Open Access. Powered by Scholars. Published by Universities.®

Physics Commons

Open Access. Powered by Scholars. Published by Universities.®

Articles 1 - 30 of 160

Full-Text Articles in Physics

2d Ion Temperature Maps From Twins Ena Data: Idl Scripts, Amy Keesee, Earl Scime, Anna Zaniewski, Roxanne Katus Jan 2019

2d Ion Temperature Maps From Twins Ena Data: Idl Scripts, Amy Keesee, Earl Scime, Anna Zaniewski, Roxanne Katus

Physics Scholarship

Energetic neutral atom (ENA) flux from the NASA TWINS mission (and previously the MENA instrument on the NASA IMAGE mission) is projected along the line of sight to the equatorial plane in GSM coordinates. A Maxwellian fit is used to calculate the ion temperature in each equatorial plane bin, creating 2D maps of ion temperatures. The files are IDL .pro scripts that can be read using a text editor. IDL software is required to run. The primary script is twins_master.pro. The scripts call other scripts that were developed by the TWINS mission team as well as publicly available IDL ...


Review Of Solid Polarized Targets, Leiqaa Kurbany May 2018

Review Of Solid Polarized Targets, Leiqaa Kurbany

Student Research Projects

In the following pages I review polarized solid-state target briefly. What I discovered through my reading and writing about this technology, that is amazing tool to study the nucleon structure. I started with what is polarized solid-state target, went through Dynamic Nuclear Polarization (DNP) to understanding how it works, then its setup, in what experiments they used polarized solid-state target and some results of these experiments and finally I wrote a brief definition to many of terms, they are important to know to understand what is polarized solid state target.


Disorder Influences The Quantum Critical Transport At A Superconductor-To-Insulator Transition, H Q. Nguyen, Shawna M. Hollen, J M. Valles Jr., J Shainline, J. M. Xu Oct 2015

Disorder Influences The Quantum Critical Transport At A Superconductor-To-Insulator Transition, H Q. Nguyen, Shawna M. Hollen, J M. Valles Jr., J Shainline, J. M. Xu

Physics Scholarship

We isolated flux disorder effects on the transport at the critical point of the quantum magnetic field tuned superconductor-to-insulator transition (BSIT). The experiments employed films patterned into geometrically disordered hexagonal arrays. Spatial variations in the flux per unit cell, which grow in a perpendicular magnetic field, constitute flux disorder. The growth of flux disorder with magnetic field limited the number of BSITs exhibited by a single film due to flux matching effects. The critical metallic resistance at successive BSITs grew with flux disorder contrary to predictions of its universality. These results open the door for controlled studies of disorder effects ...


Modification Of Electronic Surface States By Graphene Islands On Cu(111), Shawna M. Hollen, G A. Gambrel, S J. Tjung, N M. Santagata, Ezekiel Johnston-Halperin, Jay A. Gupta May 2015

Modification Of Electronic Surface States By Graphene Islands On Cu(111), Shawna M. Hollen, G A. Gambrel, S J. Tjung, N M. Santagata, Ezekiel Johnston-Halperin, Jay A. Gupta

Physics Scholarship

We present a study of graphene/substrate interactions on ultrahigh-vacuum-grown graphene islands with minimal surface contamination using in situ low-temperature scanning tunneling microscopy. We compare the physical and electronic structure of the sample surface with atomic spatial resolution on graphene islands versus regions of bare Cu(111) substrate. We find that the Rydberg-like series of image potential states is shifted toward lower energy over the graphene islands relative to Cu(111), indicating a decrease in the local work function, and the resonances have a much smaller linewidth, indicating reduced coupling to the bulk. In addition, we show the dispersion of ...


Scanning Tunneling Microscopy Studies Of Graphene And Hydrogenated Graphene On Cu, Shawna M. Hollen, G A. Gambrel, S J. Tjung, N M. Santagata, Ezekiel Johnston-Halperin, Jay A. Gupta Mar 2015

Scanning Tunneling Microscopy Studies Of Graphene And Hydrogenated Graphene On Cu, Shawna M. Hollen, G A. Gambrel, S J. Tjung, N M. Santagata, Ezekiel Johnston-Halperin, Jay A. Gupta

Physics Scholarship

Because of the innate sensitivity of 2D material surfaces, it is increasingly important to understand and characterize surface functionalization and interactions with environmental elements, such as substrate, metallic contacts, and adatoms. We developed a method for reproducible, epitaxial growth of pristine graphene islands on Cu(111) in UHV and use scanning tunneling microscopy and spectroscopy (STM) to study the interaction of these graphene islands with the Cu substrate. Tunneling spectroscopy measurements of the electronic surface states over the graphene islands indicate a lower local work function, decreased coupling to bulk Cu states, and a decreased electron effective mass. Additionally, we ...


