Observations are reported of waves generated by 2-, 4- and 8-keV electron beams with currents up to 100 mA, emitted by an accelerator carried in a rocket to ionospheric heights. Observations were made from a separated payload, and attempted from the ground. The strongest signals, which are observed near or in the beam, are low-frequency signals in the range 100 Hz to 1 kHz, which reach peaks of 1 V/m. There is relatively strong emission in the upper whistler mode range (100 kHz-fce) for the 100-mA electron pulses, and about half of the 10-mA electron pulses. These whistler mode signals appear identical to those observed to indicate beam plasma discharge (BPD) in laboratory work. If this indicates that BPD is occurring in these experiments, then BPD is ignited at about 20 times lower current than in a large plasma chamber. Harmonics of the plasma frequency with amplitudes comparable to the fundamental are observed in and near the beam. Field strengths of all these modes are reported. For the whistler mode and plasma frequency emissions, ''strong'' is used above in a relative sense. The high-frequency signals i.e., those above 100 kHz, are too weak to have much effect on the beam, or to appreciably accelerate ambient electrons. Natural low-frequency emissions were also observed in flight. No signals generated by the beam were observed on the ground. |