Physics Commons^™

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 & Astronomy

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 with pitch angle scattering …

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 & Astronomy

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, …

Event-Specific Chorus Wave And Electron Seed Population Models In Dream3d Using The Van Allen Probes, Weichao Tu, G. S. Cunningham, Y. Chen, S. K. Morley, Geoffrey Reeves, J. B. Blake, D. N. Baker, Harlan E. Spence

Physics & Astronomy

Abstract

The DREAM3D diffusion model is applied to Van Allen Probes observations of the fast dropout and strong enhancement of MeV electrons during the October 2012 "double-dip" storm. We show that in order to explain the very different behavior in the two "dips," diffusion in all three dimensions (energy, pitch angle, and L^o) coupled with data-driven, event-specific inputs, and boundary conditions is required. Specifically, we find that outward radial diffusion to the solar wind-driven magnetopause, an event-specific chorus wave model, and a dynamic lower-energy seed population are critical for modeling the dynamics. In contrast, models that include only …

Gradual Diffusion And Punctuated Phase Space Density Enhancements Of Highly Relativistic Electrons: Van Allen Probes Observations, D. N. Baker, A. Jaynes, X. Li, M. G. Henderson, S. G. Kanekal, Geoffrey Reeves, Harlan E. Spence, S. Claudepierre, Joseph F. Fennell, M. K. Hudson, R. M. Thorne, J. C. Foster, P. J. Erickson, D. M. Malaspina, J. R. Wygant, A. J. Boyd, C A. Kletzing, A. Drozdov, Y. Y. Shprits

Physics & Astronomy

Abstract

The dual-spacecraft Van Allen Probes mission has provided a new window into mega electron volt (MeV) particle dynamics in the Earth's radiation belts. Observations (up to E ~10 MeV) show clearly the behavior of the outer electron radiation belt at different timescales: months-long periods of gradual inward radial diffusive transport and weak loss being punctuated by dramatic flux changes driven by strong solar wind transient events. We present analysis of multi-MeV electron flux and phase space density (PSD) changes during March 2013 in the context of the first year of Van Allen Probes operation. This March period demonstrates the …

Evolution Of The Cooper Pair Insulator Phase In A-Bi Films Grown On Nanohoneycomb Substrates With Varying Surface Topography, J C. Joy, X Zhang, C Zhao, Shawna M. Hollen, J M. Valles Jr., G. E. Fernandes, J M. Xu

Physics & Astronomy

No abstract provided.

Van Allen Probes Observations Of Direct Wave-Particle Interactions, Joseph F. Fennell, J. Roeder, W. S. Kurth, M. G. Henderson, B. A. Larsen, G. B. Hospodarsky, J. R. Wygant, S. Claudepierre, J. B. Blake, Harlan E. Spence, J. H. Clemmons, H. O. Funsten, C A. Kletzing, Geoffrey Reeves

Physics & Astronomy

Abstract

Quasiperiodic increases, or "bursts," of 17-26 keV electron fluxes in conjunction with chorus wave bursts were observed following a plasma injection on 13 January 2013. The pitch angle distributions changed during the burst events, evolving from sin^N(α) to distributions that formed maxima at α = 75-80°, while fluxes at 90° and <60° remained nearly unchanged. The observations occurred outside of the plasmasphere in the postmidnight region and were observed by both Van Allen Probes. Density, cyclotron frequency, and pitch angle of the peak flux were used to estimate resonant electron energy. The result of ∼15-35 keV is consistent with the energies of the electrons showing the flux enhancements and corresponds to electrons in and above the steep flux gradient that signals the presence of an Alfvén boundary in the plasma. The cause of the quasiperiodic nature (on the order of a few minutes) of the bursts is not understood at this time.

Effect Of Emic Waves On Relativistic And Ultrarelativistic Electron Populations: Ground-Based And Van Allen Probes Observations, M. Usanova, A. Drozdov, K. Orlova, I. R. Mann, Y. Y. Shprits, M. T. Robertson, D. L. Turner, D. K. Milling, A. Kale, D. N. Baker, S. A. Thaller, Geoffrey Reeves, Harlan E. Spence, C A. Kletzing, J. R. Wygant

Physics & Astronomy

Abstract

We study the effect of electromagnetic ion cyclotron (EMIC) waves on the loss and pitch angle scattering of relativistic and ultrarelativistic electrons during the recovery phase of a moderate geomagnetic storm on 11 October 2012. The EMIC wave activity was observed in situ on the Van Allen Probes and conjugately on the ground across the Canadian Array for Real-time Investigations of Magnetic Activity throughout an extended 18 h interval. However, neither enhanced precipitation of >0.7 MeV electrons nor reductions in Van Allen Probe 90° pitch angle ultrarelativistic electron flux were observed. Computed radiation belt electron pitch angle diffusion rates …

