An investigation of wave-particle interactions and particle dynamics using electron beams injected from sounding rockets

Electrons with energy up to 40 kV have been injected into semi-trapped orbits from sounding rockets at Wallops Island, Virginia, and at Fort Churchill, Manitoba, Canada. By directing the rocket trajectory to have a horizontal component which in direction and speed matched the bounce displacement of the injected electrons, it was possible to detect conjugate echoes at Wallops and possibly at Churchill, and to study the distribution of the echoes in space, time and energy. By combining observations of many echoes, a composite picture can be obtained of the beam patterns. Atmospheric scattering at the conjugate point of Wallops island has been extensively studied, and the process produces a scale width of 5–10 m, but with an echo intensity which is only 10% of theoretical estimates. In the Wallops experiments, a doublet hump appeared in the echoes which is not understood. Models of the magnetic fields are used to predict the bounce displacement, and by comparison with the observations to evaluate other effects such as electric field drift integrated over a complete bounce period. Preliminary evaluation of the Churchill results indicate the presence of substantial residual effects, which may be electric field drifts. The artificial beam injection was observed to change natural electron precipitation in the 20–40 keV range. The process of rocket neutralization, beambeam interactions, and electromagnetic radiation from the beams has been studied and has been part of the Echo program.Presented for the author by R. L. Arnoldy at the Workshop on Controlled Magnetospheric Experiments, Kyoto, Japan, Sept., 1973.