Near‐equatorial, high‐resolution measurements of electron precipitation at L ≃6.6

<jats:p>Previous studies of precipitating electrons at low altitudes in the auroral zone have shown that such precipitation is impulsive and highly fluctuating (time scales of seconds). It is also generally supposed that energetic electron precipitation results from wave‐particle scattering that occurs primarily near the outer zone (<jats:italic>L</jats:italic>=5‐8) equatorial plane. In contrast to prior low‐altitude measurements, however, nearly all previously reported measurements made in the near‐equatorial regions have been quite slow, with loss cone sampling times of minutes. This paper presents correlated measurements of Technical University of Denmark auroral zone riometer data (20‐s sampling times) and Los Alamos Scientific Laboratory high‐resolution (8‐ms sampling, 10‐s rotation) >30‐keV electron measurements made at geostationary orbit during the course of magnetospheric substorms. Prior to substorm expansion onset, substantial evidence is found to support the concept of a substorm growth phase. Following the expansion phase onset and the concomitant injection of newly energized electrons into the outer magnetosphere, it is possible to examine equatorial electron fluxes in the loss cone for cases of weak pitch angle diffusion as well as for cases of strong pitch angle diffusion. During strong diffusion events, it is found that precipitating electron fluxes are highly fluctuating and impulsive at the minimum loss cone sampling time of 10 s. For such event periods the pitch angle distribution outside the loss cone is nearly flat (isotropic flux), the absolute electron intensity (>30 keV) is near ‘saturation’ (<jats:italic>j</jats:italic> ∼5 × 10<jats:sup> 7</jats:sup> cm<jats:sup> −2</jats:sup> s<jats:sup> −1</jats:sup> sr<jats:sup> −1</jats:sup>), and the 20‐MHz conjugate riometer intensity is very high (5–15 dB). These results demonstrate that equatorial wave‐particle interactions do not build up steadily and gradually but rather that they develop in an impulsive or sporadic way. Thus these observations are quite consistent with low‐altitude results and probably relate equatorial phenomena to such ionspheric phenomena as pulsating aurora and fluctuating auroral zone bremsstrahlung X rays.</jats:p>