Radiation Modeling In The Earth And Mars Atmospheres Using Lro/Crater With The Emmrem Module, Colin J. Joyce, Nathan A. Schwadron, Jody K. Wilson, Harlan E. Spence, Justin Kasper, Michael J. Golightly, J. B. Blake, Lawrence W. Townsend, Anthony Case, E. Semones, Sonya S. Smith, Cary Zeitlin

Physics & Astronomy

Abstract

We expand upon the efforts of Joyce et al. (2013), who computed the modulation potential at the Moon using measurements from the Cosmic Ray Telescope for the Effects of Radiation (CRaTER) instrument on the Lunar Reconnaissance Orbiter (LRO) spacecraft along with data products from the Earth-Moon-Mars Radiation Environment Module (EMMREM). Using the computed modulation potential, we calculate galactic cosmic ray (GCR) dose and dose equivalent rates in the Earth and Mars atmospheres for various altitudes over the course of the LRO mission. While we cannot validate these predictions by directly comparable measurement, we find that our results conform to …

Quantifying Hiss-Driven Energetic Electron Precipitation: A Detailed Conjunction Event Analysis, W. Li, B. Ni, R. M. Thorne, J. Bortnik, Y. Nishimura, J. C. Green, C A. Kletzing, W. S. Kurth, G. B. Hospodarsky, Harlan E. Spence, Geoffrey Reeves, J. B. Blake, Joseph F. Fennell, S. Claudepierre, X. Gu

Physics & Astronomy

Abstract

We analyze a conjunction event between the Van Allen Probes and the low-altitude Polar Orbiting Environmental Satellite (POES) to quantify hiss-driven energetic electron precipitation. A physics-based technique based on quasi-linear diffusion theory is used to estimate the ratio of precipitated and trapped electron fluxes (R), which could be measured by the two-directional POES particle detectors, using wave and plasma parameters observed by the Van Allen Probes. The remarkable agreement between modeling and observations suggests that this technique is applicable for quantifying hiss-driven electron scattering near the bounce loss cone. More importantly, R in the 100-300 keV energy channel measured …

An Empirically Observed Pitch-Angle Diffusion Eigenmode In The Earth's Electron Belt Near L* = 5.0, T. P. O'Brien, S. Claudepierre, J. B. Blake, Joseph F. Fennell, J. H. Clemmons, J. Roeder, Harlan E. Spence, Geoffrey Reeves, D. N. Baker

Physics & Astronomy

Abstract

Using data from NASA's Van Allen Probes, we have identified a synchronized exponential decay of electron flux in the outer zone, near L^* = 5.0. Exponential decays strongly indicate the presence of a pure eigenmode of a diffusion operator acting in the synchronized dimension(s). The decay has a time scale of about 4 days with no dependence on pitch angle. While flux at nearby energies and L^* is also decaying exponentially, the decay time varies in those dimensions. This suggests the primary decay mechanism is elastic pitch angle scattering, which itself depends on energy and L ^{* …}

Assessing The Flexibility Of Research-Based Instructional Strategies: Implementing Tutorials In Introductory Physics In The Lecture Environment, Mila Kryjevskaia, Andrew Boudreaux, Dustin Heins

Physics & Astronomy

Materials from Tutorials in Introductory Physics, originally designed and implemented by the Physics Education Group at the University of Washington, were used in modified form as interactive lectures under conditions significantly different from those suggested by the curriculum developers. Student learning was assessed using tasks drawn from the physics education research literature. Use of tutorials in the interactive lecture format yielded gains in student understanding comparable to those obtained through the canonical tutorial implementation at the University of Washington, suggesting that student engagement with the intellectual steps laid out in the tutorials, rather than the specific strategies used in …

Promoting And Assessing Student Metacognition In Physics, Alistair Mcinerny, Andrew Boudreaux, Mila Kryjevskaia, Sara Julin

Physics & Astronomy

A scaffolded metacognition activity was incorporated into the laboratory component of the introductory physics course at Western Washington University (WWU) and Whatcom Community College (WCC). Each week, students wrote reflectively to contrast their initial and current understanding of a specific physics topic, and described the "trigger" events that led them to change their thinking. Goals were to enhance conceptual understanding as well as the depth and quality of student reflection. A coding scheme was developed to evaluate student reflections. We present the scaffolded activity and coding scheme, as well as preliminary findings about changes in student reflection over time and …

