14 results on '"Scott R. Bounds"'
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2. Determining the Wave Vector Direction of Equatorial Fast Magnetosonic Waves
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Kyungguk Min, Craig Kletzing, Robert F. Pfaff, Terrance Averkamp, Scott A. Boardsen, Scott R. Bounds, and George Hospodarsky
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Physics ,Geophysics ,010504 meteorology & atmospheric sciences ,0103 physical sciences ,General Earth and Planetary Sciences ,Direction vector ,010303 astronomy & astrophysics ,01 natural sciences ,0105 earth and related environmental sciences ,Computational physics - Published
- 2018
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3. Phase sorting wave‐particle correlator
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Scott R. Bounds, Craig Kletzing, S. R. Kaeppler, J. S. Dolan, M. P. Dombrowski, and James LaBelle
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Physics ,business.product_category ,010504 meteorology & atmospheric sciences ,business.industry ,Phase (waves) ,Electron ,Plasma oscillation ,01 natural sciences ,Computational physics ,Phase-locked loop ,Geophysics ,Optics ,Wave–particle duality ,Rocket ,Space and Planetary Science ,0103 physical sciences ,Modulation (music) ,Calibration ,business ,010303 astronomy & astrophysics ,0105 earth and related environmental sciences - Abstract
Wave-particle correlations, particularly of Langmuir waves and electrons, have been the subject of significant interest extending back to the 1970's. Often, these correlations have been simply observing modulation of the electrons at the plasma frequency with no phase resolution. The first phase-resolving correlators were developed at UC Berkeley in the late 1980's and reported by Ergun in the early 1990's. A design is presented which further improves on phase resolution in correlations of Langmuir waves and electrons with phase resolution of 22.5 degrees. In this technique, a phase-lock-loop (PLL) is used to lock onto the wave and subdivide the phase. Electrons are sorted on-the-fly as they arrive into the phase bins. Discussed are details of accurate timing, testing, and calibration of this system as well as results from rocket flights in which statistically significant phase correlations have been observed.
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- 2017
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4. Estimates of terms in Ohm's law during an encounter with an electron diffusion region
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Per-Arne Lindqvist, Frederick Wilder, Roy B. Torbert, Thomas E. Moore, Matthew R. Argall, H. A. Faith, K. A. Goodrich, Craig Kletzing, Charlie J. Farrugia, John C. Dorelli, Christopher T. Russell, James L. Burch, T. D. Phan, Werner Magnes, Robert J. Strangeway, William Daughton, Daniel J. Gershman, Göran Marklund, Scott R. Bounds, J. R. Shuster, Robert E. Ergun, Levon A. Avanov, Yu. V. Khotyaintsev, Barbara L. Giles, and Craig J. Pollock
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Physics ,Ohm's law ,010504 meteorology & atmospheric sciences ,Geophysics ,Electron ,Dissipation ,01 natural sciences ,Computational physics ,symbols.namesake ,Physics::Space Physics ,0103 physical sciences ,symbols ,General Earth and Planetary Sciences ,Magnetopause ,Astrophysics::Earth and Planetary Astrophysics ,Diffusion (business) ,010303 astronomy & astrophysics ,Event (particle physics) ,Pressure gradient ,0105 earth and related environmental sciences ,Three dimensional model - Abstract
We present measurements from the Magnetospheric Multiscale (MMS) mission taken during a reconnection event on the dayside magnetopause which includes a passage through an electron diffusion region ...
