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University of Iowa

1. De Pascuale, Sebastian. The plasmasphere extension of Earth's atmosphere: a perspective from the Van Allen probes.

Degree: PhD, Physics, 2018, University of Iowa

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… Advisors/Committee Members: Kletzing, Craig A. (supervisor).

Subjects/Keywords: Ionosphere; Magnetosphere; Plasmapause; Plasmasphere; RBSP; Van Allen Probes; Physics

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APA (6th Edition):

De Pascuale, S. (2018). The plasmasphere extension of Earth's atmosphere: a perspective from the Van Allen probes. (Doctoral Dissertation). University of Iowa. Retrieved from https://ir.uiowa.edu/etd/6405

Chicago Manual of Style (16th Edition):

De Pascuale, Sebastian. “The plasmasphere extension of Earth's atmosphere: a perspective from the Van Allen probes.” 2018. Doctoral Dissertation, University of Iowa. Accessed January 18, 2021. https://ir.uiowa.edu/etd/6405.

MLA Handbook (7th Edition):

De Pascuale, Sebastian. “The plasmasphere extension of Earth's atmosphere: a perspective from the Van Allen probes.” 2018. Web. 18 Jan 2021.

Vancouver:

De Pascuale S. The plasmasphere extension of Earth's atmosphere: a perspective from the Van Allen probes. [Internet] [Doctoral dissertation]. University of Iowa; 2018. [cited 2021 Jan 18]. Available from: https://ir.uiowa.edu/etd/6405.

Council of Science Editors:

De Pascuale S. The plasmasphere extension of Earth's atmosphere: a perspective from the Van Allen probes. [Doctoral Dissertation]. University of Iowa; 2018. Available from: https://ir.uiowa.edu/etd/6405


University of Iowa

2. Mokrzycki, Brian Thomas. WvFEv3, An FPGA-based general purpose digital signal processor for space applications.

Degree: MS, Electrical and Computer Engineering, 2011, University of Iowa

The Waves instruments aboard the Juno and Radiation Belt Storm Probe (RBSP) spacecraft represents the next generation of space radio and plasma wave instrumentation developed by the University of Iowa's Radio and Plasma Wave group. The previous generation of such instruments on the Cassini spacecraft utilized several analog signal-conditioning techniques to compress and condense scientific data. Compression techniques are necessary because the plasma wave instruments can often generate significantly more science data than can be transmitted using the narrow telemetry channel of the hosting spacecraft. The next generation of plasma wave instrumentation represents a major shift of analog signal conditioning functionality to the digital domain, drastically reducing the amount of power and mass required by the instrument while simultaneously further condensing scientific data, increasing the precision of plasma emission measurements, and adding flexibility. The solution presented in this thesis is to utilize a low-cost radiation tolerant field programmable gate array (FPGA) that serves as a space qualified implementation platform for a custom designed general-purpose digital signal processor, called the WvFEv3. Advisors/Committee Members: Casavant, Thomas L. (supervisor).

Subjects/Keywords: computer architecture; DSP; FPGA; Juno; processor design; RBSP; Electrical and Computer Engineering

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Mokrzycki, B. T. (2011). WvFEv3, An FPGA-based general purpose digital signal processor for space applications. (Masters Thesis). University of Iowa. Retrieved from https://ir.uiowa.edu/etd/3355

Chicago Manual of Style (16th Edition):

Mokrzycki, Brian Thomas. “WvFEv3, An FPGA-based general purpose digital signal processor for space applications.” 2011. Masters Thesis, University of Iowa. Accessed January 18, 2021. https://ir.uiowa.edu/etd/3355.

MLA Handbook (7th Edition):

Mokrzycki, Brian Thomas. “WvFEv3, An FPGA-based general purpose digital signal processor for space applications.” 2011. Web. 18 Jan 2021.

Vancouver:

Mokrzycki BT. WvFEv3, An FPGA-based general purpose digital signal processor for space applications. [Internet] [Masters thesis]. University of Iowa; 2011. [cited 2021 Jan 18]. Available from: https://ir.uiowa.edu/etd/3355.

