Angular distributions, kinetic energy distributions, and excitation functions of fast metastable oxygen fragments following electron impact on CO2
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Misakian, M.↗
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Basic factors for acquiring, correcting, and interpreting probe current-voltage characteristic in moderate-collisional plasma for determining electron energy distribution
Methods for inferring the electron distribution function (EDF) from a probe current–voltage trace are reviewed for moderate-collisional plasma. The explicit accounting of particle collisions, modeling sheath depletion, and electron refilling processes are rarely performed when analyzing probe measurements, yet they are critical for regime validity, EDF-profile accuracy, and space potential quantification precision. Furthermore, the advantages, limitations, and utilization of large-area wall probes in moderate-collisional plasma, capable of highly resolved indications of energetic electrons in plasma, are outlined.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
A theory of local and global processes which affect solar wind electrons. I - The origin of typical 1 AU velocity distribution functions - Steady state theory
A kinetic theory for the velocity distribution of solar wind electrons which illustrates the global and local properties of the solar wind expansion is proposed. By means of the Boltzmann equation with the Krook collision operator accounting for Coulomb collisions, it is found that Coulomb collisions determine the population and shape of the electron distribution function in both the thermal and suprathermal energy regimes. For suprathermal electrons, the cumulative effects of Coulomb interactions are shown to take place on the scale of the heliosphere itself, whereas the Coulomb interactions of thermal electrons occur on a local scale near the point of observation (1 AU). The bifurcation of the electron distribution between thermal and suprathermal electrons is localized to the deep solar corona (1 to 10 solar radii).
Scudder, J. D.↗
Calculations of longitude dependence of geomagnetically trpped electron fluxes. part i- the general fokker-planck equation for electron diffusion
General Fokker-Planck equation for geomagnetically trapped electron distribution as function of longitude, time, energy, and mirror point field intensity
ELECTRON DISTRIBUTION↗
Characteristics of electron velocity distribution functions in the solar wind derived from the Helios plasma experiment
The details of the shapes of three typical electron distribution functions observed by the Helios 1 and 2 probes in the solar wind between 0.3 AU and 1 AU are analyzed and compared with theoretical predictions. These are (1) a distribution function with a narrow 'strahl' (narrow beam), which is extremely anisotropic and skewed with respect to the magnetic field direction at particle energies above 100 eV; (2) a distribution function with a broad 'strahl', less anisotropic and skewed; and (3) a nearly isotropic distribution function. For each distribution function, a sudden change in the slope was discerned, separating the 'core' at lower energies from the 'halo' at higher energies. The most obvious differences of the analyzed electron distribution functions were observed at energies above 50-100 eV. The possible origins for the observed features of the distribution functions are discussed.
Pilipp, W. G.↗
Characterization and Optimization of the Fitting of Quantum Correlation Functions
This case study presents a characterization and optimization of an application code for extracting parton distribution functions from high energy electron-proton scattering data. Profiling this application code reveals that the phase-space density computation accounts for 93% of the overall execution time for a single iteration on a single core. When executing multiple iterations in parallel on a multicore system, the application spends 78% of its overall execution time idling due to load imbalance. We address these issues by first transforming the application code from Python to C++ and then tackling the application load imbalance via a hybrid scheduling strategy that combines dynamic and static scheduling. These techniques result in a 62% reduction in CPU idle time and a 2.46x speedup in overall execution time per node. In addition, the typically enabled power-management mechanisms in supercomputers (e.g., AMD Turbo Core, Intel Turbo Boost, and RAPL) can significantly impact intra-node scalability when more than 50% of the CPU cores are used. This finding underscores the importance of understanding system interactions with power management, as they can adversely impact application performance, and highlights the necessity of intra-node scaling tests to identify performance degradation that inter-node scaling tests might otherwise overlook.
Chuang, Pi-Yueh [Virginia Tech,Dept. of Computer S↗
Calculations of longitude dependence of geomagnetically trapped electron fluxes. i - the general fokker-planck equation for electron diffusion.
Fokker-Planck equation for geomagnetically trapped electron distribution as function of longitude, time, energy and mirror-point field intensity
GEOMAGNETICALLY TRAPPED PARTICLE↗
Theoretical description of trapped electron diffusion in the South American anomaly.