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- 2016
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5. Using the cold plasma dispersion relation and whistler mode waves to quantify the antenna sheath impedance of the Van Allen Probes EFW instrument
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Scott R. Bounds, David Hartley, John W. Bonnell, Ondrej Santolik, Craig Kletzing, Clare E. J. Watt, William S. Kurth, John R. Wygant, George Hospodarsky, and T. F. Averkamp
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Physics ,Hiss ,010504 meteorology & atmospheric sciences ,Wave propagation ,01 natural sciences ,Computational physics ,Geophysics ,Nuclear magnetic resonance ,Space and Planetary Science ,Surface wave ,Dispersion relation ,Electric field ,Physics::Space Physics ,0103 physical sciences ,Van Allen Probes ,Antenna (radio) ,010303 astronomy & astrophysics ,0105 earth and related environmental sciences ,Wave power - Abstract
Cold plasma theory and parallel wave propagation are often assumed when approximating the whistler mode magnetic field wave power from electric field observations. The current study is the first to include the wave normal angle from the Electric and Magnetic Field Instrument Suite and Integrated Science package on board the Van Allen Probes in the conversion factor, thus allowing for the accuracy of these assumptions to be quantified. Results indicate that removing the assumption of parallel propagation does not significantly affect calculated plasmaspheric hiss wave powers. Hence, the assumption of parallel propagation is valid. For chorus waves, inclusion of the wave normal angle in the conversion factor leads to significant alterations in the distribution of wave power ratios (observed/ calculated); the percentage of overestimates decreases, the percentage of underestimates increases, and the spread of values is significantly reduced. Calculated plasmaspheric hiss wave powers are, on average, a good estimate of those observed, whereas calculated chorus wave powers are persistently and systematically underestimated. Investigation of wave power ratios (observed/calculated), as a function of frequency and plasma density, reveals a structure consistent with signal attenuation via the formation of a plasma sheath around the Electric Field and Waves spherical double probes instrument. A simple, density-dependent model is developed in order to quantify this effect of variable impedance between the electric field antenna and the plasma interface. This sheath impedance model is then demonstrated to be successful in significantly improving agreement between calculated and observed power spectra and wave powers.
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- 2016
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6. Survey of the frequency dependent latitudinal distribution of the fast magnetosonic wave mode from Van Allen Probes Electric and Magnetic Field Instrument and Integrated Science waveform receiver plasma wave analysis
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Mark J. Engebretson, Craig Kletzing, Sebastian de Pascuale, John R. Wygant, Robert F. Pfaff, Scott A. Boardsen, Scott R. Bounds, James L. Green, William S. Kurth, George Hospodarsky, and Terrance Averkamp
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Physics ,010504 meteorology & atmospheric sciences ,Whistler ,Waves in plasmas ,business.industry ,Plane wave ,Plasmasphere ,Magnetosonic wave ,Polarization (waves) ,01 natural sciences ,Computational physics ,symbols.namesake ,Geophysics ,Optics ,Space and Planetary Science ,Van Allen radiation belt ,0103 physical sciences ,symbols ,Van Allen Probes ,business ,010303 astronomy & astrophysics ,0105 earth and related environmental sciences - Abstract
We present a statistical survey of the latitudinal structure of the fast magnetosonic wave mode detected by the Van Allen Probes spanning the time interval of 21 September 2012 to 1 August 2014. We show that statistically, the latitudinal occurrence of the wave frequency (f) normalized by the local proton cyclotron frequency (f(sub cP)) has a distinct funnel-shaped appearance in latitude about the magnetic equator similar to that found in case studies. By comparing the observed E/B ratios with the model E/B ratio, using the observed plasma density and background magnetic field magnitude as input to the model E/B ratio, we show that this mode is consistent with the extra-ordinary (whistler) mode at wave normal angles (theta(sub k)) near 90 deg. Performing polarization analysis on synthetic waveforms composed from a superposition of extra-ordinary mode plane waves with theta(sub k) randomly chosen between 87 and 90 deg, we show that the uncertainty in the derived wave normal is substantially broadened, with a tail extending down to theta(sub k) of 60 deg, suggesting that another approach is necessary to estimate the true distribution of theta(sub k). We find that the histograms of the synthetically derived ellipticities and theta(sub k) are consistent with the observations of ellipticities and theta(sub k) derived using polarization analysis.We make estimates of the median equatorial theta(sub k) by comparing observed and model ray tracing frequency-dependent probability occurrence with latitude and give preliminary frequency dependent estimates of the equatorial theta(sub k) distribution around noon and 4 R(sub E), with the median of approximately 4 to 7 deg from 90 deg at f/f(sub cP) = 2 and dropping to approximately 0.5 deg from 90 deg at f/f(sub cP) = 30. The occurrence of waves in this mode peaks around noon near the equator at all radial distances, and we find that the overall intensity of these waves increases with AE*, similar to findings of other studies.
