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Title: Association between equatorial and tropical spread-F
Authors: Alex, S
Chandra, H
Rastogi, R G
Issue Date: Apr-2003
Publisher: NISCAIR-CSIR, India
Abstract: Comparative study of spread-F is made from the quarter-hourly ionograms at Huancayo, near the magnetic equator and Bogota, close to the anomaly crest region in the same longitude sector. The occurrence of equatorial spread-F is seen only during nights, preceded by very rapid rise of the F-layer close to the magnetic equator. Based on quarter- hourly ionospheric data at a closely spaced chain of 8 stations in the American sector that operated during IGY, the occurrence of spread-F at low latitudes is shown to be associated with the post-sunset intensification of the ionization anomaly. The ratio of f oF2 at Bogota (anomaly crest) to that at Huancayo (dip equator) shows sudden intensi fication on spread-F days around 1900 hrs LT, peaking between 2000 and 2100 hrs LT and can be used as a precursor to predict sprend -F near the magnetic equator. The onset of spread-F at Bogota, however, requires additional condition of strong spread-F at Huancayo covering a wide range of altitudes and stronger uplift of the F-layer. There are indications that the vertical uplift velocity of F-layer between 1800 and 1900 hrs LT could be used to predict the onset of equatorial spread-F even at crest.
Page(s): 83-92
ISSN: 0975-105X (Online); 0367-8393 (Print)
Appears in Collections:IJRSP Vol.32(2) [April 2003]

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