Transport In Thin Insulating Films Close To The Boson-Fermion Crossover, J C. Joy, X Zhang, Shawna M. Hollen, C Zhao, G. E. Fernandes, J. M. Xu, J M. Valles Jr. Mar 2015

Transport In Thin Insulating Films Close To The Boson-Fermion Crossover, J C. Joy, X Zhang, Shawna M. Hollen, C Zhao, G. E. Fernandes, J. M. Xu, J M. Valles Jr.

Physics Scholarship

No abstract provided.


Investigation Of Emic Wave Scattering As The Cause For The Barrel 17 January 2013 Relativistic Electron Precipitation Event: A Quantitative Comparison Of Simulation With Observations, Zan Li, Robyn M. Millan, Mary K. Hudson, Leslie A. Woodger, David M. Smith, Yue Chen, R. Friedel, J. V. Rodriguez, Mark J. Engebretson, J. Goldstein, Joseph F. Fennell, Harlan E. Spence Dec 2014

Investigation Of Emic Wave Scattering As The Cause For The Barrel 17 January 2013 Relativistic Electron Precipitation Event: A Quantitative Comparison Of Simulation With Observations, Zan Li, Robyn M. Millan, Mary K. Hudson, Leslie A. Woodger, David M. Smith, Yue Chen, R. Friedel, J. V. Rodriguez, Mark J. Engebretson, J. Goldstein, Joseph F. Fennell, Harlan E. Spence

Physics Scholarship

Abstract

Electromagnetic ion cyclotron (EMIC) waves were observed at multiple observatory locations for several hours on 17 January 2013. During the wave activity period, a duskside relativistic electron precipitation (REP) event was observed by one of the Balloon Array for Radiation belt Relativistic Electron Losses (BARREL) balloons and was magnetically mapped close to Geostationary Operational Environmental Satellite (GOES) 13. We simulate the relativistic electron pitch angle diffusion caused by gyroresonant interactions with EMIC waves using wave and particle data measured by multiple instruments on board GOES 13 and the Van Allen Probes. We show that the count rate, the energy ...


Quantifying The Relative Contributions Of Substorm Injections And Chorus Waves To The Rapid Outward Extension Of Electron Radiation Belt, Q. Zong, C A. Kletzing, W. S. Kurth, G. B. Hospodarsky, Harlan E. Spence, Geoffrey Reeves, H. O. Funsten, J. B. Blake, D. N. Baker Dec 2014

Quantifying The Relative Contributions Of Substorm Injections And Chorus Waves To The Rapid Outward Extension Of Electron Radiation Belt, Q. Zong, C A. Kletzing, W. S. Kurth, G. B. Hospodarsky, Harlan E. Spence, Geoffrey Reeves, H. O. Funsten, J. B. Blake, D. N. Baker

Physics Scholarship

Abstract

We study the rapid outward extension of the electron radiation belt on a timescale of several hours during three events observed by Radiation Belt Storm Probes and Time History of Events and Macroscale Interactions during Substorms satellites and particularly quantify the contributions of substorm injections and chorus waves to the electron flux enhancement near the outer boundary of radiation belt. A comprehensive analysis including both observations and simulations is performed for the first event on 26 May 2013. The outer boundary of electron radiation belt moved from L = 5.5 to L > 6.07 over about 6 h, with ...


Does The Worsening Galactic Cosmic Radiation Environment Observed By Crater Preclude Future Manned Deep Space Exploration?, Nathan A. Schwadron, J. B. Blake, Anthony Case, Colin J. Joyce, Justin Kasper, J. E. Mazur, N. Petro, M. Quinn, Jamie A. Porter, Charles W. Smith, Sonya S. Smith, Harlan E. Spence, Lawrence W. Townsend, R. Turner, Jody K. Wilson, Cary Zeitlin Nov 2014

Does The Worsening Galactic Cosmic Radiation Environment Observed By Crater Preclude Future Manned Deep Space Exploration?, Nathan A. Schwadron, J. B. Blake, Anthony Case, Colin J. Joyce, Justin Kasper, J. E. Mazur, N. Petro, M. Quinn, Jamie A. Porter, Charles W. Smith, Sonya S. Smith, Harlan E. Spence, Lawrence W. Townsend, R. Turner, Jody K. Wilson, Cary Zeitlin

Physics Scholarship

Abstract

The Sun and its solar wind are currently exhibiting extremely low densities and magnetic field strengths, representing states that have never been observed during the space age. The highly abnormal solar activity between cycles 23 and 24 has caused the longest solar minimum in over 80 years and continues into the unusually small solar maximum of cycle 24. As a result of the remarkably weak solar activity, we have also observed the highest fluxes of galactic cosmic rays in the space age and relatively small solar energetic particle events. We use observations from the Cosmic Ray Telescope for the ...