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- 2016
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7. Van Allen Probes investigation of the large‐scale duskward electric field and its role in ring current formation and plasmasphere erosion in the 1 June 2013 storm
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Cynthia A Cattell, Aaron Breneman, Kris Kersten, Lei Dai, S. De Pascuale, John R. Wygant, Scott R. Bounds, Matina Gkioulidou, George Hospodarsky, Craig Kletzing, John W. Bonnell, Scott Thaller, and J. F. Fennell
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Physics ,Geomagnetic storm ,Plasma sheet ,Plasmasphere ,Geophysics ,Magnetic field ,Computational physics ,Space and Planetary Science ,Electric field ,Physics::Space Physics ,Van Allen Probes ,Pitch angle ,Ring current - Abstract
Using the Van Allen Probes, we investigate the enhancement in the large-scale duskward convection electric field during the geomagnetic storm (Dst similar to-120nT) on 1 June 2013 and its role in ring current ion transport and energization and plasmasphere erosion. During this storm, enhancements of similar to 1-2mV/m in the duskward electric field in the corotating frame are observed down to L shells as low as similar to 2.3. A simple model consisting of a dipole magnetic field and constant, azimuthally westward, electric field is used to calculate the earthward and westward drift of 90 degrees pitch angle ions. This model is applied to determine how far earthward ions can drift while remaining on Earth's nightside, given the strength and duration of the convection electric field. The calculation based on this simple model indicates that the enhanced duskward electric field is of sufficient intensity and duration to transport ions from a range of initial locations and initial energies characteristic of (though not observed by the Van Allen Probes) the earthward edge of the plasma sheet during active times (L similar to 6-10 and similar to 1-20keV) to the observed location of the 58-267keV ion population, chosen as representative of the ring current (L similar to 3.5-5.8). According to the model calculation, this transportation should be concurrent with an energization to the range observed, similar to 58-267keV. Clear coincidence between the electric field enhancement and both plasmasphere erosion and ring current ion (58-267keV) pressure enhancements are presented. We show for the first time nearly simultaneous enhancements in the duskward convection electric field, plasmasphere erosion, and increased pressure of 58-267keV ring current ions. These 58-267keV ions have energies that are consistent with what they are expected to pick up by gradient B drifting across the electric field. These observations strongly suggest that we are observing the electric field that energizes the ions and produces the erosion of the plasmasphere.
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- 2015
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8. Fine structure of large-amplitude chorus wave packets
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Scott R. Bounds, George Hospodarsky, Craig Kletzing, William S. Kurth, and Ondrej Santolik
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Physics ,biology ,Wave packet ,Acoustics ,Chorus ,biology.organism_classification ,Magnetic field ,Computational physics ,Acceleration ,symbols.namesake ,Geophysics ,Amplitude ,Van Allen radiation belt ,symbols ,General Earth and Planetary Sciences ,Waveform ,Van Allen Probes - Abstract
Whistler mode chorus waves in the outer Van Allen belt can have consequences for acceleration of relativistic electrons through wave-particle interactions. New multicomponent waveform measurements have been collected by the Van Allen Probes Electric and Magnetic Field Instrument Suite and Integrated Science's Waves instrument. We detect fine structure of chorus elements with peak instantaneous amplitudes of a few hundred picotesla but exceptionally reaching up to 3 nT, i.e., more than 1% of the background magnetic field. The wave vector direction turns by a few tens of degrees within a single chorus element but also within its subpackets. Our analysis of a significant number of subpackets embedded in rising frequency elements shows that amplitudes of their peaks tend to decrease with frequency. The wave vector is quasi-parallel to the background magnetic field for large-amplitude subpackets, while it turns away from this direction when the amplitudes are weaker.
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- 2014
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9. Electric Field, Magnetic Field, and Density Measurements on the Active Plasma Experiment Sounding Rocket
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J. I. Zetzer, Scott R. Bounds, B. G. Gavrilov, Henry Freudenreich, Robert E. Erlandson, Cheng I. Meng, Peter A. Delamere, and Robert F. Pfaff
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Physics ,Aerospace Engineering ,Magnetosonic wave ,Dipole model of the Earth's magnetic field ,Optical field ,Lower hybrid oscillation ,Computational physics ,L-shell ,Magnetic field ,Nuclear magnetic resonance ,Physics::Plasma Physics ,Space and Planetary Science ,Electric field ,Physics::Space Physics ,Magnetic pressure - Abstract
High-resolution, in situ measurements of dc and wave electric fields, magnetic fields, and plasma number density have been gathered by instruments on a diagnostic payload at which a high-velocity, overdense aluminum ion beam was directed from a separate payload spaced 468 m away. The experiment, called the Active Plasma Physics Experiment, was carried out in the Earth's high-latitude ionosphere at 360-km altitude using a sounding rocket. The experimental data clearly show a large diamagnetic cavity with a 93 % depletion of the Earth's magnetic field within a narrowly confined ( 1.5 V/m perpendicular to the magnetic field were observed that represented both the E × B bulk plasma velocity and a magnetosonic wave, which preceded the arrival of the beam that was also evident in the AB magnetometer data. The electric field data also show the presence of electric fields parallel to the magnetic field, including a bipolar electric field signature presumably set up to ensure current continuity. Other plasma waves associated with the release include Alfven perturbations, intense broadband turbulence extending to frequencies beyond 1 MHz, whistler-mode electromagnetic emissions at the ambient O + lower hybrid frequency, and ion acoustic turbulence. The measurements provide a self-consistent picture of the electrodynamics surrounding a high-velocity, overdense ion beam released in the high-latitude ionosphere.
