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Kilometric radiation power flux dependence on area of discrete auroraKilometer wavelength radiation, measured from distant positions over the North Pole and over the Earth's equator, was compared to the area of discrete aurora imaged by several low-altitude spacecraft. Through correlative studies of auroral kilometric radiation (AKR) with about two thousand auroral images, a stereoscopic view of the average auroral acceleration region was obtained. A major result is that the total AKR power increases as the area of the discrete auroral oval increases. The implications are that the regions of parallel potentials or the auroral plasma cavities, in which AKR is generated, must possess the following attributes: (1) they are shallow in altitude and their radial position depends on wavelength, (2) they thread flux tubes of small cross section, (3) the generation mechanism in them reaches a saturation limit rapidly, and (4) their distribution over the discrete auroral oval is nearly uniform. The above statistical results are true for large samples collected over a long period of time (about six months). In the short term, AKR frequently exhibits temporal variations with scales as short as three minutes (the resolution of the averaged data used). These fluctuations are explainable by rapid quenchings as well as fast starts of the electron cyclotron maser mechanism. There were times when AKR was present at substantial power levels while optical emissions were below instrument thresholds. A recent theoretical result may account for this set of observations by predicting that suprathermal electrons, of energies as low as several hundred eV, can generate second harmonic AKR. The indirect observations of second harmonic AKR require that these electrons have mirror points high above the atmosphere so as to minimize auroral light emissions. The results provide evidence supporting the electron cyclotron maser mechanism.
Document ID
19890013669
Acquisition Source
Legacy CDMS
Document Type
Contractor Report (CR)
Authors
Saflekos, N. A. (Texas Univ. San Antonio., United States)
Burch, J. L. (Southwest Research Inst. San Antonio, TX., United States)
Gurnett, D. A. (Iowa Univ. Iowa City., United States)
Anderson, R. R. (Iowa Univ. Iowa City., United States)
Sheehan, R. E. (Boston Coll. Chestnut Hill, MA., United States)
Date Acquired
September 5, 2013
Publication Date
January 1, 1989
Subject Category
Geophysics
Report/Patent Number
NASA-CR-184993
NAS 1.26:184993
Accession Number
89N23040
Funding Number(s)
CONTRACT_GRANT: NAGW-1254
CONTRACT_GRANT: NAG5-227
CONTRACT_GRANT: NSF ATM-85-21590
CONTRACT_GRANT: NSF ATM-88-05819
CONTRACT_GRANT: NSF ATM-86-46122
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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