ARCS 3 ionospheric artificial argon ion beam injections - Waves near the heavy ion gyrofrequencies

The low-frequency electric field plasma wave environment associated with artificial plasma beam injections in the ionosphere has been recorded at the main payload at distances of 0 to 1000 m away from the subpayload. An argon ion beam was injected from the subpayload periodically during the ARCS 3 experiment in the direction either antiparallel or perpendicular to the magnetic field at altitudes from 250 to 405 km. During parallel argon beam injections waves below the proton gyrofrequency were not observed. During perpendicular argon beam injections the wave spectra were broadband near the subpayload while narrow-band wave emissions near heavy ion gyrofrequencies were observed at perpendicular separation distances between 42 and 254 m. The narrow-band waves were generally ordered by the oxygen gyrofrequency (f/sub o/ = 45 Hz) although the wave spectra was different from one event to the next presumably due to the increase in perpendicular separation distance. The strongest emission lines were observed near the fourth harmonic of the oxygen gyrofrequency which was near the oxygen-helium bihybrid frequency. The narrow-band waves appeared to be associated with both the perpendicular argon ion beam and an unexpected flux of low-energy ions which peaked in energy near 15 eV and pitch anglemore » near 90/sup 0/ with respect to the magnetic field. After discussing possible free energy sources of the waves the ARCS 3 experiment is compared to previous active plasma beam experiments. copyright The American Geophysical Union 1989« less