Excitation Of Nightside Magnetosonic Waves Observedby Van Allen Probes, Qinghua Zhou, Fuliang Xiao, Chang Yang, Si Liu, C A. Kletzing, W. S. Kurth, G. B. Hospodarsky, Harlan E. Spence, Geoffrey Reeves, H. O. Funsten, J. B. Blake, D. N. Baker, J. R. Wygant Nov 2014

Excitation Of Nightside Magnetosonic Waves Observedby Van Allen Probes, Qinghua Zhou, Fuliang Xiao, Chang Yang, Si Liu, C A. Kletzing, W. S. Kurth, G. B. Hospodarsky, Harlan E. Spence, Geoffrey Reeves, H. O. Funsten, J. B. Blake, D. N. Baker, J. R. Wygant

Physics Scholarship

Abstract

During the recovery phase of the geomagnetic storm on 30-31 March 2013, Van Allen Probe A detected enhanced magnetosonic (MS) waves in a broad range of L = 1.8-4.7 and magnetic local time (MLT) = 17-22 h, with a frequency range ∼10-100 Hz. In the meanwhile, distinct proton ring distributions with peaks at energies of ∼10 keV, were also observed in L = 3.2-4.6 and L = 5.0-5.6. Using a subtracted bi-Maxwellian distribution to model the observed proton ring distribution, we perform three-dimensional ray tracing to investigate the instability, propagation, and spatial distribution of MS waves. Numerical ...


Fate Of The Bose Insulator In The Limit Of Strong Localization And Low Cooper-Pair Density In Ultrathin Films, Shawna M. Hollen, G. E. Fernandes, J. M. Xu, J M. Valles Jr. Oct 2014

Fate Of The Bose Insulator In The Limit Of Strong Localization And Low Cooper-Pair Density In Ultrathin Films, Shawna M. Hollen, G. E. Fernandes, J. M. Xu, J M. Valles Jr.

Physics Scholarship

A Bose insulator composed of a low density of strongly localized Cooper pairs develops at the two-dimensional superconductor to insulator transition (SIT) in a number of thin film systems. Investigations of ultrathin amorphous PbBi films far from the SIT described here provide evidence that the Bose insulator gives way to a second insulating phase with decreasing film thickness. At a critical film thickness dc the magnetoresistance changes sign from positive, as expected for boson transport, to negative, as expected for fermion transport, signs of local Cooper-pair phase coherence effects on transport vanish, and the transport activation energy exhibits a kink ...


Interactions Of Energetic Electrons With Ulf Waves Triggered By Interplanetary Shock: Van Allen Probes Observations In The Magnetotail, Y. X. Hao, Q. G. Zong, Y. F. Wang, X. Z. Zhou, Hui Zhang, S. Y. Fu, Z. Y. Pu, Harlan E. Spence, J. B. Blake, J. Bonnell, J. R. Wygant, C A. Kletzing Oct 2014

Interactions Of Energetic Electrons With Ulf Waves Triggered By Interplanetary Shock: Van Allen Probes Observations In The Magnetotail, Y. X. Hao, Q. G. Zong, Y. F. Wang, X. Z. Zhou, Hui Zhang, S. Y. Fu, Z. Y. Pu, Harlan E. Spence, J. B. Blake, J. Bonnell, J. R. Wygant, C A. Kletzing

Physics Scholarship

Abstract

We present in situ observations of a shock-induced substorm-like event on 13 April 2013 observed by the newly launched Van Allen twin probes. Substorm-like electron injections with energy of 30-500 keV were observed in the region from L∼5.2 to 5.5 immediately after the shock arrival (followed by energetic electron drift echoes). Meanwhile, the electron flux was clearly and strongly varying on the ULF wave time scale. It is found that both toroidal and poloidal mode ULF waves with a period of 150 s emerged following the magnetotail magnetic field reconfiguration after the interplanetary (IP) shock passage ...