Excitation Of Emic Waves Detected By The Van Allen Probes On 28 April 2013, J. C. Zhang, A A. Saiken, Lynn M. Kistler, Charles W. Smith, Harlan E. Spence, Christoforos Mouikis, Roy B. Torbert, Bradford Larsen, Geoffrey Reeves, R. M. Skoug, H. O. Funsten, W. S. Kurth, C A. Kletzing, R. C. Allen, V K. Jordanova

Physics & Astronomy

Abstract

We report the wave observations, associated plasma measurements, and linear theory testing of electromagnetic ion cyclotron (EMIC) wave events observed by the Van Allen Probes on 28 April 2013. The wave events are detected in their generation regions as three individual events in two consecutive orbits of Van Allen Probe-A, while the other spacecraft, B, does not detect any significant EMIC wave activity during this period. Three overlapping H⁺ populations are observed around the plasmapause when the waves are excited. The difference between the observational EMIC wave growth parameter (E_h) and the theoretical EMIC instability parameter …

Prompt Energization Of Relativistic And Highly Relativistic Electrons During A Substorm Interval: Van Allen Probes Observations, J. C. Foster, P. J. Erickson, D. N. Baker, S. Claudepierre, C A. Kletzing, W. S. Kurth, Geoffrey Reeves, S. A. Thaller, Harlan E. Spence, Y. Y. Shprits, J. R. Wygant

Physics & Astronomy

Abstract

On 17 March 2013, a large magnetic storm significantly depleted the multi-MeV radiation belt. We present multi-instrument observations from the Van Allen Probes spacecraft Radiation Belt Storm Probe A and Radiation Belt Storm Probe B at ~6 Re in the midnight sector magnetosphere and from ground-based ionospheric sensors during a substorm dipolarization followed by rapid reenergization of multi-MeV electrons. A 50% increase in magnetic field magnitude occurred simultaneously with dramatic increases in 100 keV electron fluxes and a 100 times increase in VLF wave intensity. The 100 keV electrons and intense VLF waves provide a seed population and energy …

Nonstorm Time Dynamics Of Electron Radiation Belts Observed By The Van Allen Probes, Zhenpeng Su, Fuliang Xiao, Huinan Zheng, Zhaoguo He, Hui Zhu, Min Zhang, Chao Shen, Yuming Wang, 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

Physics & Astronomy

Abstract

Storm time electron radiation belt dynamics have been widely investigated for many years. Here we present a rarely reported nonstorm time event of electron radiation belt evolution observed by the Van Allen Probes during 21-24 February 2013. Within 2 days, a new belt centering around L=5.8 formed and gradually merged with the original outer belt, with the enhancement of relativistic electron fluxes by a factor of up to 50. Strong chorus waves (with power spectral density up to 10^-4nT²/Hz) occurred in the region L>5. Taking into account the local acceleration driven by these chorus …

James Van Allen And His Namesake Nasa Mission, D. N. Baker, V. C. Hoxie, A. Jaynes, A. Kale, S. G. Kanekal, X. Li, Geoffrey Reeves, Harlan E. Spence

Physics & Astronomy

Abstract

In many ways, James A. Van Allen defined and “invented” modern space research. His example showed the way for government-university partners to pursue basic research that also served important national and international goals. He was a tireless advocate for space exploration and for the role of space science in the spectrum of national priorities.

Science Goals And Overview Of The Radiation Belt Storm Probes (Rbsp) Energetic Particle, Composition, And Thermal Plasma (Ect) Suite On Nasa’S Van Allen Probes Mission, Harlan E. Spence, G. D. Reeves, D. N. Baker, J. B. Blake, M. Bolton, S. Bourdarie, A. A. Chan, S. G. Claudepierre, J. H. Clemmons, J. P. Cravens, S. R. Elkington, J. F. Fennell

Physics & Astronomy

The Radiation Belt Storm Probes (RBSP)-Energetic Particle, Composition, and Thermal Plasma (ECT) suite contains an innovative complement of particle instruments to ensure the highest quality measurements ever made in the inner magnetosphere and radiation belts. The coordinated RBSP-ECT particle measurements, analyzed in combination with fields and waves observations and state-of-the-art theory and modeling, are necessary for understanding the acceleration, global distribution, and variability of radiation belt electrons and ions, key science objectives of NASA’s Living With a Star program and the Van Allen Probes mission. The RBSP-ECT suite consists of three highly-coordinated instruments: the Magnetic Electron Ion Spectrometer (MagEIS), the …

