Energetic particle activity at 5-min and 10-s time resolution in the magnetotail and its relation to auroral activity

Using data from the JHU/APL experiments on the Imp 7 and 8 spacecraft, we have examined several energetic (E/sub p/< or approx. =0.3 MeV, E/sub e/> or approx. =0.2 meV) particle bursts associated with substorm events in the magnetotail. During these events the spacecraft were within approx.10 R/sub E/ of the nominal neutral sheet (D/sub S/Mapprox. =0) and within approx.20 R/sub E/ of each other. Individual proton an electron bursts observed by both spacecraft do not always coincide nor does magnetotail activity correlate strongly with auroral activity on time scales less than approx.1 hour. This may be a consequence of the magnetic connection of the spacecraft to the region producing the energetic particles. Strong proton anisotropies are observed during most events. Several of the bursts exhibit rapid onsets and slow, near-exponential decays with repetitive injections. Combining magnetic field and particle measurements on Imp 8, we can determine the pitch angle distributions with a time resolution of approx.10 s. During intense particle bursts the 0.3-MeV protons exhibit unidirection of bidirectional anisotropies along the magnetic field. At othe times, the protons exhibited anisotropies indicating motion from dawn to dusk across field lines. Both types of proton anisotropies persist for minutes, suggesting that the mechanism generating them must be active for at least as long. The energetic electrons tend not to be anisotropic, at least to the same degree as the protons. The data suggest the presence of small localized acceleration regions in the magnetotial which are observable when magnetically connected to the spacecraft. Little convincing evidence is found for a single neutral line extending across the width of the magnetotail