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Magnetic field orientations in Saturn's upper ionosphere inferred from Voyager radio occultations

 

作者: David P. Hinson,  

 

期刊: Journal of Geophysical Research: Space Physics  (WILEY Available online 1984)
卷期: Volume 89, issue A1  

页码: 65-73

 

ISSN:0148-0227

 

年代: 1984

 

DOI:10.1029/JA089iA01p00065

 

数据来源: WILEY

 

摘要:

Dual‐wavelength radio observations during the occultations of Voyagers 1 and 2 provided 3.6‐cm and 13‐cm data on Saturn's ionospheric irregularities at two locations. Spectra of the weak fluctuations in amplitude and phase can be interpreted using the theory for scattering from a power law spectrum of anisotropic irregularities embedded in a thin screen. Comparisons of measured scintillation spectra with the theory produced least squares solutions for four parameters which characterize the ionospheric irregularities: (1) the axial ratio, (2) the orientation, (3) the power law exponent of the spatial spectrum, and (4) the magnitude of the spatial variations in electron density. Scattering was observed from irregularities of approximate size 2–60 km; these lower and upper limits result from noise limitations and the method of analysis, respectively, and do not represent either an inner or outer scale. Within this range of length scales, the three‐dimensional spatial spectrum obeys an inverse power law with exponent near 3.5, and the fractional variations in electron density are about 10–20%. All observed irregularities appear to be anisotropic with axial ratios greater than 4∶1. Magnetic field orientations in Saturn's ionosphere were inferred from the direction of alignment of the anisotropic irregularities. When used as a test of Saturnian magnetic field models, the occultation measurements generally confirm the accuracy of the model predictions but also suggest that a small adjustment of model parameters might improve the field r

 

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