The Magnetic Electron Ion Spectrometer (Mageis) Instruments Aboard The Radiation Belt Storm Probes (Rbsp) Spacecraft, J. B. Blake, P. A. Carranza, S. G. Claudepierre, J. H. Clemmons, W. R. Crain, Y. Dotan, J. F. Fennell, F. H. Fuentes, R. M. Galvan, J. S. George, M. G. Henderson, M. Lalic

Physics & Astronomy

This paper describes the Magnetic Electron Ion Spectrometer (MagEIS) instruments aboard the RBSP spacecraft from an instrumentation and engineering point of view. There are four magnetic spectrometers aboard each of the two spacecraft, one low-energy unit (20–240 keV), two medium-energy units (80–1200 keV), and a high-energy unit (800–4800 keV). The high unit also contains a proton telescope (55 keV–20 MeV). The magnetic spectrometers focus electrons within a selected energy pass band upon a focal plane of several silicon detectors where pulse-height analysis is used to determine if the energy of the incident electron is appropriate for the electron momentum selected …

Helium, Oxygen, Proton, And Electron (Hope) Mass Spectrometer For The Radiation Belt Storm Probes Mission, H. O. Funsten, R. M. Skoug, A. A. Guthrie, E. A. Macdonald, J. R. Baldonado, R. W. Harper, K. C. Henderson, K. H. Kihara, J. E. Lake, B. A. Larsen, A. D. Puckett, V. J. Vigil, Harlan E. Spence

Physics & Astronomy

The HOPE mass spectrometer of the Radiation Belt Storm Probes (RBSP) mission (renamed the Van Allen Probes) is designed to measure the in situ plasma ion and electron fluxes over 4π sr at each RBSP spacecraft within the terrestrial radiation belts. The scientific goal is to understand the underlying physical processes that govern the radiation belt structure and dynamics. Spectral measurements for both ions and electrons are acquired over 1 eV to 50 keV in 36 log-spaced steps at an energy resolution ΔE FWHM/E≈15 %. The dominant ion species (H+, He+, and O+) of the magnetosphere are identified using foil-based …

Measurements Of Galactic Cosmic Ray Shielding With The Crater Instrument, C. Zeitlin, A. W. Case, Harlan E. Spence, Nathan A. Schwadron, M. Golightly, Jody K. Wilson, J. C. Kasper, J. B. Blake, M. D. Looper, J. E. Mazur, L. W. Townsend, Y. Iwata

Physics & Astronomy

[1] The Cosmic Ray Telescope for the Effects of Radiation (CRaTER) instrument aboard the Lunar Reconnaissance Orbiter has been measuring energetic charged particles from the galactic cosmic rays (GCRs) and solar particle events in lunar orbit since 2009. CRaTER includes three pairs of silicon detectors, separated by pieces of tissue-equivalent plastic that shield two of the three pairs from particles incident at the zenith-facing end of the telescope. Heavy-ion beams studied in previous ground-based work have been shown to be reasonable proxies for the GCRs when their energies are sufficiently high. That work, which included GCR simulations, led to predictions …

Early Science Results From The Nasa Van Allen Probes Mission Rbsp-Ect Instrument Suite, Harlan E. Spence, Geoff Reeves, Rbspect Team

Physics & Astronomy

No abstract provided.

The Radiation Environment Near The Lunar Surface: Crater Observations And Geant4 Simulations, M. D. Looper, J. E. Mazur, J. B. Blake, Harlan E. Spence, Nathan A. Schwadron, M. J. Golightly, A. W. Case, J. C. Kasper, L. W. Townsend

Physics & Astronomy

[1] At the start of the Lunar Reconnaissance Orbiter mission in 2009, its Cosmic Ray Telescope for the Effects of Radiation instrument measured the radiation environment near the Moon during the recent deep solar minimum, when galactic cosmic rays (GCRs) were at the highest level observed during the space age. We present observations that show the combined effects of GCR primaries, secondary particles (“albedo”) created by the interaction of GCRs with the lunar surface, and the interactions of these particles in the shielding material overlying the silicon solid-state detectors of the Cosmic Ray Telescope for the Effects of Radiation. We …

New Insight Into The Inner Magnetosphere Plasma Regimes With The Van Allen Probes (Rbsp), Joerg-Micha Jahn, Richard E. Denton, Herbert O. Funsten, Geoff Reeves, Harlan E. Spence

Physics & Astronomy

No abstract provided.