The Trapping Of Equatorial Magnetosonic Waves In The Earth’S Outer Plasmasphere, Q. Ma, W Li, L. Chen, R. M. Thorne, C A. Kletzing, W. S. Kurth, G. B. Hospodarsky, Geoffrey Reeves, M. G. Henderson, Harlan E. Spence Sep 2014

The Trapping Of Equatorial Magnetosonic Waves In The Earth’S Outer Plasmasphere, Q. Ma, W Li, L. Chen, R. M. Thorne, C A. Kletzing, W. S. Kurth, G. B. Hospodarsky, Geoffrey Reeves, M. G. Henderson, Harlan E. Spence

Physics Scholarship

Abstract

We investigate the excitation and propagation of equatorial magnetosonic waves observed by the Van Allen Probes and describe evidence for a trapping mechanism for magnetosonic waves in the Earth's plasmasphere. Intense equatorial magnetosonic waves were observed inside the plasmasphere in association with a pronounced proton ring distribution, which provides free energy for wave excitation. Instability analysis along the inbound orbit demonstrates that broadband magnetosonic waves can be excited over a localized spatial region near the plasmapause. The waves can subsequently propagate into the inner plasmasphere and remain trapped over a limited radial extent, consistent with the predictions of ...


Deep Dielectric Charging Of Regolith Within The Moon's Permanently Shadowed Regions, Andrew P. Jordan, T. J. Stubbs, Jody K. Wilson, Nathan A. Schwadron, Harlan E. Spence, Colin J. Joyce Aug 2014

Deep Dielectric Charging Of Regolith Within The Moon's Permanently Shadowed Regions, Andrew P. Jordan, T. J. Stubbs, Jody K. Wilson, Nathan A. Schwadron, Harlan E. Spence, Colin J. Joyce

Physics Scholarship

Abstract

Energetic charged particles, such as galactic cosmic rays (GCRs) and solar energetic particles (SEPs), can penetrate deep within the lunar surface, resulting in deep dielectric charging. This charging process depends on the GCR and SEP currents, as well as on the regolith's electrical conductivity and permittivity. In permanently shadowed regions (PSRs) near the lunar poles, the discharging timescales are on the order of a lunation (∼20 days). We present the first predictions for deep dielectric charging of lunar regolith. To estimate the resulting subsurface electric fields, we develop a data-driven, one-dimensional, time-dependent model. For model inputs, we use ...


Generation Of Unusually Low Frequency Plasmaspheric Hiss, Lunjin Chen, R. M. Thorne, J. Bortnik, Wen Li, Richard B. Horne, Geoffrey Reeves, C A. Kletzing, W. S. Kurth, G. B. Hospodarsky, Harlan E. Spence, J. B. Blake, Joseph F. Fennell Aug 2014

Generation Of Unusually Low Frequency Plasmaspheric Hiss, Lunjin Chen, R. M. Thorne, J. Bortnik, Wen Li, Richard B. Horne, Geoffrey Reeves, C A. Kletzing, W. S. Kurth, G. B. Hospodarsky, Harlan E. Spence, J. B. Blake, Joseph F. Fennell

Physics Scholarship

Abstract

It has been reported from Van Allen Probe observations that plasmaspheric hiss intensification in the outer plasmasphere, associated with a substorm injection on 30 September 2012, occurred with a peak frequency near 100 Hz, well below the typical plasmaspheric hiss frequency range, extending down to ∼20 Hz. We examine this event of unusually low frequency plasmaspheric hiss to understand its generation mechanism. Quantitative analysis is performed by simulating wave raypaths via the HOTRAY ray tracing code with measured plasma density and calculating raypath-integrated wave gain evaluated using the measured energetic electron distribution. We demonstrate that the growth rate due ...


Nitrate Deposition To Surface Snow At Summit, Greenland, Following The 9 November 2000 Solar Proton Event, Katherine A. Duderstadt, Jack E. Dibb, Charles H. Jackman, Cora E. Randall, Stanley C. Solomon, Michael J. Mills, Nathan A. Schwadron, Harlan E. Spence Jun 2014

Nitrate Deposition To Surface Snow At Summit, Greenland, Following The 9 November 2000 Solar Proton Event, Katherine A. Duderstadt, Jack E. Dibb, Charles H. Jackman, Cora E. Randall, Stanley C. Solomon, Michael J. Mills, Nathan A. Schwadron, Harlan E. Spence

Earth Sciences Scholarship

Abstract

This study considers whether spikes in nitrate in snow sampled at Summit, Greenland, from August 2000 to August 2002 are related to solar proton events. After identifying tropospheric sources of nitrate on the basis of correlations with sulfate, ammonium, sodium, and calcium, we use the three-dimensional global Whole Atmosphere Community Climate Model (WACCM) to examine unaccounted for nitrate spikes. Model calculations confirm that solar proton events significantly impact HOx, NOx, and O3 levels in the mesosphere and stratosphere during the weeks and months following the major 9 November 2000 solar proton event. However, solar proton event ...


