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Statistical Study of Auroral Kilometric Radiation Fine Structure Striations Observed by PolarWe have conducted a statistical survey of a semirandom sample of the auroral kilometric radiation (AKR) data observed by the plasma wave instrument wideband receiver on board the Polar spacecraft. We have determined that AKR fine structure patterns with very narrowband, negative drifting striations occur in approximately 6% of the high-resolution wideband spectrograms when AKR is present. Positive sloping striations are also observed, but at a much lower rate. More than 8200 AKR stripes have been scaled. The stripes are predominantly found in the 40 to 215-kHz frequency range and have a frequency extent of about 4 kHz and a duration of usually less than 2 s. The majority of the stripes have drift rates between -8 and -2 kHz/s, with a peak in the distribution between -6 and -4 kHz/s. There is also a much smaller group of striations with positive drift rates of up to about 5 or 6 kHz/s. We have further investigated the change of drift rate with frequency. Almost all striations are observed in the lowest two frequency bands of the wideband receiver (f < 215 kHz). There is an increase in the statistical drift rate with increasing frequency. The statistical slope of the striations increases with frequency from about -4.4 kHz/s at 75 kHz to about -5.7 kHz/s at 170 kHz. This frequency dependence of the drift rate is consistent, under certain conditions, with a production mechanism stimulated by an upward propagating electromagnetic ion cyclotron wave, as had been suggested earlier. However, such a changing drift rate is also compatible with a stimulated source region that propagates upward along the magnetic field line at the velocity of an ion beam accelerated by a local, upward directed electric field, as is typically observed in the auroral region. An explanation for this association is not apparent at this time.
Document ID
20020033989
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Menietti, J. D.
(Iowa Univ. Iowa City, IA United States)
Persoon, A. M.
(Iowa Univ. Iowa City, IA United States)
Pickett, J. S.
(Iowa Univ. Iowa City, IA United States)
Gurnett, D. A.
(Iowa Univ. Iowa City, IA United States)
Date Acquired
August 20, 2013
Publication Date
August 1, 2000
Publication Information
Publication: Journal of Geophysical Research
Publisher: American Geophysical Union
Volume: 105
Issue: A8
ISSN: 0148-0227
Subject Category
Geophysics
Report/Patent Number
Paper-1999JA000389
Funding Number(s)
CONTRACT_GRANT: NAG5-7943
Distribution Limits
Public
Copyright
Other

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