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Nonlinear Evolution Of Mirror Instability In The Earth's Magnetosheath In Pic Simulations, Narges Ahmadihojatabad
Nonlinear Evolution Of Mirror Instability In The Earth's Magnetosheath In Pic Simulations, Narges Ahmadihojatabad
Doctoral Dissertations
Mirror modes are large amplitude non-propagating structures frequently observed in the magnetosheath and they are generated in space plasma environments with proton temperature anisotropy of larger than one. The proton temperature anisotropy also drives the proton cyclotron instability which has larger linear growth rate than that of the mirror instability. Linear dispersion theory predicts that electron temperature anisotropy can enhance the mirror instability growth rate while leaving the proton cyclotron instability largely unaffected. Contrary to the hypothesis, electron temperature anisotropy leads to excitement of the electron whistler instability. Our results show that the electron whistler instability grows much faster than …
"Smoking-Gun" Observables Of Magnetic Reconnection: Spatiotemporal Evolution Of Electron Characteristics Throughout The Diffusion Region, Jason Shuster
Doctoral Dissertations
How does magnetic reconnection happen in a collisionless plasma? Knowledge of electron-scale dynamics is necessary to answer this outstanding question of plasma physics. Based on fully kinetic particle-in-cell (PIC) simulations of symmetric reconnection, the spatiotemporal evolution of velocity distribution functions in and around the electron diffusion region (EDR) elucidates how electrons are accelerated and heated by the cooperating reconnection electric and normal magnetic fields. The discrete, triangular structures characteristic of EDR distributions rotate and gyrotropize in velocity space as electrons remagnetize, forming multicomponent arc and ring structures. Further downstream, exhaust electrons are found to exhibit highly structured, time-dependent anisotropies that …
Quantifying The Role Of The Seed Population In Radiation Belt Dynamics, Alexander Boyd
Quantifying The Role Of The Seed Population In Radiation Belt Dynamics, Alexander Boyd
Doctoral Dissertations
The dynamics of the radiation belts depend on a delicate balance of source and loss processes. One such source process that has been shown to be effective is local acceleration, where 10s-100s keV seed electrons are accelerated via wave-particle interactions up to energies >1 MeV. Historically, much of the focus of radiation belt research has been on the dynamics of these >1 MeV electrons, and the role and importance of the seed electrons has been largely overlooked. In this thesis, we use phase space density calculated using data from the Van Allen Probes, to directly investigate seed population for a …
Analyzing The Interstellar Neutral He Bulk Flow Parameters With Ibex-Lo, Trevor Leonard
Analyzing The Interstellar Neutral He Bulk Flow Parameters With Ibex-Lo, Trevor Leonard
Doctoral Dissertations
Our Sun is immersed in a local galactic environment which is composed of a warm, dilute, and partially ionized gas. Due to the Sun’s motion relative to this environment, the interstellar neutral (ISN) gas flows through the heliosphere providing the opportunity to perform in-situ observations of the ISN gas from Earth’s orbit. The Interstellar Boundary Explorer (IBEX) has observed the ISN gas flow over the past 7 years from a highly elliptical orbit around the Earth. The first observations of ISN H, O, and Ne were recorded by IBEX, along with the most detailed observation of ISN He. Since He …
Small Solar Wind Transients 1995 - 2014: Properties, Modeling, And Effects On The Magnetosphere, Wenyuan Yu
Small Solar Wind Transients 1995 - 2014: Properties, Modeling, And Effects On The Magnetosphere, Wenyuan Yu
Doctoral Dissertations
Using case studies and statistical analysis on a large data sample we investigate properties of small solar wind transients (STs) and discuss their modeling. The observations are from the Wind and STEREO spacecraft. By "small" we mean a duration of 0.5-12 hours. We do not restrict ourselves to magnetic flux ropes. Having arrived at a definition based on an extension of previous work, we apply an automated algorithm to search for STs. In one chapter we focus on the solar activity minimum years 2007-2009. We find an average ST duration of ~4.3 hours, with 75% lasting less than 6 hours. …
Molecular Dynamics Simulations Of A Pentacene Derivative On Gold Surfaces In The Quantum Mechanical And Classical Mechanics Frameworks, Ryan Allen Miller
Molecular Dynamics Simulations Of A Pentacene Derivative On Gold Surfaces In The Quantum Mechanical And Classical Mechanics Frameworks, Ryan Allen Miller
Master's Theses and Capstones
With increasing potential to serve as a basis for constructing organic photovoltaic de- vices, the directed self-assembly of small organic molecules on metal substrates provides an interesting new method of bottom-up device building. By utilizing the qualities inherent in the substrate and molecules, one can manipulate surface topology to create functional layers of molecules in a desired configuration. However, tailoring these organic layers in a useful way requires detailed analysis of the substructure characteristics. With top-down visualization approaches like Scanning Tunneling Microscopy (STM) pro- viding a limited view of assembled layer structural characteristics, molecular dynamics sim- ulations must be employed …