Synthesis Of 3-D Coronal-Solar Wind Energetic Particle Acceleration Modules, Nathan A. Schwadron, Matthew J. Gorby, Tibor Torak, Cooper Downs, J. A. Linker, Roberto Lionello, Z. Mikic, P. Riley, Joe Giacalone, Benjamin D.G. Chandran, Kai K. Germaschewski, Philip A. Isenberg, Martin A. Lee, Noe E. Lugaz, Sonya S. Smith, Harlan E. Spence, M. Desai, J. C. Kasper, K. Kozarev, K. E. Korreck, M. L. Stevens, J. F. Cooper, Peter Macneice Jun 2014

Synthesis Of 3-D Coronal-Solar Wind Energetic Particle Acceleration Modules, Nathan A. Schwadron, Matthew J. Gorby, Tibor Torak, Cooper Downs, J. A. Linker, Roberto Lionello, Z. Mikic, P. Riley, Joe Giacalone, Benjamin D.G. Chandran, Kai K. Germaschewski, Philip A. Isenberg, Martin A. Lee, Noe E. Lugaz, Sonya S. Smith, Harlan E. Spence, M. Desai, J. C. Kasper, K. Kozarev, K. E. Korreck, M. L. Stevens, J. F. Cooper, Peter Macneice

Physics Scholarship

1. Introduction Acute space radiation hazards pose one of the most serious risks to future human and robotic exploration. Large solar energetic particle (SEP) events are dangerous to astronauts and equipment. The ability to predict when and where large SEPs will occur is necessary in order to mitigate their hazards. The Coronal-Solar Wind Energetic Particle Acceleration (C-SWEPA) modeling effort in the NASA/NSF Space Weather Modeling Collaborative [Schunk, 2014] combines two successful Living With a Star (LWS) (http://lws. gsfc.nasa.gov/) strategic capabilities: the Earth-Moon-Mars Radiation Environment Modules (EMMREM) [Schwadron et al., 2010] that describe energetic particles and their ...


Radiation Environment At The Moon: Comparisons Of Transport Code Modeling And Measurements From The Crater Instrument, Jamie A. Porter, Lawrence W. Townsend, Harlan E. Spence, Michael J. Golightly, Nathan A. Schwadron, Justin Kasper, Anthony Case, J. B. Blake, Cary Zeitlin Jun 2014

Radiation Environment At The Moon: Comparisons Of Transport Code Modeling And Measurements From The Crater Instrument, Jamie A. Porter, Lawrence W. Townsend, Harlan E. Spence, Michael J. Golightly, Nathan A. Schwadron, Justin Kasper, Anthony Case, J. B. Blake, Cary Zeitlin

Physics Scholarship

Abstract

The Cosmic Ray Telescope for the Effects of Radiation (CRaTER), an instrument carried on the Lunar Reconnaissance Orbiter spacecraft, directly measures the energy depositions by solar and galactic cosmic radiations in its silicon wafer detectors. These energy depositions are converted to linear energy transfer (LET) spectra. High LET particles, which are mainly high-energy heavy ions found in the incident cosmic ray spectrum, or target fragments and recoils produced by protons and heavier ions, are of particular importance because of their potential to cause significant damage to human tissue and electronic components. Aside from providing LET data useful for space ...


Radiation Belt Electron Acceleration By Chorus Waves During The 17 March 2013 Storm, W. Li, R. M. Thorne, Q. Ma, B. Ni, J. Bortnik, D. N. Baker, Harlan E. Spence, Geoffrey Reeves, S. G. Kanekal, J. C. Green, C A. Kletzing, W. S. Kurth, G. B. Hospodarsky, J. B. Blake, Joseph F. Fennell, S. Claudepierre Jun 2014

Radiation Belt Electron Acceleration By Chorus Waves During The 17 March 2013 Storm, W. Li, R. M. Thorne, Q. Ma, B. Ni, J. Bortnik, D. N. Baker, Harlan E. Spence, Geoffrey Reeves, S. G. Kanekal, J. C. Green, C A. Kletzing, W. S. Kurth, G. B. Hospodarsky, J. B. Blake, Joseph F. Fennell, S. Claudepierre

Physics Scholarship

Abstract

Local acceleration driven by whistler-mode chorus waves is fundamentally important for accelerating seed electron populations to highly relativistic energies in the outer radiation belt. In this study, we quantitatively evaluate chorus-driven electron acceleration during the 17 March 2013 storm, when the Van Allen Probes observed very rapid electron acceleration up to several MeV within ~12 hours. A clear radial peak in electron phase space density (PSD) observed near L* ~4 indicates that an internal local acceleration process was operating. We construct the global distribution of chorus wave intensity from the low-altitude electron measurements made by multiple Polar Orbiting Environmental ...


