Date of Award:

5-2016

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Electrical and Computer Engineering

Committee Chair(s)

Charles Swenson

Committee

Charles Swenson

Committee

Jan Sojka

Committee

Robert Schunk

Committee

Todd Moon

Committee

Jacob Gunther

Abstract

The terrestrial atmospheric region between the altitudes of 90 km and 600 km is known as the thermosphere region. The thermosphere is continuously modulated by particle emissions and magnetic fields that originate from the sun. These fields and emissions are intensified during events known as geomagnetic storms which alter the state of the thermosphere by dumping gigawatts of energy. This energy is mostly deposited in the lower thermosphere regions of 150 km and below and can potentially have hazardous repercussions on the technological assets of mankind. These storms can disrupt radio communication systems, interrupt electric power systems, threaten the safety of astronauts, and disrupt global position systems (GPS), all of which can wreck havoc on the technology-dependent human society. Hence it is essential that we understand and predict the influence of these storms on the terrestrial thermosphere.

Our current understanding of the thermospheric response to the geomagnetic storm energy is limited to observations of the thermospheric state at orbital altitudes of 400 km and above. The state of the thermosphere at altitudes of 150 km and below during geomagnetic storms is largely unknown. This lower thermospheric response is instrumental in understanding and predicting the thermospheric state during geomagnetic storms. In this dissertation we bridge the gap in understanding the thermospheric response to storms by observing the change in lower thermospheric state in the event of geomagnetic storm occurrences.

We conduct this study using kinetic temperatures obtained from the SABER (Sounding of the Atmosphere Using Broadband Emission Radiometry) instrument onboard the TIMED (Thermosphere, Ionosphere, and Mesosphere Energy Dynamics) satellite. We conduct a statistical study of storms corresponding to a decade worth of data to find out the magnitude and time scales of the geomagnetic storm induced changes of the lower thermospheric state. We use methods of inferential and descriptive statistics to investigate the storm induced global changes for more than a hundred storms that occurred between 2002 and 2010. We also investigate the performance of the state-of-art physics and empirical models in predicting the lower thermospheric state during geomagnetic storms.

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