Fokker-Planck equation for geomagnetically trapped electron distribution as function of longitude, time, energy and mirror-point field intensity
GEOMAGNETICALLY TRAPPED PARTICLE↗
Auroral Microphysics Rocket (AMICIST) and Reflight of the Phaze Sounding Rocket
This grant was originally awarded for the flight of the AMICIST sounding rocket. However, upon launch failure of the PHAZE rocket, additional resources were placed in this grant to cover the launch of the PHAZE II rocket. AMICIST was successfully launched from the Poker Flat Range on February 24, 1995, and the PHAZE II was successfully launched also from the Poker Flat Range on February 10, 1997. The major objective of the AMICIST flight was to investigate the bursts of transverse ion acceleration occurring during aurora, commonly known as Lower Hybrid Solitary Structures, with the flight of two scientific payloads to unravel space from time effects. The data clearly showed that the structures of ion acceleration were a spatial phenomena having a scale size transverse to the local magnetic field of about 100 m. On the other hand, structures in the auroral electrons were generally observed on this flight to be temporal features that occurred at the same time at the two payloads separated by a few kilometers. The primary objective of the PHAZE rocket flight was to further study the temporal features of auroral electron precipitation having many electron detectors, some fixed in energy, that could study the distribution function of the auroral electrons on time scales of a fraction of a millisecond. A important paper on this topic has just been submitted for publication which uses the PHAZE data to show that the potential structure (electric field parallel to the magnetic field) that accelerates the auroral electrons within one Earth radius of the ground, is not static, but rather fluctuates with frequencies close to the local proton and hydrogen gyrofrequencies. The fluctuation appears to be an actual turning on and off of the electric field at these frequencies. When the potential is turned off, ambient electrons can enter the region and be accelerated along B when the potential is on creating field- aligned bursts which manifest themselves as flickering aurora seen from the ground. The on/off model can explain many of the dynamic features of the aurora which have been unexplained since man first looked up at the visual display. Much needs to be done yet to understand how ions couple into this process.
Arnoldy Roger L.↗
The quasi-linear relaxation of thick-target electron beams in solar flares
The effects of quasi-linear interactions on thick-target electron beams in the solar corona are investigated. Coulomb collisions produce regions of positive gradient in electron distributions which are initially monotonic decreasing functions of energy. In the resulting two-stream instability, energy and momentum are transferred from electrons to Langmuir waves and the region of positive slope in the electron distribution is replaced by a plateau. In the corona, the timescale for this quasi-linear relaxation is very short compared to the collision time. It is therefore possible to model the effects of quasi-linear relaxation by replacing any region of positive slop in the distribution by a plateau at each time step, in such a way as to conserve particle number. The X-ray bremsstrahlung and collisional heating rate produced by a relaxed beam are evaluated. Although the analysis is strictly steady state, it is relevant to the theoretical interpretation of hard X-ray bursts with durations of the order of a few seconds (i.e., the majority of such bursts).
Mcclements, K. G.↗
Impulsive phase of solar flares. 1: Characteristics of high energy electrons
The variation along a magnetic field line of the energy and pitch angle distribution of high energy electrons injected into a cold hydrogen plasma containing either an open or closed magnetic field structure was investigated. The problem is formulated as a time independent Fokker-Planck Equation for the electron number distribution as a function of the electron energy, electron pitch angle, and the structure of the global magnetic field. Simple analytic solution valid in the small pitch angle regime and for slowly varying magnetic field is presented. For the more general situation a numerical code for solving the Fokker-Planck Equation was used and it was found that the analytic expression agrees well with the numerical results to values of the pitch angle much larger than expected. For most practical applications, one many confidently use the analytic expression instead of having to resort to lengthy numerical computations. These results are useful in the study of the nonthermal models of the impulsive phase of solar flares.
Leach, J.↗
Nonlinear energy flow in a beam-plasma system
The three-dimensional character of the beam-plasma instability is investigated. The true beam-electron distribution function is resolved with a novel directional energy analyzer. The electron plasma waves are observed to develop a large spread in perpendicular wave numbers and damp in a relatively short distance producing an energetic electron tail on the background distribution. The damping is believed to be due to strong ion fluctuations which produce an anomalous resistivity.
Whelan, D. A.↗
Probe and radar electron temperatures in an isotropic nonequilibrium plasma.
Electron temperatures measured by electrostatic probes and radar backscatter are distinct physical quantities, the temperature from each technique determined from a different moment of the electron-distribution function. Numerical inequality of temperatures results from a non-Maxwellian electron-distribution function or, equivalently, from a nonequilibrium electron plasma. Probe and backscatter electron temperatures are studied for low- and high-energy (isotropic) distortions of the distribution function. The nonequilibrium plasma generally produces higher probe than backscatter temperatures; however, the temperature difference is small for distortions due to realistic photoelectron populations. If the ionosphere is in a highly nonequilibrium state, probe and backscatter temperatures would differ from the temperature characterizing the average electron kinetic energy, and a single temperature applicable to a variety of physical processes would no longer exist.