Intense Duskside Lower Band Chorus Waves Observed By Van Allen Probes: Generation And Potential Acceleration Effect On Radiation Belt Electrons, Zhenpeng Su, Hui Zhu, Fuliang Xiao, Huinan Zheng, Yuming Wang, Zhaoguo He, Chao Shen, Chenglong Shen, C. B. Wang, Rui Liu, Min Zhang, Shui Wang, C A. Kletzing, W. S. Kurth, G. B. Hospodarsky, Harlan E. Spence, Geoffrey Reeves, H. O. Funsten, J. B. Blake, D. N. Baker, J. R. Wygant Jun 2014

Intense Duskside Lower Band Chorus Waves Observed By Van Allen Probes: Generation And Potential Acceleration Effect On Radiation Belt Electrons, Zhenpeng Su, Hui Zhu, Fuliang Xiao, Huinan Zheng, Yuming Wang, Zhaoguo He, Chao Shen, Chenglong Shen, C. B. Wang, Rui Liu, Min Zhang, Shui Wang, C A. Kletzing, W. S. Kurth, G. B. Hospodarsky, Harlan E. Spence, Geoffrey Reeves, H. O. Funsten, J. B. Blake, D. N. Baker, J. R. Wygant

Physics Scholarship

Abstract

Local acceleration driven by whistler mode chorus waves largely accounts for the enhancement of radiation belt relativistic electron fluxes, whose favored region is usually considered to be the plasmatrough with magnetic local time approximately from midnight through dawn to noon. On 2 October 2013, the Van Allen Probes recorded a rarely reported event of intense duskside lower band chorus waves (with power spectral density up to 10-3nT 2/Hz) in the low-latitude region outside of L=5. Such chorus waves are found to be generated by the substorm-injected anisotropic suprathermal electrons and have a potentially strong acceleration ...


Chorus Acceleration Of Radiation Belt Relativistic Electrons During March 2013 Geomagnetic Storm, Fuliang Xiao, Chang Yang, Zhaoguo He, Zhenpeng Su, Qinghua Zhou, Yihua He, C A. Kletzing, W. S. Kurth, G. B. Hospodarsky, Harlan E. Spence, Geoffrey Reeves, H. O. Funsten, J. B. Blake, D. N. Baker, J. R. Wygant May 2014

Chorus Acceleration Of Radiation Belt Relativistic Electrons During March 2013 Geomagnetic Storm, Fuliang Xiao, Chang Yang, Zhaoguo He, Zhenpeng Su, Qinghua Zhou, Yihua He, C A. Kletzing, W. S. Kurth, G. B. Hospodarsky, Harlan E. Spence, Geoffrey Reeves, H. O. Funsten, J. B. Blake, D. N. Baker, J. R. Wygant

Physics Scholarship

Abstract

The recent launching of Van Allen probes provides an unprecedent opportunity to investigate variations of the radiation belt relativistic electrons. During the 17-19 March 2013 storm, the Van Allen probes simultaneously detected strong chorus waves and substantial increases in fluxes of relativistic (2 - 4.5 MeV) electrons around L = 4.5. Chorus waves occurred within the lower band 0.1-0.5fce (theelectron equatorial gyrofrequency), with a peak spectral density ∼10-4 nT 2/Hz. Correspondingly, relativistic electron fluxes increased by a factor of 102-103 during the recovery phase compared to the main phase levels. By ...


The Quest For High Power Lasers: Forcing Mutual Coherence In Broad Area Diode Lasers, Jonathan R. Wurtz Apr 2014

The Quest For High Power Lasers: Forcing Mutual Coherence In Broad Area Diode Lasers, Jonathan R. Wurtz

Student Research Projects

This poster explains efforts to improve spatial beam quality of diode array stacks using an external optical feedback system to force coherence of individual diodes.


Understanding Thermometry At Low Temperature, Zain Abbas Apr 2014

Understanding Thermometry At Low Temperature, Zain Abbas

Student Research Projects

Cryogenics play a vital role in building a Dynamic Nuclear Polarization (DNP) target for electron scattering experiments. The target material temperature was monitored using thermometry in order to evaluate their stability for use in the low temperature cryogenic bath of a DNP target. In this project, I investigated there solutions and accuracies of carbon ceramic, Cernox, Allen-Bradley, and thermocouple sensors at five known temperatures.