Towards In Situ Correlation Of Atomic Structure And Device Functionality In Graphene-Based Devices, Shawna M. Hollen, N M. Santagata, Justin R. Young, Jay A. Gupta, Ezekiel Johnston-Halperin

Physics & Astronomy

No abstract provided.

Transport Behavior Of Ultrathin Films With Nanothickness Undulations In The Strongly Localized Regime, J C. Joy, Shawna M. Hollen, C Zhao, G. E. Fernandes, J M. Xu, J M. Valles Jr.

Physics & Astronomy

No abstract provided.

Observation Of The Collapse Of The Cooper Pair Phase Coherence Length At A Superconductor To Insulator Transition, J M. Valles Jr., Shawna M. Hollen, G. E. Fernandes, Jimmy Xu

Physics & Astronomy

No abstract provided.

Collapse Of The Cooper Pair Phase Coherence Length At A Superconductor-To-Insulator Transition, Shawna M. Hollen, G. E. Fernandes, J. M. Xu, J M. Valles Jr.

Physics & Astronomy

We present investigations of the superconductor-to-insulator transition (SIT) of uniform a-Bi films using a technique sensitive to Cooper pair phase coherence. The films are perforated with a nanohoneycomb array of holes to form a multiply connected geometry and subjected to a perpendicular magnetic field. Film magnetoresistances on the superconducting side of the SIT oscillate with a period dictated by the superconducting flux quantum and the areal hole density. The oscillations disappear close to the SIT critical point to leave a monotonically rising magnetoresistance that persists in the insulating phase. These observations indicate that the Cooper pair phase coherence length, which …

The Crater Special Issue Of Space Weather: Building The Observational Foundation To Deduce Biological Effects Of Space Radiation, Nathan A. Schwadron, Sonya S. Smith, Harlan E. Spence

Physics & Astronomy

[1] The United States is preparing for exploration beyond low-Earth Orbit (LEO). However, the space radiation environment poses significant risks. The radiation hazard is potentially severe but not sufficiently well characterized to determine if long missions outside LEO can be accomplished with acceptable risk [Cucinotta et al., 2001; Schwadron et al., 2010; Cucinotta et al., 2010]. Radiation hazards may be over- or under-stated through incomplete characterization in terms of net quantities such as accumulated dose. Time-dependent characterization often changes acute risk estimates [NCRP, 1989; Cucinotta, 1999; Cucinotta et al., 2000; George et al., 2002]. For example, events with high accumulated …

The First Cosmic Ray Albedo Proton Map Of The Moon, Jody K. Wilson, Harlan E. Spence, Justin Kasper, Michael Golightly, J. B. Blake, J. E. Mazur, L. W. Townsend, A. W. Case, M. D. Looper, C. Zeitlin, Nathan A. Schwadron

Physics & Astronomy

[1] Neutrons emitted from the Moon are produced by the impact of galactic cosmic rays (GCRs) within the regolith. GCRs are high-energy particles capable of smashing atomic nuclei in the lunar regolith and producing a shower of energetic protons, neutrons and other subatomic particles. Secondary particles that are ejected out of the regolith become “albedo” particles. The neutron albedo has been used to study the hydrogen content of the lunar regolith, which motivates our study of albedo protons. In principle, the albedo protons should vary as a function of the input GCR source and possibly as a result of surface …

Lunar Radiation Environment And Space Weathering From The Cosmic Ray Telescope For The Effects Of Radiation (Crater), Nathan A. Schwadron, T. Baker, B. Blake, A. W. Case, J. F. Cooper, M. Golightly, Andrew P. Jordan, Colin J. Joyce, J. Kasper, K. Kozarev, J. Mislinski, J. Mazur, Harlan E. Spence

Physics & Astronomy

[1] The Cosmic Ray Telescope for the Effects of Radiation (CRaTER) measures linear energy transfer by Galactic Cosmic Rays (GCRs) and Solar Energetic Particles (SEPs) on the Lunar Reconnaissance Orbiter (LRO) Mission in a circular, polar lunar orbit. GCR fluxes remain at the highest levels ever observed during the space age. One of the largest SEP events observed by CRaTER during the LRO mission occurred on June 7, 2011. We compare model predictions by the Earth-Moon-Mars Radiation Environment Module (EMMREM) for both dose rates from GCRs and SEPs during this event with results from CRaTER. We find agreement between these …