paper explores the overall effectiveness of shock wave disturbances and CMEs in general in stimulating geomagnetic activity. The study is confined to the interval from mid‐August 1978 through mid‐October 1982, spanning the last solar activity maximum, when ISEE 3 was in orbit about the L1 Lagrange point 220 Re upstream from Earth. We find that all but one of the 37 largest geomagnetic storms in that era were associated with Earth passage of CMEs and/or shock disturbances, with the large majority of these storms (27 out of 37) being associated with interplanetary events where Earth encountered both a shock and the CME driving the shock (shock/CME events). Although CMEs and/or shock disturbances were increasingly the cause of geomagnetic activity as the level of geomagnetic activity increased, many smaller geomagnetic disturbances were unrelated to these events. Further, approximately half of all CMEs and half of all shock disturbances encountered by Earth did not produce any substantial geomagnetic activity as measured by the planetary geomagnetic index Kp. The geomagnetic effectiveness of Earth directed CMEs and shock wave disturbances was directly related to the flow speed, the magnetic field magnitude, and the strength of the southward (GSM) field component associated with the events. The initial speed of a CME close to the Sun appears to be the most crucial factor in determining if an earthward directed event will be effective in exciting a large geomagnetic disturbance.

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