Date of Award:

5-2015

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Physics

Committee Chair(s)

Ludger Scherliess

Committee

Ludger Scherliess

Committee

Robert Schunk

Committee

Bela Fejer

Committee

Michael Taylor

Committee

Charles Swenson

Abstract

The Earth's ionosphere, which is the ionized part of the upper atmosphere, plays a very important role in ground- and satellite-based radio communication and navigation. During the last half century, a considerable experimental, theoretical, and modeling effort has been directed towards understanding the physical processes that affect the variation of the ionization in the ionosphere at various spatial and temporal scales. Even though tremendous progress has been made in many directions of ionospheric research, many questions remain to be answered.

One of the intriguing features in the ionosphere is an anomalous evening enhancement that occurs over certain mid-latitude locations, where the ionization may become more than twice as large during the evening/night hours than during noon. The phenomenon takes place during summer and is most prominent over a region west of the Antarctic Peninsula where it is known as the Weddell Sea Anomaly. The generation mechanisms of this anomaly are still being debated and its accurate modeling remains a challenge.

In this dissertation, the physical mechanisms behind this evening anomaly are investigated with an emphasis on the role of winds in its generation. For this, data assimilation techniques were used for the first time to estimate the global wind velocities. These winds were then used together with a physics-based model of the ionosphere to establish the relative importance of plasma production, recombination, and transport processes in the generation of the evening anomaly.

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Included in

Physics Commons

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