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- 2004
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10. The APEX north star experiment: observations of high-speed plasma jets injected perpendicular to the magnetic field
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C.-I. Meng, J. I. Zetzer, Scott R. Bounds, Yu. N. Kiselev, Nikos Gatsonis, R. F. Pfaff, B. J. Stoyanov, P. K. Swaminathan, Hans C. Stenbaek-Nielsen, C. K. Kumar, K. A. Lynch, Robert E. Erlandson, B. G. Gavrilov, Virendra K. Dogra, and Peter Delamere
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Physics ,Atmospheric Science ,Astrophysics::High Energy Astrophysical Phenomena ,Nozzle ,Aerospace Engineering ,Magnetosphere ,Astronomy and Astrophysics ,Plasma ,Atmospheric sciences ,Magnetic field ,Computational physics ,Photometry (astronomy) ,Geophysics ,Physics::Plasma Physics ,Space and Planetary Science ,Ionization ,Physics::Space Physics ,General Earth and Planetary Sciences ,Optical radiation ,Ionosphere - Abstract
Initial results from the Active Plasma EXperiment North Star experiment are presented. The North Star active experiment included two separate plasma jet injections, both perpendicular to the Earth's magnetic field. The objective of the experiment is to investigate the interaction of high-speed (7–40 km/s) plasma jets with the ionospheric plasma and the coupling to the magnetosphere and lower ionosphere. The plasma jets were produced using an Explosive Type Generator device. This device is a shaped-charge device that vaporizes porous aluminum inside the generator and forces the vaporized products out of a nozzle, resulting in the production of a high-speed, partially ionized aluminum plasma jet. Instrumentation on three different payloads was used to obtain multi-point observations of the plasma jet properties, optical radiation from the jets, and ionospheric perturbations. Imagery, high-speed photometry, and spectrographic imagery using ground- and space-based sensors were used to monitor the dynamics and spectral content of the plasma jet. This paper describes the experiment and summarizes the initial results from the North Star experiment.
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- 2002
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11. Observations in the E region ionosphere of kappa distribution functions associated with precipitating auroral electrons and discrete aurorae
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Craig Kletzing, Michael J. Nicolls, Scott R. Bounds, S. R. Kaeppler, and A. Stromme
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Physics ,Sounding rocket ,Plasma sheet ,Electron precipitation ,Electron ,Geophysics ,Computational physics ,Latitude ,Distribution function ,Physics::Plasma Physics ,Space and Planetary Science ,Physics::Space Physics ,Kappa distribution ,Ionosphere - Abstract
Precipitating auroral electrons can produce discrete auroral arcs that contain signatures of the magnetospheric auroral source region. Differential number flux observations over two discrete aurorae were obtained by the Auroral Currents and Electrodynamics Structure sounding rocket mission, which successfully launched in 2009. These observations were made at E region altitudes of approximately 130 km. A model of precipitating auroral electrons as described by Evans (1974) was fit to the electron differential number flux obtained by the payloads, and parameters from the model were used to infer properties of the auroral source region. It is shown that the field-aligned precipitating electrons were better fit by a kappa distribution function versus a Maxwellian distribution function for the equatorward side of the first, quasi-stable, auroral arc crossing. The latter half of the first auroral arc crossing and second auroral crossing show that the precipitating electrons were better fit by a Maxwellian distribution function, which provides additional observational confirmation of previous studies. The low-energy electron population determined by the Evans (1974) model was within a factor of 2 of the observed differential number flux. The source region parameters determined from fitting the model to the data were compared with relevant studies from sounding rockets and satellites. Our observations are consistent with the results of Kletzing et al. (2003) that the plasma sheet electrons mapping to auroral zone invariant latitudes are characterized by kappa distribution functions.
