Date of Award

Spring 1-1-2017

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

First Advisor

Jeffrey Thayer

Second Advisor

Wiebke Deierling

Third Advisor

Jeffrey Forbes

Fourth Advisor

Robert Marshall

Fifth Advisor

Katja Friedrich

Abstract

The underlying physics and dynamics of the atmosphere drive electric currents and establish electric fields in a phenomenon known as the global electric circuit (GEC). The GEC has been observed and modeled with limiting assumptions and parameterizations in previous research. This thesis describes the incorporation of a physics-based GEC modeling scheme into a sophisticated climate model to describe the evolution of GEC currents, ground-ionosphere potential, electric fields, and conductivity within the atmosphere. Supporting measurements of atmospheric electric fields over time were used to describe the impact of local meteorological changes and assess the GEC contribution to near-surface electric fields.

The source currents within the GEC are generated by a global distribution of electrified clouds. The produced currents lead to a potential difference between the ground and ionosphere. This potential difference produces return currents that are dependent on the global conductivity distribution. Realistic physics and dynamics produced within the climate model are used to generate the conductivity of the atmosphere. The conductivity calculation includes a 3-D spatial and temporal determination of ion production from radon, galactic cosmic rays, and solar proton events and ion losses from recombination, clouds, and aerosols. To validate the model, several data sets from Antarctica and an array of measurements from Kennedy Space Center were utilized. The use of these data sets required new statistical methods to be developed to better understand how local meteorological processes affect electric fields including the wind direction, clouds, and the local sunrise.

Coupling the conductivity and sources together within the model produces new insights into the GEC efficiency of electrical storms. Storms near the equator tend to be strong but inefficient, while storms at mid-latitude are weaker and more efficient. This leads to the global source current distribution shifting more poleward. The model is also used to simulate changes in the GEC caused by volcanic eruptions and the solar cycle. Although the GEC is global in nature, diurnal, seasonal, and annual variations in electric field measurements from the model are highly location dependent.

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