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Author Alford, J. ♦ Engebretson, M. ♦ Arnoldy, R. ♦ Inan, U.
Source United States Department of Energy Office of Scientific and Technical Information
Content type Text
Language English
Subject Keyword PHYSICS ♦ LONG WAVE RADIATION ♦ MODULATION ♦ GEOMAGNETIC FIELD ♦ PULSATIONS ♦ MILLI HZ RANGE ♦ POLAR CUSP ♦ SOLAR WIND ♦ INTERPLANETARY MAGNETIC FIELDS ♦ EARTH MAGNETOSPHERE
Abstract Magnetic pulsations and quasi-periodic (QP) amplitude modulations of ELF-VLF waves at Pc 3-4 frequencies (15-50 mHz) are commonly observed simultaneously in cusp-latitude data. The naturally occurring ELF-VLF emissions are believed to be modulated within the magnetosphere by the compressional component of geomagnetic pulsations formed external to the magnetosphere. The authors have examined data from South Pole Station (L {approximately} 14) to determine the occurrence and characteristics of QP emissions. On the basis of 14 months of data during 1987 and 1988 they found that QP emissions typically appeared in both the 0.5-1 kHz and 1-2 kHz receiver channels at South Pole Station and ocassionally in the 2-4 kHz channel. The QP emission frequency appeared to depend on solar wind parameters and interplanetary magnetic field (IMF) direction, and the months near fall equinox in both 1987 and 1988 showed a significant increase in the percentage of QP emissions only in the lowest-frequency channel. The authors present a model consistent with these variations in which high-latitude (nonequatorial) magnetic field minima near the magnetopause play a major role, because the field magnitude governs both the frequency of ELF-VLF emissions and the whistler mode propagation cutoffs. Because the field in these regions will be strongly influenced by solar wind and IMF parameters, variations in the frequency of such emissions may be useful in providing ground-based diagnostics of the outer high-latitude magnetosphere. 32 refs., 13 figs.
ISSN 01480227
Educational Use Research
Learning Resource Type Article
Publisher Date 1996-01-01
Publisher Place United States
Journal Journal of Geophysical Research
Volume Number 101
Issue Number A1


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