A comparative study of imaging and broad-beam riometer measurements: The effect of spatial structure on the frequency dependence of auroral absorption

Journal Article · Tue Oct 01 00:00:00 EDT 1991 · Journal of Geophysical Research; (United States)

DOI:https://doi.org/10.1029/91JA01827· OSTI ID:5812929

Rosenberg, T J; Detrick, D L ^[1]; Venkatesan, D; van Bavel, G ^[2]

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1. Univ. of Maryland, College Park (United States)
2. Univ. of Calgary, Alberta (Canada)

Observations of the spatial structure and motion of auroral absorption regions obtained with the 38.2-MHz imaging riometer for ionospheric studies (IRIS) at South Pole Station, Antarctica, have been used to simulate the absorption that should be measured by the 20.5-, 30-, 38.2-, and 51.4-MHz broad-beam riometers also operating at the station. The simulation assumes that the absorption measured by each of the 49 narrow IRIS beams obeys the absorption-frequency relationship, a(f) {approximately} f{sup {minus}2}, predicted by generalized magnetoionic theory to apply at altitudes above {approximately}70 km. Excellent agreement to quite fine detail is obtained between the simulated and measured broad-beam absorption profiles. The power law exponents derived from absorption ratios, or from least squares fits to the absorption as a function of frequency, range between 1 and 2 and are essentially the same for simulated and measured broad-beam data, to within the experimental and computational uncertainties. These results indicate that spatial gradients in the absorption regions, corresponding to similar features in the electron precipitation source, are the cause of deviations from the inverse-square frequency dependence noted previously in broad-beam riometer measurements and erroneously interpreted as signifying very high energy electron precipitation and enhanced ionization at much lower altitudes.

• OSTI ID: 5812929
• Journal Information: Journal of Geophysical Research; (United States), Vol. 96:A10; ISSN 0148-0227
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
POLAR-CAP ABSORPTION
FREQUENCY DEPENDENCE
AURORAL ZONES
COMPARATIVE EVALUATIONS
ELECTRON PRECIPITATION
MORPHOLOGY
MOTION
POLAR REGIONS
RADIO NOISE
SIMULATION
ABSORPTION
CHARGED-PARTICLE PRECIPITATION
ELECTROMAGNETIC RADIATION
EVALUATION
NOISE
RADIATIONS
RADIOWAVE RADIATION
661320* - Auroral
Ionospheric
& Magnetospheric Phenomena- (1992-)