Simultaneous measurements of HF-enhanced plasma waves and artificial field-aligned irregularities at Arecibo
- Rice Univ., Houston, TX (USA)
- Aerospace Corp., Los Angeles, CA (USA)
Two radar systems with beams intersecting in the HF-modified F region were used to simultaneously measure HF-enhanced plasma lines (HFPLs) and artificial geomagnetic field-aligned irregularities (AFAIs). The Arecibo 430-MHz radar was used for the HFPL observations, and a portable 49.92-MHz backscatter radar was deployed on the island of Guadeloupe to monitor the AFAIs. The experiment was desgined to examine the degree to which HF-induced plasma turbulence influences the development of AFAIs. When the HF beam is stepped up in power, sustained HFPLs and AFAIs are first observed at the same HF power level, indicating that ponderomotively driven instabilities may be involved in the early time development of AFAIs. As the HF power is increased, the HFPL backscatter power begins to saturate at {approximately}70 MW effective radiated power (ERP). However, the backscatter from AFAIs is linearly dependent on HF power, even at the highest (120 MW ERP) HF power levels available at Arecibo. This suggests that additional processes may contribute to the development of AFAIs. For example, ponderomotively driven instabilities may give rise to weak geomagnetic field-aligned irregularities that are subsequently driven unstable by processes excited near the upper hybrid resonance. It is also likely that AFAIs greatly impact the development of HF-induced plasma turbulence at late times (>1 s) following HF turn-on. Once the ionosphere is preconditioned by high-power HF modifications, AFAIs and HFPLs can be simultaneously sustained at a much lower HF power level than that needed to originally excite them. The nature of the preconditioning process is currently not well understood. New theoretical initiatives are clearly needed to guide future experimental activity in this area.
- OSTI ID:
- 5444376
- Journal Information:
- Journal of Geophysical Research; (United States), Vol. 95:A9; ISSN 0148-0227
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GENERAL PHYSICS
F REGION
PLASMA DENSITY
PLASMA WAVES
BACKSCATTERING
DIAGNOSTIC TECHNIQUES
GEOMAGNETIC FIELD
MODIFICATIONS
PLASMA INSTABILITY
RADAR
RADIOWAVE RADIATION
TURBULENCE
EARTH ATMOSPHERE
ELECTROMAGNETIC RADIATION
INSTABILITY
IONOSPHERE
MAGNETIC FIELDS
MEASURING INSTRUMENTS
PLANETARY IONOSPHERES
RADIATIONS
RANGE FINDERS
SCATTERING
640201* - Atmospheric Physics- Auroral
Ionospheric
& Magetospheric Phenomena