Please use this identifier to cite or link to this item: http://hdl.handle.net/2248/3184
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dc.contributor.authorSastri, J. H-
dc.date.accessioned2008-08-18T11:06:03Z-
dc.date.available2008-08-18T11:06:03Z-
dc.date.issued1998-03-
dc.identifier.citationJournal of Geophysical Research, Vol. 103, No. A3, pp. 3983 - 3991en
dc.identifier.issn0148-0227-
dc.identifier.urihttp://hdl.handle.net/2248/3184-
dc.descriptionOpen Access-
dc.description.abstractThe regular postsunset enhancement of upward drift of the equatorial F region is observed to be abnormally large on certain quiet days (Ap ≤ 5) as manifested by an anomalous dusktime increase of F region height. We explored the origin of this extreme form of the quiet-time variability of postsunset vertical drift/height through case studies using data from the ionosonde and magnetometer networks in the Indian equatorial region. It is found that on the days with an unsually large postsunset increase of F region height near the magnetic equator, the diurnal profile of the equatorial electrojet (EEJ) strength is severly distorted (with a shift, in some cases, of Sq(H) phase from the usual time interval, charactersitic of the abnormal quiet days) with enhanced EEJ conditions in the postnoon period (1300–1600 LT). This is accompanied, near the magnetic equator, by higher values of F layer peak height (hpF2) and lower values of peak electron density (ƒ0F2) in the early evening period (1600–1800 LT), compared with the monthly median/quiet day mean values. These changes in EEJ and hpF2/ƒ0F2 are consistently seen in all eight cases studied. It is suggested that the perturbations in plasma density distribution of equatorial F region increase the therinospheric zonal wind and its local time gradient and the ratio of flux-tube-integrated Pedersen conductivity of the F to E region. These modifications just prior to sunset of the properties of the equatorial thermosphere-ionosphere prompt an efficient F region dynamo action, resulting in the observed abnormally large dusktime increase of F region height.en
dc.format.extent3894 bytes-
dc.format.mimetypeapplication/pdf-
dc.language.isoenen
dc.publisherAmerican Geophysical Unionen
dc.relation.urihttp://www.agu.org/pubs/crossref/1998/97JA02649.shtmlen
dc.subject2415 Ionosphereen
dc.subjectEquatorial Ionosphereen
dc.subject2427 Ionosphere/Atmosphere Interactions (0335)en
dc.subject2467 Plasma Temperature and Densityen
dc.subject3369 Meteorology And Atmospheric Dynamicsen
dc.subjectThermospheric Dynamics (0358)en
dc.titleOn the development of abnormally large postsunset upward drift of equatorial F region under quiet geomagnetic conditionsen
dc.typeArticleen
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