Oxygen Gyrofrequency Research Articles

Ion beam produced plasma waves observed by the δ n/n plasma wave receiver during the porcupine experiment

The Porcupine sounding rocket consisted of a central instrumented payload with 4 smaller payloads ejected in the radial direction. One of the smaller payloads contained a xenon ion gun which directed a 200eV Xe+ ion beam roughly perpendicular to the magnetic field. During the ion gun exercises a variety of plasma waves were observed by the δ n/n experiment on the central spacecraft. For small separations betwen the ion gun and the plasma wave receivers, intense and very narrow band emissions were observed just above harmonics of the hydrogen gyrofrequency extending from n=1 to at least n=11 and perhaps to much higher harmonics. Additional structure at the helium gyrofrequency was also observed and the width of each spectral line was the order of the oxygen gyrofrequency. The fastest growing modes were at n=5 or 6. For larger separations between the ion gun and plasma wave receiver, band limited emissions were observed between the NO+ and O+ lower hybrid frequencies. The intense ion cyclotron harmonic waves observed for short separations are very similar to plasma waves observed at high altitudes in ion conics by the S3-3 satellite. In those examples, natural ion beams, which were nearly perpendicular to the magnetic field, produced plasma waves between harmonics of the hydrogen gyrofrequency and the most intense waves occurred between n=3 and n=7. Hence the ion beam experiment is directly applicable to understanding ion beams within the magnetosphere.

Ion cyclotron waves generated by an ionospheric barium injection

A shaped charge, barium, plasma injection experiment was performed in June 1976 at the ERDA Kauai test facility. The barium was injected perpendicular to the geomagnetic field at an altitude of 450 km. The second stage of the rocket, located approximately 1.2 km from the point of detonation, contained a payload to measure dc and ac electric fields using a dual spherical probe antenna. A variety of plasma waves were detected for approximately 20 s following the detonation. The initial impulse generated ion cyclotron waves at the Ba+, O2+, Al+, OH+, and O+ gyrofrequencies. No evidence for a Doppler shift was observed. This was followed by a time period during which ion cyclotron waves were observed in passbands between the barium gyrofrequency harmonics up to the oxygen gyrofrequency. At the high‐frequency end of this range the spectrum is essentially continuous, i.e., similar to an ion sound wave spectrum.