Observations of waves artificially stimulated by an electron beam inside a region with auroral precipitation

The POLAR 5 sounding rocket, launched from Andoya, Norway on 1 February 1976 was of a 'mother-daughter' configuration. An electron accelerator, mounted on the 'daughter' produced a pulsed electron beam with currents up to 130 mA and electron energies up to 10 keV. The waves, artificially stimulated by the injected electron beams, was studied using wave receivers, mounted on the 'mother'. The receivers covered the frequency range from 0.1 kHz to 5 MHz. In addition to the stimulated waves observed during beam injection, enhanced wave emissions were observed 10-20 ms after the end of beam injection. This emission seemed to be relatively independent of whether the electron beam is launched up or down along the geomagnetic field. The high frequency emission observed after beam injection is found to be correlated with the passage through an auroral arc. In particular this emission is closely correlated with the flux of 4-5 keV auroral electrons. The low frequency emissions observed after beam injection are concentrated in two bands below the lower hybrid frequency. Different mechanisms for explaining the observed time delays between the beam injection and the observation of the emissions are discussed. (author)