Council of Science Editors:

Mokrzycki BT. WvFEv3, An FPGA-based general purpose digital signal processor for space applications. [Masters Thesis]. University of Iowa; 2011. Available from: https://ir.uiowa.edu/etd/3355


University of Colorado

3. Ali, Ashar Fawad. ULF Waves and Diffusive Radial Transport of Charged Particles.

Degree: PhD, Applied Mathematics, 2016, University of Colorado

The Van Allen radiation belts contain highly energetic particles which interact with a variety of plasma and magnetohydrodynamic (MHD) waves. Waves in the ultra low-frequency (ULF) range play an important role in the loss and acceleration of energetic particles. Considering the geometry of the geomagnetic field, charged particles trapped in the inner magnetosphere undergo three distinct types of periodic motions; an adiabatic invariant is associated with each type of motion. The evolution of the phase space density of charged particles in the magnetosphere in the coordinate space of the three adiabatic invariants is modeled by the Fokker-Planck equation. If we assume that the first two adiabatic invariants are conserved while the third invariant is violated, then the general Fokker-Planck equation reduces to a radial diffusion equation with the radial diffusion coefficient quantifying the rate of the radial diffusion of charged particles, including contributions from perturbations in both the magnetic and the electric fields. This thesis investigates two unanswered questions about ULF wave-driven radial transport of charged particles. First, how important are the ULF fluctuations in the magnetic field compared with the ULF fluctuations in the electric field in driving the radial diffusion of charged particles in the Earth's inner magnetosphere? It has generally been accepted that magnetic field perturbations dominate over electric field perturbations, but several recently published studies suggest otherwise. Second, what is the distribution of ULF wave power in azimuth, and how does ULF wave power depend upon radial distance and the level of geomagnetic activity? Analytic treatments of the diffusion coefficients generally assume uniform distribution of power in azimuth, but in situ measurements suggest that this may not be the case. We used the magnetic field data from the Combined Release and Radiation Effects Satellite (CRRES) and the electric and the magnetic field data from the Radiation Belt Storm Probes (RBSP) to compute the electric and the magnetic component of the radial diffusion coefficient using the Fei et al. [2006] formulation. We conclude that contrary to prior notions, the electric component is dominant in driving radial diffusion of charged particles in the Earth's inner magnetosphere instead of the magnetic component. The electric component can be up to two orders of magnitude larger than the magnetic component. In addition, we see that ULF wave power in both the electric and the magnetic fields has a clear dependence on Kp with wave power decreasing as radial distance decreases. For both fields, the noon sectors generally contain more ULF wave power than the dawn, dusk, and the midnight magnetic local time (MLT) sectors. There is no significant difference between ULF wave power in the dawn, dusk, and the midnight sectors. Advisors/Committee Members: Scot R. Elkington, Jem Corcoran, Howard Singer, Juan Restrepo, William Kleiber.

Subjects/Keywords: CRRES; Magnetospheric Physics; Radial Diffusion; RBSP; ULF Waves; Van Allen Radiation Belts; Applied Mathematics; Plasma and Beam Physics

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Ali, A. F. (2016). ULF Waves and Diffusive Radial Transport of Charged Particles. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/appm_gradetds/71

Chicago Manual of Style (16th Edition):

Ali, Ashar Fawad. “ULF Waves and Diffusive Radial Transport of Charged Particles.” 2016. Doctoral Dissertation, University of Colorado. Accessed January 18, 2021. https://scholar.colorado.edu/appm_gradetds/71.

MLA Handbook (7th Edition):

Ali, Ashar Fawad. “ULF Waves and Diffusive Radial Transport of Charged Particles.” 2016. Web. 18 Jan 2021.

Vancouver:

Ali AF. ULF Waves and Diffusive Radial Transport of Charged Particles. [Internet] [Doctoral dissertation]. University of Colorado; 2016. [cited 2021 Jan 18]. Available from: https://scholar.colorado.edu/appm_gradetds/71.

Council of Science Editors:

Ali AF. ULF Waves and Diffusive Radial Transport of Charged Particles. [Doctoral Dissertation]. University of Colorado; 2016. Available from: https://scholar.colorado.edu/appm_gradetds/71

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