Origin of short-period (30-300 s) Doppler frequency fluctuations of lower F region reflections in the equatorial electrojet region

Journal Article · Sun Dec 01 00:00:00 EST 1991 · Radio Science; (United States)

DOI:https://doi.org/10.1029/91RS02021· OSTI ID:5812788

Sastri, J H; Ramesh, K B; Rao, J V.S.V.; Somayajulu, V V ^[1]

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1. Indian Institute of Astrophysics, Bangalore (India) ISRO, Vikram Sarabhai Space Centre, Trivandrum (India)

Measurements of phase path P of lower F-region reflections at normal incidence at Kodaikanal revealed the ubiquitous presence of 30-300-s quasi-sinusoidal variations in the time rate of change of phase path, P (Doppler frequency shift) during day time. A study is made of the influence of the irregularities in the equatorial electrojet on the P fluctuations using simultaneous observations of F-region phase path at Kodaikanal and of equatorial electrojet with the VHF-backscatter radar at Thumba. It is shown that the spectral content of the Doppler fluctuations (quantified in terms of variance, sigma squared computed from P time series synthesized through FFT exp -1 (FFT) in the chosen period bands, 30-300 s/30-120 s of the FFT of original P times series) bears a significant positive linear relationship to the horizontal phase velocity of electrojet irregularities (3-m scale size) on a hourly basis. This result is in consonance with earlier findings (Sastri et al., 1990) of a significant linear relationship of sigma squared to the electrojet strength (estimated from H-field data) and a practical cessation of the P fluctuations at times of disappearance of Esq on ionograms (partial/complete counterelectrojet). The present work substantiates the interpretation that the short-period Doppler-frequency fluctuations are due to phase-path changes imposed on lower F region reflections by the refractive-index variations associated with the convective motions of plasma density irregularities (type I and II) in the daytime equatorial electrojet. 49 refs.

• OSTI ID: 5812788
• Journal Information: Radio Science; (United States), Vol. 26; ISSN 0048-6604
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ELECTROJETS
PLASMA DENSITY
BACKSCATTERING
DOPPLER EFFECT
F REGION
FOURIER TRANSFORMATION
RADAR
REFLECTION
TIME-SERIES ANALYSIS
VARIATIONS
WAVE PROPAGATION
CURRENTS
EARTH ATMOSPHERE
ELECTRIC CURRENTS
INTEGRAL TRANSFORMATIONS
IONOSPHERE
MATHEMATICS
MEASURING INSTRUMENTS
PLANETARY IONOSPHERES
RANGE FINDERS
SCATTERING
TRANSFORMATIONS
661320* - Auroral
Ionospheric
& Magnetospheric Phenomena- (1992-)