A survey of the equatorial pitch angle distributions of energetic electrons is provided for all local times out to radial distances of 20 RE on the night side of the earth and to the magnetopause on the day side of the earth. In much of the inner magnetosphere and in the outer magnetosphere on the day side of the earth, the normal loss cone distribution prevails. The effects of drift shell splitting (that is, the appearance of pitch angle distributions with minimums at 90°, called butterfly distributions) become apparent in the early afternoon magnetosphere at extended distances, and the distribution is observed in to 5.5 RE in the nighttime magnetosphere. Inside ∼9 RE the pitch angle effects are quite energy dependent. Beyond ∼9 RE in the premidnight magnetosphere during quiet times the butterfly distribution is often observed with j⊥/j∥ < 1/100. It is shown that these electrons cannot survive a drift to dawn without being considerably modified. The role of substorm activity in modifying these distributions is identified.

Bursts of energetic protons, 100–1300 keV, were observed on Ogo 5 in the magnetosheath and upstream wave region beyond the earth's bow shock during periods of generally enhanced solar and magnetic activity in 1968. From these data, we present the first comprehensive study of energetic protons in the magnetosheath. These magnetosheath protons are found to be directional with the peak flux directed downstream. Typical downstream‐to‐upstream flux ratios are from 10/1 to 20/1 in most regions but often as great as 100/1 near the afternoon magnetopause. The fluxes correlate roughly with magnetic activity. The downstream flux can be expressed as j(> 100 keV) = 500 × 100.412Kp/cm² sr s to about an order of magnitude. Peak unidirectional fluxes near the magnetopause are often similar in spectra and intensity to the peak intensities of trapped fluxes in the nearby magnetosphere. Enhanced proton fluxes occur in the sheath in correlation with depressions in the sheath magnetic field and in correlation with enhanced turbulence. Often at such times, magnetopause boundary layer effects are observed. Energetic proton bursts, in agreement with earlier observations (Lin et al., 1974), are also observed in the upstream wave region beyond the shock, predominately on the morning side of the earth. They correlate well with the wave observations; however, on occasion, they are offset as much as 10 min in time. Directional observations indicate downstream‐to‐upstream directed flux ratios of 10/1 as being typical of the upstream wave region. The directional anisotropies in both the sheath and the upstream wave regions are largely explained by combinations of the Compton‐Getting effect, proton flux spatial gradients, and the free streaming of protons along field lines from an upstream source region. Possible sources of the energetic magnetosheath protons are magnetospheric escape or the energization of low‐energy protons in the magnetosheath, shock, and/or upstream wave region. No strong preference is presently ascribed to any one source.

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An account is given of measurements of electrons made by the LLNL magnetic electron spectrometer (60–3000 keV in seven differential energy channels) on the Ogo 5 satellite in the earth's outer‐belt regions during 1968 and early 1969. The data were analyzed to identify those features dominated by pitch angle and radial diffusion; in doing so all aspects of phase space covered by the data were studied, including pitch angle distributions and spectral features, as well as decay rates. The pitch angle distributions are reported elsewhere. The spectra observed in the weeks after a storm at L ∼3–4.5 show the evolution of a peak at ∼1.5 MeV and pronounced minima at ∼0.5 MeV. The observed pitch angle diffusion lifetimes are identified as being the shortest decays observed and are found to be highly energy and L dependent with minimum lifetimes of ∼1–2 days occurring at L ∼3–4.5. Two contiguous periods of decay, following the intense storm injection on October 31 and November 1, were analyzed in terms of radial diffusion. Significant differences were found between the derived values of DLL for the two periods; also significant energy dependence shows in the results. Although the values of DLL vary by about a factor of 10, representative values are 0.3 day−1 at L=6, 0.06 at L=4, 0.015 at L=3, and 0.001 at L=2.5. Despite the wide variation of many prior results in the literature, there is a family of results in approximate agreement with the present results. By noting the variations in DLL, as a function of the invariant quantities, we are able to order a fair body of previous results with our new results.

Energetic‐particle pitch angle data and vector magnetometer data, measured along the Ogo 5 inbound orbit near midnight on three magnetically quiet days, August 2, 4, and 25, 1968, were used to infer the magnetic tail field configuration for each day. For the first 2 days the particles, when initially detected, showed isotropic pitch angle distributions (PAD's) (indicative of nonadiabatic motions resulting from the breakdown of the guiding center invariants µ and J) but later made rapid transitions to the butterfly PAD (indicative of adiabatic guiding center motion). The lower‐rigidity particles made the PAD transitions first and were followed in turn by the higher‐rigidity particles as Ogo neared the earth. We have used a simple algebraic model which has allowed us to fit both the magnetic field and the pitch angle transition data. For the latter data fit, the detailed particle trajectories were followed along the model field lines to the neutral sheet. The particles were required to execute adiabatic guiding center motion if they were started from positions on the satellite orbit nearer earth than the point of observed changes in the PAD. They were required to undergo nonadiabatic motion at some part of their trajectory if they were started at a point on the satellite orbit farther from the earth than the PAD transition point. The results are presented in terms of model coefficients for each day. The model fields are plotted, the cross‐tail currents are derived, and particle motion is studied in the model fields. It was found that 79‐keV electrons were in the nonadiabatic mode when they were on field lines that crossed the neutral sheet beyond 11 RE on August 2; on August 25, a less taillike day, this point was 17 ± 1 RE. For 10‐keV protons the inferred points are 8.5 and 11.7 RE, respectively, for these 2 days. This is interesting because protons of about this energy carry a large part of the cross‐tail current. It is expected that when data from particles of a wide range of rigidity are available, this method of inferring the tail field configuration should be very powerful.