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| Titel |
Solar flux dependence of coherence scales in scintillation patterns produced by ESF irregularities |
| VerfasserIn |
B. Engavale, K. Jeeva, K. U. Nair, A. Bhattacharyya |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
0992-7689
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| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 23, no. 10 ; Nr. 23, no. 10 (2005-11-30), S.3261-3266 |
| Datensatznummer |
250015397
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| Publikation (Nr.) |
 copernicus.org/angeo-23-3261-2005.pdf |
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| Zusammenfassung |
| The coherence scale length, defined as the 50% decorrelation
scale length along the magnetic east-west direction, in the ground
scintillation pattern obtained at a dip equatorial location, due
to scattering of VHF radio waves by equatorial spread F (ESF)
irregularities, is calculated, using amplitude scintillation data
recorded by two spaced receivers. The average east-west drift of
the ground scintillation pattern, during the pre- and post-midnight
periods, also calculated from the same observations, shows an
almost linear increase with 10.7-cm solar flux. In the present
paper the variability of the drift is automatically taken into
account in the calculation of the coherence scale length of the
ground scintillation pattern. For weak scintillations, the
coherence scale depends on the Fresnel scale, which varies with
the height of the irregularity layer, and also on the spectral
index of the irregularity power spectrum. It is found that for
weak scintillations, the coherence scales are much better
organized according to the 10.7-cm solar flux, during the
pre-midnight period, than during the post-midnight period, with a
general trend of coherence scale length increasing with 10.7-cm
solar flux except for cases with F 10.7-cm solar flux <100.
This indicates that, during the initial phase of ESF irregularity
development, the irregularity spectrum does not have much variability
while further evolution of the spatial structure in ESF
irregularities is controlled by factors other than the solar flux. |
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