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GEOPHYSICAL RESEARCH LETTERS, VOL. 31, L14805, doi:10.1029/2004GL020031, 2004

Analysis of a mid-latitude E-region LQP event observed during the Coqui 2 Campaign

Julio Urbina

Donaghey College of Information Science and Systems Engineering, University of Arkansas, Little Rock, Arkansas, USA


Erhan Kudeki

Department of Electrical and Computer Engineering, University of Illinois, Urbana, Illinois, USA


Steven J. Franke

Department of Electrical and Computer Engineering, University of Illinois, Urbana, Illinois, USA


Qihou Zhou

Department of Manufacturing and Mechanical Engineering, Miami University, Oxford, Ohio, USA


Abstract

Arecibo ISR observations and VHF coherent backscatter data collected with a radar situated in southern Puerto Rico are examined to understand the causes of quasi-periodic variations in VHF returns from lower E-region heights (∼93 km). It is found that Bragg scale density irregularities causing the observed VHF backscatter are formed and propagated horizontally in a density perturbation field localized at the upper boundary of a tidal ion layer. The density perturbation has a 7 km horizontal wavelength, propagates in southwest direction, and it is not aligned with the geomagnetic field. Thus the production mechanism of the observed density perturbation cannot be the gradient-drift instability often invoked to account for the generation of mid-latitude sporadic E radar echoes. Nevertheless, secondary gradient-drift instability operating on the gradients of the southwest propagating perturbation remains the most likely cause of Bragg scale electron density waves responsible for the VHF returns.

Received 18 March 2004; accepted 24 June 2004; published 31 July 2004.

Index Terms: 2439 Ionosphere: Ionospheric irregularities; 2443 Ionosphere: Midlatitude ionosphere; 2471 Ionosphere: Plasma waves and instabilities; 2487 Ionosphere: Wave propagation (6934).

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Citation: Urbina, J., E. Kudeki, S. J. Franke, and Q. Zhou (2004), Analysis of a mid-latitude E-region LQP event observed during the Coqui 2 Campaign, Geophys. Res. Lett., 31, L14805, doi:10.1029/2004GL020031.