Physics Commons^™

Cross-Disciplinary Learning Index: A Quantitative Measure Of Cross-Disciplinary Learning About Energy, Todd Haskell, Emily Borda, Andrew Boudreaux

Physics & Astronomy

The structure of many science programs at the college level assumes that students are able to draw on and integrate ideas from multiple disciplinary contexts. However, most assessment tools focus on learning in the context of a single discipline. We describe the development and validation of an instrument to measure how well students are able to combine energy ideas from different disciplines into a coherent understanding of a phenomenon. The final version of the instrument consists of a pair of multiple-choice online assessments, along with a metric calculated from the assessment scores: the cross disciplinary learning index (CDLI). The items …

Physics Inventory Of Quantitative Literacy: A Tool For Assessing Mathematical Reasoning In Introductory Physics, Suzanne W. Brahmia, Alexis Olsho, Trevor I. Smith, Andrew Boudreaux, Philip Eaton, Charlotte Zimmerman

Physics & Astronomy

One desired outcome of introductory physics instruction is that students will develop facility with reasoning quantitatively about physical phenomena. Little research has been done regarding how students develop the algebraic concepts and skills involved in reasoning productively about physics quantities, which is different from either understanding of physics concepts or problem-solving abilities. We introduce the Physics Inventory of Quantitative Literacy (PIQL) as a tool for measuring Quantitative Literacy, a foundation of mathematical reasoning, in the context of introductory physics. We present the development of the PIQL and evidence of its validity for use in calculus-based introductory physics courses. Unlike …

How Curriculum Developers Cognitive Theories Influence Curriculum Development, Andrew Boudreaux, Andy Elby

Physics & Astronomy

[This paper is part of the Focused Collection on Curriculum Development: Theory into Design.] When we examined student responses to questions about the direction of the static friction force in various situations, we both had strong ideas about how to write a tutorial to promote deeper understanding. But our ideas were quite different. In this theoretical paper, we present the two contrasting tutorials and show how their differences can be traced to different theoretical orientations toward cognition and learning. We do not claim that one tutorial—or the theoretical framework loosely associated with it—is superior. Instead, we hope to illustrate two …

Designing Research-Based Instructional Materials That Leverage Dual-Process Theories Of Reasoning: Insights From Testing One Specific, Theory-Driven Intervention, Mila Kryjevskaia, Mackenzie R. Stetzer, Beth A. Lindsey, Alistair Mcinerny, Paula R. L. Heron, Andrew Boudreaux

Physics & Astronomy

[This paper is part of the Focused Collection on Curriculum Development: Theory into Design.] Research in physics education has contributed substantively to improvements in the learning and teaching of university physics by informing the development of research-based instructional materials for physics courses. Reports on the design of these materials have tended to focus on overall improvements in student performance, while the role of theory in informing the development, refinement, and assessment of the materials is often not clearly articulated. In this article, we illustrate how dual-process theories of reasoning and decision making have guided the ongoing development, testing, and analysis …

Toward A Framework For The Natures Of Proportional Reasoning In Introductory Physics, Andrew Boudreaux, Stephen E. Kanim, Alexis Olsho, Suzanne W. Brahmia, Charlotte Zimmerman, Trevor I. Smith

Physics & Astronomy

We present a set of modes of reasoning about ratio and proportion as a means of operationalizing expert practice in physics. These modes, or natures of proportional reasoning, stem from consideration of how physicists reason in context and are informed by prior work in physics and mathematics education. We frame the natures as the core of an emerging framework for proportional reasoning in introductory physics, that will categorize the uses of proportional reasoning in introductory physics contexts, and provide guidance for the development of reliable assessments. We share results from preliminary assessment items indicating that university physics students have difficulty …

Framework For The Natures Of Negativity In Introductory Physics, Suzanne W. Brahmia, Alexis Olsho, Trevor I. Smith, Andrew Boudreaux

Physics & Astronomy

Mathematical reasoning skills are a desired outcome of many introductory physics courses, particularly calculus-based physics courses. Novices can struggle to understand the many roles signed numbers play in physics contexts, and recent evidence shows that unresolved struggle can carry over to subsequent physics courses. Positive and negative quantities are ubiquitous in physics, and the sign carries important and varied meanings. The mathematics education research literature documents the cognitive challenge of conceptualizing negative numbers as mathematical objects—both for experts, historically, and for novices as they learn. We contribute to the small but growing body of research in physics contexts that examines …

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 & Astronomy

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

Physics & Astronomy

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 the occupied Cu(111) …

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 & Astronomy

No abstract provided.

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 & Astronomy

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 developed …

How Accurate Are Physics Students In Evaluating Changes In Their Understanding?, Therese Claire, Tija L. Tippett, Andrew Boudreaux

Physics & Astronomy

An assessment question involving Newton’s 2nd law was administered in a physics course for preservice elementary teachers before and again after instruction. The posttest included a prompt asking students to describe the specific ways their thinking changed. Student reasoning was coded for physics content accuracy; many students exhibited changes from primitive, experientially-based reasoning to more formal reasoning. Students' self-reported reflections were then compared to the differences in the pre- and posttest codes. We find that many students do not identify substantive changes in their reasoning, while other students reflect at only a surface level. We also find that some students …

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 & Astronomy

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

Physics & Astronomy

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 up …

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 & Astronomy

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

Physics & Astronomy

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 results show …

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 & Astronomy

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

Physics & Astronomy

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 poloidal mode …

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 & Astronomy

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 near-perpendicular …

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 & Astronomy

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 GCR …

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 & Astronomy

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 …

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 & Astronomy

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 effects, with the Next …

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 & Astronomy

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

Physics & Astronomy

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

Physics & Astronomy

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 effect …

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 & Astronomy

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 0.1-0.5f_ce (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 means of …

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 & Astronomy

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

Physics & Astronomy

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 …

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 …

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.

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 & Astronomy

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 …