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Occurrence of Equatorial F Region Irregularities: Evidence for Tropospheric SeedingWe present a new gap-free version of the seasonal and longitudinal 0 (s/l) variations of P(sub EFI), the equatorial F region irregularity (EFI) occurrence probability, based on data from the AE-E spacecraft. The agreement of this and three earlier partial P(sub EFI) patterns verifies all four. We reinterpret another earlier gap-ridden pattern, that of D(bar)(sub RSF), a topside ionogram index of average darkening by range spread F. We compare it with P(sub EFI) and, using ionosonde radio science considerations, we conclude that D(bar)(sub RSF) = P(sub EFI) times a factor depending on the average number of topside plasma bubbles visible to the ionosonde. The s/l variations of D(baar)(sub RSF) thus imply s/l variations in the average spacing of bubbles, whose seeds have an occurrence probability pattern P(sub seed). For discussion we assume P(sub EFI) = P(sub inst)P(sub seed) is the pattern of F region instability. The P(sub EFI) pattern, which is by definition independent of seed and/or bubble spacing, is far too complex to be explained by the dominant paradigm, that of changes in P(sub inst) by simple changes in the F region altitude and/or north-south asymmetry. We examine evidence behind this dominance, and find it unconvincing. Both the asymmetry and sunset-node/altitude hypotheses of 1984 and 1985, respectively, seem to be partly based on misunderstood data, and their features appear displaced in time and space from those of our repeatable P(sub EFI) pattern. In contrast, if P(sub seed) variations influence the P(sub EFI) pattern and depend on thermospheric gravity waves from tropospheric convection near the dip equator, then the seasonal maxima (minima) Of P(sub EFI) could be explained, since they all occur above relatively warm (cold) surface features, where convection is maximal (minimal). Also, the hypothesis of the dominance of the P(sub seed) term could explain an unusual December/January P(sub EFI) maximum in the deep, wide, normal Pacific minimum in the one data set obtained in El Nino years. Based on the experiments we consider, we predict that the s/l variations Of P(sub seed) will be found to be similar to those of P(sub EFI) and largely to explain them. Finally, we find reasons, based on the similarity of the D(sub RSF) variations to s/l patterns of the average scintillation index, for not using, as is commonly done, such scintillation patterns as substitutes for P(sub EFI) or P(sub inst) patterns.
Document ID
19990062583
Acquisition Source
Headquarters
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
McClure, J. P.
(Texas Univ. at Dallas Richardson, TX United States)
Singh, S.
(Texas Univ. at Dallas Richardson, TX United States)
Bamgboye, D. K.
(Texas Univ. at Dallas Richardson, TX United States)
Johnson, F. S.
(Texas Univ. at Dallas Richardson, TX United States)
Kil, Hyosub
(Texas Univ. at Dallas Richardson, TX United States)
Date Acquired
August 19, 2013
Publication Date
December 1, 1998
Publication Information
Publication: Journal of Geophysical Research
Publisher: American Geophysical Union
Volume: 103
Issue: A12
ISSN: 0148-0227
Subject Category
Geophysics
Report/Patent Number
Paper-98JA02749
Funding Number(s)
CONTRACT_GRANT: NAGw-4002
CONTRACT_GRANT: NAGw-4465
CONTRACT_GRANT: NSF ATM-96-15064
CONTRACT_GRANT: F19628-90-K-0001
Distribution Limits
Public
Copyright
Other

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