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Thesis (Ph.D.)--University of Texas at Dallas, 2009. / Includes vita. Includes bibliographical references (leaves140-153)

In this thesis we describe a coupled model of Earth's magnetosphere that consists of the Lyon-Fedder-Mobarry (LFM) global magnetohydrodynamics (MHD) simulation, the MIX ionosphere solver and the Rice Convection Model (RCM). We report some results of the coupled model using idealized inputs and model parameters. The algorithmic and physical components of the model are described, including the transfer of magnetic field information and plasma boundary conditions to the RCM and the return of ring current plasma properties to the LFM. Crucial aspects of the coupling include the restriction of RCM to regions where field-line averaged plasma-beta <=1, the use of a plasmasphere model, and the MIX ionosphere model. Compared to stand-alone MHD, the coupled model produces a substantial increase in ring current pressure and reduction of the magnetic field near the Earth. In the ionosphere, stronger region-1 and region-2 Birkeland currents are seen in the coupled model but with no significant change in the cross polar cap potential drop, while the region-2 currents shielded the low-latitude convection potential. In addition, oscillations in the magnetic field are produced at geosynchronous orbit with the coupled code. The diagnostics of entropy and mass content indicate that these oscillations are associated with low-entropy flow channels moving in from the tail and may be related to bursty bulk flows and bubbles seen in observations. As with most complex numerical models, there is the ongoing challenge of untangling numerical artifacts and physics, and we find that while there is still much room for improvement, the results presented here are encouraging. Finally, we introduce several new methods for magnetospheric visualization and analysis, including a fluid-spatial volume for RCM and a field-aligned analysis mesh for the LFM. The latter allows us to construct novel visualizations of flux tubes, drift surfaces, topological boundaries, and bursty-bulk flows.

Thesis (Ph. D.)--Montana State University--Bozeman, 2007. / Typescript. Chairperson, Graduate Committee: David M. Klumpar. Includes bibliographical references (leaves 102-108).

Earth's plasmasphere persists as an extension of the ionosphere into space. The toroidal region of plasma is shaped by electric and magnetic forces in the terrestrial magnetosphere. As a dense population of cold plasma, the plasmasphere interacts with particles in the hot ring current and energetic radiation belts. Evolution of plasmaspheric density under the driving influence of the solar wind crosses many physical scales. Convective erosion during geomagnetic storms occurs on the order of hours, reducing the size of the plasmasphere by forming an abrupt plasmapause density gradient that varies in radial and diurnal location. The history of geomagntic activity determines the presence of morphological structures as small as notches and as large as plumes. Plasma of atmospheric origin is carried sunward by convection through drainage plumes towards the magnetopause where it can diminish the effectiveness of magnetic reconnection. Long-lived plumes are sustained by a higher rate of refilling than typically observed during plasmasphere recovery from geomagnetic disturbances. The response of the plasmasphere, then, is an integral part of the feedback cycle between the magnetosphere and ionosphere in the exchange of energy and particles. This thesis aims to address three questions concerning the nature of the plasmasphere through the development of empirical and physics-based models under recent observations provided by the Van Allen Probes (RBSP-A & -B). First, what is the distribution of density content in the plasmasphere? For a two year period with full MLT coverage by RBSP, the upper-hybrid resonance frequency in plasma wave spectra is used to identify sudden changes consistent with the plasmapause feature and to calculate the magnetic equatorial electron density. Plasmapause encounter radial locations for both spacecraft are correlated with a geomagnetic activity index showing significant scatter around a linear fit. On average, the predicted plasmapause location does account for the separation between the saturated plasmasphere and the depleted plasmatrough. A density threshold corresponding to the plasmapause boundary is used to sort RBSP measurements into these two classified plasma regions. Model profiles are developed for each region and compared to the results from previous missions. The importance of solar wind properties in regulating the severity of plasmasphere erosion is demonstrated. Second, how does the plasmapause form and vary with geomagnetic activity? The two-dimensional plasmasphere density model, RAM-CPL, is employed to simulate two geomagnetic storms observed by the RBSP spacecraft. Inner-magnetospheric convection is parameterized by the Kp-index and solar wind properties. The performance of RAM-CPL is evaluated by the correspondence between virtual and actual plasmapause encounters. Overall, RAM-CPL achieved good agreement with RBSP observations of the plasmapause to within 0.5 L and measurements of electron density to within one order of magnetude inside the plasmasphere. An empirical model of ring current-ionosphere feedback was included to account for asymmetric erosion, but did not contribute significantly in the MLT sectors of interest when compared to electric field measurements. The difference in background activity level during quiet conditions between the two convection parameterizations was found to lead to 1 L difference in plasmapause location for each simulation trial. Solar wind driven simulations produce sharper and deeper erosion of the plasmapause at the onset of a geomagnetic storm, but also allow for larger recovery of the plasmasphere when compared to Kp-index driven simulations. Third, what is the role of the ionosphere in sustaining the plasmasphere? Four geomagnetic events are observed by RBSP in opposing MLT sectors to exhibit undisturbed plasmasphere refilling following significant erosion of the plasmapause. RAM-CPL simulations of the strongest storm parameterized by solar wind properties shows the full evolution of plasmasphere density from the narrowing of a sunward plume at the onset of erosion, that begins to corotate into a duskside bulge as activity diminishes, to the outward recovery of the plasmapause over several days. A piecewise empirical model of plasmasphere refilling is composed from profiles of equatorial electron density and the observed correlation between the Kp-index and plasmapause location. The RAM-CPL timescale of refilling mediates the increase in density from plasmatrough to plasmasphere levels matching RBSP measurements during the quiet period after the storm. Density observations of the other geomagnetic events are consistent with reports of a two-stage refilling process.