Analyzing Heavy Photon Search Simulations To Determine The Potential For True Muonium Discovery, Chad N. Civello Apr 2014

Analyzing Heavy Photon Search Simulations To Determine The Potential For True Muonium Discovery, Chad N. Civello

Student Research Projects

The Heavy Photon Search (HPS) is a new experiment at Jefferson Laboratory to search for heavy photons, a particle predicted by dark matter and dark energy extensions to the Standard Model of particle physics, in the mass range of 20 MeV/c2 to 1000 MeV/c2 . The experiment also has the potential to discover true muonium, a bound state of a muon and an antimuon that is predicted to exist, but has never been observed. The true muonium atom should be produced by an electron beam incident on a target, such as the tungsten target used in the ...


Quantifying The Radiation Belt Seed Population In The 17 March 2013 Electron Acceleration Event, A. J. Boyd, Harlan E. Spence, S. Claudepierre, Joseph F. Fennell, J. B. Blake, D. N. Baker, Geoffrey Reeves, D. L. Turner Apr 2014

Quantifying The Radiation Belt Seed Population In The 17 March 2013 Electron Acceleration Event, A. J. Boyd, Harlan E. Spence, S. Claudepierre, Joseph F. Fennell, J. B. Blake, D. N. Baker, Geoffrey Reeves, D. L. Turner

Physics Scholarship

Abstract

We present phase space density (PSD) observations using data from the Magnetic Electron Ion Spectrometer instrument on the Van Allen Probes for the 17 March 2013 electron acceleration event. We confirm previous results and quantify how PSD gradients depend on the first adiabatic invariant. We find a systematic difference between the lower-energy electrons (1-MeV with a source region within the radiation belts. Our observations show that the source process begins with enhancements to the 10s-100s-keV energy seed population, followed by enhancements to the >1-MeV population and eventually leading to enhancements in the multi-MeV electron population these observations provide the ...


Simulations Of Inner Magnetosphere Dynamics With An Expanded Ram-Scb Model And Comparisons With Van Allen Probes Observations, Vania K. Jordanova, Y. Yu, J. T. Niehof, R. M. Skoug, Geoffrey Reeves, C A. Kletzing, Joseph F. Fennell, Harlan E. Spence Apr 2014

Simulations Of Inner Magnetosphere Dynamics With An Expanded Ram-Scb Model And Comparisons With Van Allen Probes Observations, Vania K. Jordanova, Y. Yu, J. T. Niehof, R. M. Skoug, Geoffrey Reeves, C A. Kletzing, Joseph F. Fennell, Harlan E. Spence

Physics Scholarship

Abstract

Simulations from our newly expanded ring current-atmosphere interactions model with self-consistent magnetic field (RAM-SCB), now valid out to 9 R E, are compared for the first time with Van Allen Probes observations. The expanded model reproduces the storm time ring current buildup due to the increased convection and inflow of plasma from the magnetotail. It matches Magnetic Electron Ion Spectrometer (MagEIS) observations of the trapped high-energy (>50 keV) ion flux; however, it underestimates the low-energy (<10 keV) Helium, Oxygen, Proton, and Electron (HOPE) observations. The dispersed injections of ring current ions observed with the Energetic particle, Composition, and Thermal plasma (ECT) suite at high (>20 keV) energy are better reproduced using a high-resolution convection model. In agreement with Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS ...


Competing Source And Loss Mechanisms Due To Wave-Particle Interactions In Earth’S Outer Radiation Belt During The 30 September To 3 October 2012 Geomagnetic Storm, D. L. Turner, V. Angelopoulos, W. Li, J. Bortnik, B. Ni, Q. Ma, R. M. Thorne, S. K. Morley, M. G. Henderson, Geoffrey Reeves, M. Usanova, I. R. Mann, S. Claudepierre, J. B. Blake, D. N. Baker, Chia-Lin L. Huang, Harlan E. Spence, W. S. Kurth, C A. Kletzing, J. V. Rodriguez Mar 2014

Competing Source And Loss Mechanisms Due To Wave-Particle Interactions In Earth’S Outer Radiation Belt During The 30 September To 3 October 2012 Geomagnetic Storm, D. L. Turner, V. Angelopoulos, W. Li, J. Bortnik, B. Ni, Q. Ma, R. M. Thorne, S. K. Morley, M. G. Henderson, Geoffrey Reeves, M. Usanova, I. R. Mann, S. Claudepierre, J. B. Blake, D. N. Baker, Chia-Lin L. Huang, Harlan E. Spence, W. S. Kurth, C A. Kletzing, J. V. Rodriguez