Hoegy, W. R.↗
Electron transport and energy degradation in the ionosphere: Evaluation of the numerical solution, comparison with laboratory experiments and auroral observations
Auroral electron transport calculations are a critical part of auroral models. We evaluate a numerical solution to the transport and energy degradation problem. The numerical solution is verified by reproducing simplified problems to which analytic solutions exist, internal self-consistency tests, comparison with laboratory experiments of electron beams penetrating a collision chamber, and by comparison with auroral observations, particularly the emission ratio of the N2 second positive to N2(+) first negative emissions. Our numerical solutions agree with range measurements in collision chambers. The calculated N(2)2P to N2(+)1N emission ratio is independent of the spectral characteristics of the incident electrons, and agrees with the value observed in aurora. Using different sets of energy loss cross sections and different functions to describe the energy distribution of secondary electrons that emerge from ionization collisions, we discuss the uncertainties of the solutions to the electron transport equation resulting from the uncertainties of these input parameters.
Lummerzheim, D.↗
Measurements by the plasma diagnostics package on STS-3
A comprehensive set of measurements about the orbiter environment are provided by the plasma diagnostics package (PDP). Ion and electron particle densities, energies, and spatial distribution functions; ion mass for identification of particular molecular ion species; and magnetic fields, electric fields and electromagnetic waves over a broad frequency range are studied. Shuttle environmental measurements will be made both on the pallet and, by use of the remote manipulator system (RMS), the PDP will be maneuvered in and external to the bay area to continue environmental measurements and to carry on a joint plasma experiment with the Utah State University fast-pulsed electron generator. Results of orbiter environment EMI measurements and S-band field strengths as well as preliminary results from wake search operations indicating wake boundary identifiers are reported.
Shawhan, S. D.↗
Variations of electron distribution functions in the solar wind
Variations of electron distribution functions in the solar wind have been investigated using the electron data observed aboard Helios 2 during the first four months of its mission in 1976 in the distance range between 0.3 and 1 AU. In particular, variations across the sector structure of the interplanetary magnetic field and across the plasma stream structures have been studied. It has been found that there is a strong correlation between the electron properties and the sector structure of the magnetic field. Within the interior of magnetic sectors the electron distribution functions are extremely anisotropic and skewed with respect to the magnetic field direction at high particle energies. Toward sector boundaries the electron distribution functions become less anisotropic and less skewed. Right at sector boundaries the electrons are relatively cool, and their distributions are nearly isotropic often showing a slight bidirectional anisotropy. These observations have been interpreted to indicate that scattering of electrons with energies above 100 eV is weak within the interior of magnetic sectors but anomalous scattering increases drastically toward sector boundaries for all energies in the halo regime up to several hundred eV. There is evidence for closed magnetic field structures, probably occurring frequently in the solar wind, where the magnetic field lines should usually be connected to the sun outside sector boundaries but may or may not be disconnected from the sun at sector boundaries.
Pilipp, W. G.↗
A comparison of the radio data and model calculations of Jupiter's synchrotron radiation. I - The high energy electron distribution in Jupiter's inner magnetosphere. II - East-west asymmetry in the radiation belts as a function of Jovian longitude
A comparison has been made between detailed model calculations of Jupiter's synchrotron radiation and the radio data at wavelengths of 6, 21, and 50 cm. The calculations were performed for a Jovian longitude of 200 deg and were based on the multipole field configurations as derived from the Pioneer data. The electron distribution in the inner magnetosphere was derived as a function of energy, pitch angle, and spatial coordinates. In addition, the hot region or east-west asymmetry in the radiation belts is investigated. It is suggested that this asymmetry is due to the combined effect of an overabundance of electrons at jovicentric longitudes of 240-360 deg and the existence of a dusk-to-dawn directed electric field over the inner magnetosphere generated by the wind system in the upper atmosphere.
De Pater, I.↗
The composition of cosmic rays near the Bend (10 to the 15th power eV) from a study of muons in air showers at sea level
The distribution of muons near shower cores was studied at sea level at Fermilab using the E594 neutrino detector to sample the muon with E testing 3 GeV. These data are compared with detailed Monte Carlo simulations to derive conclusions about the composition of cosmic rays near the bend in the all particle spectrum. Monte Carlo simulations generating extensive air showers (EAS) with primary energy in excess of 50 TeV are described. Each shower record contains details of the electron lateral distribution and the muon and hadron lateral distributions as a function of energy, at the observation level of 100g/cm. The number of detected electrons and muons in each case was determined by a Poisson fluctuation of the number incident. The resultant predicted distribution of muons, electrons, the rate events are compared to those observed. Preliminary results on the rate favor a heavy primary dominated cosmic ray spectrum in energy range 50 to 1000 TeV.
Goodman, J. A.↗