The objective of this dissertation is the development of computer simulation-based models for the modeling of upper ionosphere, starting from the first principles. The models were validated by exact analytical benchmarks and are seen to be consistent with experimentally obtained results. This area of research has significant implications in the area of global communication. In addition, these models would lead to a better understanding of the physical processes taking place in the upper ionosphere.

As humanity continues its expansion into space, the understanding of the near-Earth space environment has never been more critical. As the ionosphere and thermosphere form the boundary between Earth's atmosphere and outer space, characterization of these regions is critical to understanding geospace. The Ionospheric Connection Explorer (ICON), launched in 2019, sought to establish the effects of forcing on the ionosphere and thermosphere from below and above, in part by using observations of ultraviolet airglow, which have long been used as a tool for making remote sensing observations of the upper atmosphere. The Extreme Ultraviolet Spectrometer (EUV) instrument was included on ICON to measure atmospheric airglow between 54 and 88 nm in order to estimate the density and structure of the ionosphere. In this work, we analyze the EUV observations throughout the ICON mission, characterizing the signal observed at various wavelengths during normal operations and during nadir and lunar calibrations. We use the ICON EUV data to develop the first algorithm for retrieval of neutral densities from EUV airglow. / Doctor of Philosophy / As humanity continues its expansion into space, the understanding of the near-Earth space environment has never been more critical. The neutral (thermosphere) and charged (ionosphere) particles in the upper atmosphere, around the altitude where satellite orbit, play a key role as the boundary between Earth and space. The Ionospheric Connection Explorer (ICON), launched in 2019, sought to establish how the ionosphere and thermosphere change over time. It measured the density of particles using light emitted from the atmosphere by chemical reactions (airglow). Extreme Ultraviolet (EUV) light is highly energetic, almost as much as X-rays, and the EUV airglow emitted by the atmosphere at certain can be used to detect O^+. In this work, we examine the measurements from the ICON EUV detector at various wavelengths to determine what other particles can be seen. Notably, we find that the measurements contain information about neutral atomic oxygen and molecular nitrogen. We develop a technique for using the EUV airglow brightness to measure the amount of O and N_2, the first of its kind.

The aim of this diploma thesis was to study the dependence of the intensity of mortality in the Czech Republic, according to the chosen causes of death, on the Solar activity during the increasing and decreasing phase of the Solar cycle in the period 1994-2011, using the methods of the multivariate statistical analysis. The Solar activity was represented by the indices R, Kp, F10.7 and Dst, and also by the height of the F2 layer and TEC for the Czech Republic. The typology of time profiles for causes of death was identified with the help of cluster analysis using time. The dependence between the analyzed time series was investigated using the multivariate statistical analysis. The correlation of the intensity of mortality from coronary heart disease, from stroke, Edwards' and Pataus' syndrom with the Solar activity parameters was discovered, as well as a stronger dependence on the ionosphere parametres related to the Czech Republic area.

Title: Lightning-Related Electromagnetic Wave Phenomena in the Earth's Magnetosphere Author: Jan Záhlava Department: Department of Surface and Plasma Physics Supervisor: doc. RNDr. František Němec, PhD., Department of Surface and Plasma Physics Abstract: The thesis focuses on lightning-related electromagnetic wave phenomena observed by spacecraft in the Earth's inner magnetosphere. Two different approaches are used to identify the frequency and spatial extent where lightning generated emissions significantly contribute to the overall wave intensity. First, whistler detections onboard the DEMETER spacecraft are used to sort the measurements according to the whistler activity. Second, we use a geographic distribution of lightning activity and analyze a dependence of the overall wave intensity on geomagnetic longitude. We show that, especially during the night, the overall wave intensity observed in the plasmasphere is well correlated with lightning activity. The other focus of the study is on special electromagnetic wave events consisting of alternating frequency bands of enhanced and reduced wave intensity formed in the ionosphere due to lightning. We analyze their occurrence and parameters, and we suggest a possible mechanism of their formation. Keywords: lightning, waves in plasma, whistlers, plasmasphere

Title: Lightning-Related Electromagnetic Wave Phenomena in the Earth's Magnetosphere Author: Jan Záhlava Department: Department of Surface and Plasma Physics Supervisor: doc. RNDr. František Němec, PhD., Department of Surface and Plasma Physics Abstract: The thesis focuses on lightning-related electromagnetic wave phenomena observed by spacecraft in the Earth's inner magnetosphere. Two different approaches are used to identify the frequency and spatial extent where lightning generated emissions significantly contribute to the overall wave intensity. First, whistler detections onboard the DEMETER spacecraft are used to sort the measurements according to the whistler activity. Second, we use a geographic distribution of lightning activity and analyze a dependence of the overall wave intensity on geomagnetic longitude. We show that, especially during the night, the overall wave intensity observed in the plasmasphere is well correlated with lightning activity. The other focus of the study is on special electromagnetic wave events consisting of alternating frequency bands of enhanced and reduced wave intensity formed in the ionosphere due to lightning. We analyze their occurrence and parameters, and we suggest a possible mechanism of their formation. Keywords: lightning, waves in plasma, whistlers, plasmasphere