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- 2014
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12. Strong magnetic field fluctuations within filamentary auroral density cavities interpreted as VLF saucer sources
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Scott R. Bounds, D. D. Wallis, D. L. Knudsen, R. Kabirzadeh, Robert F. Pfaff, Jean-Louis Pinçon, J. K. Burchill, J. H. Clemmons, NASA Goddard Space Flight Center (GSFC), Department of Physics and Astronomy [Calgary], University of Calgary, Department of Electrical Engineering [Stanford], Stanford University, Natural Resources Canada (NRCan), Department of Physics and Astronomy [Iowa City], University of Iowa [Iowa City], The Aerospace Corporation, Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), and GEODESIC project was provided by the Canadian Space Agency and NASANatural Sciences and Engineering Research Council of Canada, and by NASA grant NAG5-5201
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Atmospheric Science ,Hiss ,010504 meteorology & atmospheric sciences ,Soil Science ,Electron precipitation ,Aquatic Science ,Oceanography ,01 natural sciences ,7. Clean energy ,Physics::Geophysics ,Geochemistry and Petrology ,Electric field ,0103 physical sciences ,Substorm ,Earth and Planetary Sciences (miscellaneous) ,010306 general physics ,0105 earth and related environmental sciences ,Earth-Surface Processes ,Water Science and Technology ,Physics ,Sounding rocket ,Ecology ,Paleontology ,Forestry ,Plasma ,Geophysics ,Magnetic field ,Computational physics ,Earth's magnetic field ,[SDU]Sciences of the Universe [physics] ,13. Climate action ,Space and Planetary Science ,Physics::Space Physics - Abstract
International audience; [1] The Geoelectrodynamics and Electro-Optical Detection of Electron and Suprathermal Ion Currents (GEODESIC) sounding rocket encountered more than 100 filamentary density cavities associated with enhanced plasma waves at ELF (
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- 2012
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13. Auroral electron dispersion below inverted-V energies: Resonant deceleration and acceleration by Alfvén waves
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Shuanghui Hu, Li-Jen Chen, Scott R. Bounds, and Craig Kletzing
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Physics ,Atmospheric Science ,Ecology ,Wave propagation ,Paleontology ,Soil Science ,Electron precipitation ,Forestry ,Electron ,Aquatic Science ,Oceanography ,Computational physics ,Alfvén wave ,Geophysics ,Amplitude ,Space and Planetary Science ,Geochemistry and Petrology ,Electric field ,Physics::Space Physics ,Earth and Planetary Sciences (miscellaneous) ,Electromagnetic electron wave ,Atomic physics ,Dispersion (water waves) ,Earth-Surface Processes ,Water Science and Technology - Abstract
[1] Rocket observations of electron time dispersion which occurs at energies below the primary inverted-V electron precipitation exhibit a variety of characteristics in the dispersion timescale and flux intensity distribution. We present simulation results that illustrate how different dispersion signatures can be produced by resonant acceleration and deceleration of auroral electrons by inertial Alfven waves. We investigate the individual effects of relevant parameters such as the altitude of the inverted-V potential, Alfven wave amplitude, wave velocity, and source electron population. The energies to which Alfven waves can accelerate electrons are primarily determined by the peak Alfven speed below the DC potential drop and to a lesser extent by the amplitude of the wave parallel electric field. The observed electron signatures can be used to obtain information about the peak Alfven speed, the wave parallel electric field, the DC electric field, and plasma environment through which the waves propagate.
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- 2005
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14. Rocket observations of structured upper hybrid waves at f uh = 2f ce
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M. Samara, Craig Kletzing, Scott R. Bounds, and James LaBelle
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Physics ,business.product_category ,business.industry ,Cyclotron ,Electron ,Instability ,law.invention ,Computational physics ,Geophysics ,Optics ,Altitude ,Rocket ,law ,Harmonic ,General Earth and Planetary Sciences ,business ,Electronic band structure ,Electron distribution - Abstract
[1] The HIgh Bandwidth Auroral Rocket (HIBAR), launched into active pre-midnight aurora, encountered two bursts of 2–10 mV/m upper hybrid waves just below fuh = 2fce at approximately 377 and 390 km altitude. These waves occur in association with a density “shoulder” and enhancement, respectively. The waves show several bands of frequency structure with 4–8 kHz spacings and, within these, bands of frequency sub structure with 1–2 kHz spacings. At the time of the waves, the measured electron distribution indicates wave instability for frequencies 1–1.2% percent below the electron cyclotron harmonic. These results agree qualitatively with theoretical work predicting banded structure associated with upper hybrid waves trapped in density enhancements.
- Published
- 2004
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