HF produced ionospheric electron density irregularities diagnosed by UHF radio star scintillations
HF-waves incident on an overdense (HF-frequency < penetration frequency) ionosphere are known to produce large scale electron density irregularities. It is predicted that similar irregularities are formed during underdense HF-modification. The propagation of UHF radio waves originating from radio stars will be affected by such irregularities in the ionosphere. The interest in a scintillation experiment is twofold. One may obtain information on the electron density irregularies and one may learn about the propagation of radio waves through such a perturbed medium. A thin screen (diffractive) theory is derived which allows to draw conclusons on the electron density irregularities from the intensity fluctuations measured on the ground if the phase perturbations are much less than one radian. Since radio stars suitable for scintillation measurements at UHF are very faint an antenna with a large collection area is required. The observations reported in this dissertation were performed with the 300m diameter spherical reflector of the Arecibo Observatory. Successful observations were performed at 430 MHz and at 1400 MHz. Intensity fluctuations at such high frequencies measured with a large antenna suffer severe filtering in the thin phase screen regime. The theory presented in this dissertation includes these filtering effects. Many observations agree with the predictions of that theory. Some observations indicate that refraction effects have to be included to explain the data. HF-induced electron density irregularities were only observed during overdense heating.
- Research Organization:
- Rice Univ., Houston, TX (USA)
- OSTI ID:
- 6939666
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
Ionospheric
& Magetospheric Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ANTENNAS
EARTH ATMOSPHERE
ELECTRICAL EQUIPMENT
ELECTROMAGNETIC RADIATION
ELECTRON DENSITY
EQUIPMENT
FLUCTUATIONS
FREQUENCY RANGE
GHZ RANGE
GHZ RANGE 01-100
HEATING
IONOSPHERE
MHZ RANGE
MHZ RANGE 100-1000
PLANETARY IONOSPHERES
RADIATIONS
RADIOWAVE RADIATION
SCINTILLATIONS
STARS
VARIATIONS
WAVE PROPAGATION