Effect of equatorial ionization anomaly on the occurrence of spread-F
The unique geometry of the geomagnetic field lines over the equatorial ionosphere coupled with the E-W electric field causes the equatorial ionization anomaly (EIA) and equatorial spread-F (ESF). Ionosonde data obtained at a chain of four stations covering equator to anomaly crest region (0.3 to...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
1997-02-01
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| Series: | Annales Geophysicae |
| Online Access: | https://www.ann-geophys.net/15/255/1997/angeo-15-255-1997.pdf |
| Summary: | The unique geometry of the geomagnetic field
lines over the equatorial ionosphere coupled with the E-W electric field causes
the equatorial ionization anomaly (EIA) and equatorial spread-F (ESF). Ionosonde
data obtained at a chain of four stations covering equator to anomaly crest
region (0.3 to 33 °N dip) in the Indian sector are used to study the role of
EIA and the associated processes on the occurrence of ESF. The study period
pertains to the equinoctial months (March, April, September and October) of
1991. The ratios of critical frequency of F-layer (<i>ƒ<sub>0</sub></i>F<sub>2</sub>)
and electron densities at an altitude of 270 km between Ahmedabad (33 °N dip)
and Waltair (20 °N dip) are found to shoot up in the afternoon hours on
spread-F days showing strengthening of the EIA in the afternoon hours. The study
confirms the earlier conclusions made by Raghava Rao <i>et al.</i> and Alex <i>et
al.</i> that a well-developed EIA is one of the conditions conducive for the
generation of ESF. This study also shows that the location of the crest is also
important in addition to the strength of the anomaly. |
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| ISSN: | 0992-7689 1432-0576 |