Physics Scholarship

Abstract Drastic variations of Earth’s outer radiation belt electrons ultimately result from various competing source, loss, and transport processes, to which wave-particle interactions are critically important. Using 15 spacecraft including NASA’s Van Allen Probes, THEMIS, and SAMPEX missions and NOAA’s GOES and POES constellations, we investigated the evolution of the outer belt during the strong geomagnetic storm of 30 September to 3 October 2012. This storm’s main phase dropout exhibited enhanced losses to the atmosphere at L*< 4, where the phase space density (PSD) of multi-MeV electrons dropped by over an order of magnitude in1 MeV electrons and energetic protons, SAMPEX >1 MeV electrons, and ground observations of band-limited Pc1-2 wave activity, we show that this sudden loss was consistent ...


Application And Testing Of The L Neural Network With The Self-Consistent Magnetic Field Model Of Ram-Scb, Yiqun Yu, Josef Koller, Vania K. Jordanova, Sorin G. Zaharia, R. Friedel, S. K. Morley, Yue Chen, D. N. Baker, Geoffrey Reeves, Harlan E. Spence Mar 2014

Application And Testing Of The L Neural Network With The Self-Consistent Magnetic Field Model Of Ram-Scb, Yiqun Yu, Josef Koller, Vania K. Jordanova, Sorin G. Zaharia, R. Friedel, S. K. Morley, Yue Chen, D. N. Baker, Geoffrey Reeves, Harlan E. Spence

Physics Scholarship

Abstract

We expanded our previous work on L neural networks that used empirical magnetic field models as the underlying models by applying and extending our technique to drift shells calculated from a physics-based magnetic field model. While empirical magnetic field models represent an average, statistical magnetospheric state, the RAM-SCB model, a first-principles magnetically self-consistent code, computes magnetic fields based on fundamental equations of plasma physics. Unlike the previous L neural networks that include McIlwain L and mirror point magnetic field as part of the inputs, the new L neural network only requires solar wind conditions and the Dst index, allowing ...


On The Cause And Extent Of Outer Radiation Belt Losses During The 30 September 2012 Dropout Event, D. L. Turner, V. Angelopoulos, S. K. Morley, M. G. Henderson, Geoffrey Reeves, W. Li, D. N. Baker, Chia-Lin L. Huang, A. J. Boyd, Harlan E. Spence, S. Claudepierre, J. B. Blake, J. V. Rodriguez Mar 2014

On The Cause And Extent Of Outer Radiation Belt Losses During The 30 September 2012 Dropout Event, D. L. Turner, V. Angelopoulos, S. K. Morley, M. G. Henderson, Geoffrey Reeves, W. Li, D. N. Baker, Chia-Lin L. Huang, A. J. Boyd, Harlan E. Spence, S. Claudepierre, J. B. Blake, J. V. Rodriguez

Physics Scholarship

Abstract

On 30 September 2012, a flux "dropout" occurred throughout Earth's outer electron radiation belt during the main phase of a strong geomagnetic storm. Using eight spacecraft from NASA's Time History of Events and Macroscale Interactions during Substorms (THEMIS) and Van Allen Probes missions and NOAA's Geostationary Operational Environmental Satellites constellation, we examined the full extent and timescales of the dropout based on particle energy, equatorial pitch angle, radial distance, and species. We calculated phase space densities of relativistic electrons, in adiabatic invariant coordinates, which revealed that loss processes during the dropout were > 90% effective throughout the ...


Repad: An Empirical Model Of Pitch Angle Distributions For Energetic Electrons In The Earth's Outer Radiation Belt, Yue Chen, R. Friedel, M. G. Henderson, S. Claudepierre, S. K. Morley, Harlan E. Spence Mar 2014

Repad: An Empirical Model Of Pitch Angle Distributions For Energetic Electrons In The Earth's Outer Radiation Belt, Yue Chen, R. Friedel, M. G. Henderson, S. Claudepierre, S. K. Morley, Harlan E. Spence

Physics Scholarship

Abstract

We have recently conducted a statistical survey on pitch angle distributions of energetic electrons trapped in the Earth's outer radiation belt, and a new empirical model was developed based upon survey results. This model - relativistic electron pitch angle distribution (REPAD) - aims to present statistical pictures of electron equatorial pitch angle distributions, instead of the absolute flux levels, as a function of energy, L shell, magnetic local time, and magnetic activity. To quantify and facilitate this statistical survey, we use Legendre polynomials to fit long-term in situ directional fluxes observed near the magnetic equator from three missions: CRRES, Polar ...