Browsing by Author "Bhattacharyya, S."

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    A new approach in incoherent scatter F region E x B drift measurements at Jicamarca
    (American Geophysical Union, 1999-12-01) Kudeki, E.; Bhattacharyya, S.; Woodman Pollitt, Ronald Francisco
    Since 1996 incoherent scatter F region plasma drift measurements at Jicamarca have been implemented using a new signal processing approach replacing the traditional pulse-to-pulse correlation method. The new method, based on Doppler spectrum estimation and nonlinear least squares fitting to model spectra obtained from incoherent scatter theory, improves the instrumental sensitivity remarkably under low signal-to-noise conditions. With the new method it has become possible to obtain very high quality drifts data at nearly all hours of the day throughout most F region heights. Altitudinal smoothing of the drifts data to reduce measurement noise is no longer necessary, and studies of the height variations of drifts can be performed with much greater certainty than before. Small-amplitude gravity wave oscillations have been detected at F region heights and a vortical circulation of the F region plasma has been observed in the post sunset period.
    Palabras clave:F RegionPlasmaSpectral analysis
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    Postsunset vortex in equatorial F-region plasma drifts and implications for bottomside spread-F
    (American Geophysical Union, 1999-12-01) Kudeki, E.; Bhattacharyya, S.
    Recent high‐resolution incoherent scatter drift measurements conducted at Jicamarca during solar minimum conditions indicate that a vortical plasma flow pattern accompanies the well known prereversal enhancement events observed in the equatorial F region. The vortex is centered at ∼250 km altitude and about 2000–3000 km east of the evening terminator and is characterized by upward and downward flows to the west and to the east and eastward and westward flows on the top and the bottom, respectively. Postsunset bottomside spread‐F events are observed to commence in the interior of the vortex in regions of westward plasma drifts. The formation of the vortex implies localized charging of the postsunset bottomside F region in response to eastward neutral wind driven F region dynamo action.
    Palabras clave:Coherent scatteringF regionNeutral wind