The CRRES AA2 release: HF wave-plasma interactions in a dense Ba{sup +} cloud
- Geospace Research, Inc., El Segundo, CA (United States)
- Arecibo Observatory (Puerto Rico)
- Phillips Lab., Hanscom Air Force Base, MA (United States)
An ionospheric chemical release, designated AA2, was performed on July 12, 1992, as part of the NASA Combined Release and Radiation Effects Satellite (CRRES) El Coqui rocket campaign. The purpose of the AA2 experiment was to study the interaction between a powerful radio wave and a high ion mass (Ba{sup +}), {open_quotes}collisionless{close_quotes} plasma. Approximately 35 kg of Ba were explosively released near the center of the Arecibo high-frequency (HF) beam at 253 km altitude. This was the largest Ba release of the CRRES experiments; it yielded a distinctive ionospheric layer having a maximum plasma frequency of 11 MHz. At early times the HF beam produced the strongest Langmuir waves were observed to be excited principally at the upshifted plasma line and only weakly excited waves were apparent at the downshifted plasma line. The upshifted plasma-line spectrum contained a dominant peak at the {open_quotes}decay line,{close_quotes} that is, at the frequency 430 MHz + f{sub HF} - {sigma}, where {sigma} is close to the Ba{sup +} ion-acoustic frequency ({approximately}2kHz). Downshifted plasma-line echoes occurred at frequencies near 403 MHz-f{sub HF} and 430 MHz- f{sub HF} - 1 kHz and exhibited little or no signal strength at the decay line (430 MHz - f{sub HF} + {sigma}). During an initial period of intense upshifted plasma-line excitation, the power asymmetry between the upshifted and downshifted plasma lines was of the order of 10{sup 5} at the decay line. The upshifted plasma line was accompanied by strong HF-enhanced ion waves that were present only at the downshifted acoustic sideband. After geomagnetic field-aligned irregularities formed in the plasma the amplitudes of the upshifted and downshifted plasma lines equalized, and each exhibited spectra characteristic of the parametric decay instability. At early times in the Ba{sup +} plasma the symmetry of wave excitation anticipated for a parametric instability in a stationary, homogeneous plasma was absent.
- OSTI ID:
- 175847
- Journal Information:
- Journal of Geophysical Research, Vol. 100, Issue A9; Other Information: PBD: 1 Sep 1995
- Country of Publication:
- United States
- Language:
- English
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