Large-scale plasma irregularities and airglow enhancements from ionospheric heating
Ionospheric modification with high power radio waves may generate plasma irregularities and airglow clouds. Large scale irregularities are produced in a convecting F-layer by a mechanism called the plasma-relaxation-oscillator. When a continuous beam of powerful electromagnetic waves heats the ionosphere, a cavity is produced by thermal pressure gradients. The cavity drifts under the influence of ambient electric fields causing the vertically-incident, radio beam to be refracted from the zenith. At some point, the cavity can no longer capture the beam and it returns to the zenith to form another cavity. This relaxation process repeats to yield irregularities on the scale of the heater beam diameter. Airglow enhancements are produced by energetic electrons accelerated out of the heated region. Large amplitude electrostatic waves may be excited by linear mode coupling, by parametric decay instabilities, and by strong plasma turbulence. This occurs near the point where the plasma frequency of the ionosphere matches wave frequency. The electrostatic waves accelerate ambient electrons to high enough energy to collisionally excite ambient oxygen atoms. Clouds of enhanced red-line (630.0 nm) and green-line (557.7 nm) emissions have been recorded with low-light-level imaging systems located at Arecibo, Puerto Rico. Comparison of the Imager data with data from the Arecibo incoherent scatter radar shows that artificial airglow clouds are physically tied to the density cavities and to regions of enhanced electrostatic waves by the earth's magnetic field lines. At currently available power levels (around 80 MW effective radiated power), HF modification yields 10-30% fluctuations in density and 10-100 Rayleigh enhancements in airglow intensity.
- Research Organization:
- Naval Research Lab., Washington, DC (United States)
- OSTI ID:
- 7027710
- Report Number(s):
- AD-P-006503/7/XAB
- Resource Relation:
- Other Information: This article is from 'Conference Proceedings on Ionospheric Modification and its Potential to Enhance or Degrade the Performance of Military Systems held in Bergen, Norway on 28-31 May 1990, AD-A239 823, p13-1 thru p13-8
- Country of Publication:
- United States
- Language:
- English
Similar Records
Excitation of artificial airglow by high power radio waves from the SURA ionospheric heating facility
The ionospheric focused heating experiment
Related Subjects
GENERAL PHYSICS
AIRGLOW
IONOSPHERE
HIGH-FREQUENCY HEATING
PLASMA DENSITY
COMPARATIVE EVALUATIONS
ELECTRIC FIELDS
ELECTRON DENSITY
ELECTROSTATICS
F REGION
LAYERS
MAGNETIC FIELDS
OXYGEN
PLASMA DRIFT
PLASMA WAVES
PRESSURE GRADIENTS
RADAR
RADIOWAVE RADIATION
RELAXATION
TURBULENCE
EARTH ATMOSPHERE
ELECTROMAGNETIC RADIATION
ELEMENTS
EVALUATION
HEATING
MEASURING INSTRUMENTS
NONMETALS
PLANETARY IONOSPHERES
PLASMA HEATING
RADIATIONS
RANGE FINDERS
661320* - Auroral
Ionospheric
& Magnetospheric Phenomena- (1992-)