High-resolution backscatter power observations of 440-MHz E region coherent echoes at Millstone Hill

Journal Article · Fri Feb 01 00:00:00 EST 1991 · Journal of Geophysical Research; (United States)

DOI:https://doi.org/10.1029/90JA02179· OSTI ID:5257933

Foster, J C; Tetenbaum, D ^[1]

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1. Massachusetts Inst. of Tech., Westford (USA)

A 40-{mu}s pulse length has been used to provide 10-s temporal and 6-km range resolution observations of E region coherent backscatter from the premidnight eastward electrojet region to the north of Millstone Hill. The observations can be divided into two categories: strong events in which the backscattered amplitude nears saturation and weak events in which spatial structure and large-amplitude variations are common. Calibrated observations find a typical volume scattering coefficient of {approximately}10{sup {minus}11}m{sup {minus}1} at 440 MHz during strong events with a maximum level of 9 {times} 10{sup {minus}10}m{sup {minus}1} observed for brief intervals. During less intense events the radar backscatter is modulated by {approximately}30dB in amplitude at Pc 5 frequencies (150-500 s) by waves with spatial wavelength 50-100 km. The observations support the premise that the weak irregularities grow linearly with electric field strength and reach a saturation amplitude beyond which the oscillating electric field of the Pc pulsation has little effect. The observed variation of backscattered power with range is interpreted using a geometrical model which accounts for the detailed antenna beam pattern, a magnetic aspect angle sensitivity of {minus}10 dB per degree, and a thin layer of irregularities centered at 110 km altitude. For strongly driven conditions a comparison of the range variation of backscattered power with the thin layer model suggests that the signal power becomes increasingly dominated by strong scatters confined to a narrower altitude range. The apparent altitude extent of the strongest irregularities decreases by a factor of 2 as the amplitude of the backscattered signal increases by a factor of 10.

• OSTI ID: 5257933
• Journal Information: Journal of Geophysical Research; (United States), Vol. 96:A2; ISSN 0148-0227
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
E REGION
ELECTRON DENSITY
BACKSCATTERING
CALIBRATION
ELECTRIC FIELDS
ELECTROJETS
ELECTRON DRIFT
HYDROMAGNETIC WAVES
MAGNETIC STORMS
MATHEMATICAL MODELS
RADAR
SATURATION
TWO-STREAM INSTABILITY
CURRENTS
EARTH ATMOSPHERE
ELECTRIC CURRENTS
INSTABILITY
IONOSPHERE
MEASURING INSTRUMENTS
PLANETARY IONOSPHERES
PLASMA INSTABILITY
PLASMA MICROINSTABILITIES
RANGE FINDERS
SCATTERING
640201* - Atmospheric Physics- Auroral
Ionospheric
& Magetospheric Phenomena