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Results for “ELECTRON SPECTRA”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1998

Radial Distribution of Electron Spectra from High-Energy Ions

The average track model describes the response of physical and biological systems using radial dose distribution as the key physical descriptor. We report on an extension of this model to describe the average distribution of electron spectra as a function of radial distance from an ion. We present calculations of these spectra for ions of identical linear energy transfer (LET), but dissimilar charge and velocity to evaluate the differences in electron spectra from these ions. To illustrate the usefulness of the radial electron spectra for describing effects that are not described by electron dose, we consider the evaluation of the indirect events in microdosimetric distributions for ions. We show that folding our average electron spectra model with experimentally determined frequency distributions for photons or electrons provides a good representation of radial event spectra from high-energy ions in 0.5-2 micrometer sites.

Cucinotta, Francis A.↗
NASA NTRS2003

Electron Bremsstrahlung Hard X-Ray Spectra, Electron Distributions and Energetics in the 2002 July 23 Solar Flare

We present and analyze the first high-resolution hard X-ray spectra from a solar flare observed in both X-ray/gamma-ray continuum and gamma-ray lines. The 2002 July 23 flare was observed by the Ramaty High Energy Solar Spectroscopic Imager (RHESSI). The spatially integrated photon flux spectra are well fitted between 10 and 300 keV by the combination of an isothermal component and a double power law. The flare plasma temperature peaks at 40 MK around the time of peak hard X-ray emission and remains above 20 MK 37 min later. We derive the evolution of the nonthermal mean electron flux distribution by directly fitting the RHESSI X-ray spectra with the thin-target bremsstrahlung from a double power-law electron distribution with a low-energy cutoff. We also derive the evolution of the electron flux distribution on the assumption that the emission is thick-target bremsstrahlung. We find that the injected nonthermal electrons are well described throughout the flare by this double power-law distribution with a low-energy cutoff that is typically between 20 - 40 keV. Using our thick-target results, we compare the energy contained in the nonthermal electrons with the energy content of the thermal flare plasma observed by RHESSI and GOES. We find that the minimum total energy deposited into the flare plasma by nonthermal electrons, 2.6 x 10(exp 31) erg, is on the order of and possibly less than the energy in the thermal plasma. However, these fits do not rule out the possibility that the energy in nonthermal electrons exceeds the energy in the thermal plasma. This work was supported in part by the RHESSI Project and the NASA Sun-Earth Connection program.

Holman, G. D.↗
NASA NTRS2003

Electron Bremsstrahlung Hard X-Ray Spectra, Electron Distributions and Energetics in the 2002 July 23 Solar Flare

We present and analyze the first high-resolution hard X-ray spectra from a solar flare observed in both X-ray/gamma-ray continuum and gamma-ray lines. The 2002 July 23 flare was observed by the Ramaty High Energy Solar Spectroscopic Imager (RHESSI). The spatially integrated photon flux spectra are well fitted between 10 and 300 keV by the combination of an isothermal component and a double power law. The flare plasma temperature peaks at 40 MK around the time of peak hard X-ray emission and remains above 20 MK 37 min later. We derive the evolution of the nonthermal mean electron flux distribution by directly fitting the RHESSI X-ray spectra with the thin-target bremsstrahlung from a double power-law electron distribution with a low-energy cutoff. We also derive the evolution of the electron flux distribution on the assumption that the emission is thick-target bremsstrahlung. We find that the injected nonthermal electrons are well described throughout the flare by this double power-law distribution with a low-energy cutoff that is typically between 20-40 keV. Using our thick-target results, we compare the energy contained in the nonthermal electrons with the energy content of the thermal flare plasma observed by RHESSI and GOES. We find that the minimum total energy deposited into the flare plasma by nonthermal electrons, 2.6 x 10(exp 31)erg, is on the order of and possibly less than the energy in the thermal plasma. However, these fits do not rule out the possibility that the energy in nonthermal electrons exceeds the energy in the thermal plasma.

Holman, Gordon D.↗
NASA NTRS1983

Complex time dependent wave packet technique for thermal equilibrium systems - Electronic spectra

A time dependent wave packet method is presented for the rapid calculation of the properties of systems in thermal equilibrium and is applied, as an illustration, to electronic spectra. The thawed Gaussian approximation to quantum wave packet dynamics combined with evaluation of the density matrix operator by imaginary time propagation is shown to give exact electronic spectra for harmonic potentials and excellent results for both a Morse potential and for the band contours of the three transitions of the visible electronic absorption spectrum of the iodine molecule. The method, in principle, can be extended to many atoms (e.g., condensed phases) and to other properties (e.g., infrared and Raman spectra and thermodynamic variables).

Reimers, J. R.↗
NASA NTRS1987

The electronic spectra of mu-peroxodicobalt(III) complexes

Problems found in the determination of the electronic spectra of mu-peroxodicobalt(III) complexes are considered, and the common formation of different mu-peroxocomplexes upon oxygenation of Co(II)-ligand solutions is discussed. Three classes of spectra have been identified: (1) planar single bridged complexes; (2) nonplanar single-bridged complexes with a dihedral angle near 145 deg; and (3) dibridged mu-OH(-),O2(2-) complexes with a dihedral angle near 60 deg. All of the peroxide ligand-to-metal charge-transfer spectra are found to be consistent with a simple model that assumes a sinusoidal dependence of pi-asterisk O2(2-) energies and sigma-overlaps upon the dihedral angle.

Miskowski, Vincent M.↗
NASA NTRS1989

Characteristics of energetic solar flare electron spectra

A 55 event survey of energy spectra of 0.1-100 MeV interplanetary electrons originating from solar flares as measured by two spectrometers onboard the ISEE 3 (ICE) spacecraft for the years 1978-1982 has been completed. Spectra generated using the maximum flux of a given event in each energy channel were restricted to events with a well-defined flux rise time. Two broad groups of electron spectra are considered. In one group, the spectra are well represented by a single power law in rigidity with spectral index in the range 3-4.5. The spectra in the other group deviate from a power law in rigidity systematically in that they harden with increasing rigidity. Events with near power-law spectra are found to be correlated with long-duration soft X-ray events, whereas those with hardening spectra are correlated with short-duration events. The possible variation of acceleration and propagation processes with the properties of the flare site is discussed, using the duration of the soft X-ray flare emission as an indicator of the physical parameters of the flare site (flare volume, density, coronal height, and magnetic field geometry).

Moses, Dan↗
NASA NTRS1973

Auroral electron spectra

Discussion of the suitability of available differential electron flux data for auroral analyses. The differential energy spectra of auroral electrons at several altitudes computed by Berger et al. (1973) and Rees and Jones (1973) for initial electron energies of 10, 5, and 2 keV are reviewed, and it is concluded that they are suitable for auroral analyses.

Rees, M. H.↗
NASA NTRS1992

The derivation of parent electron spectra from bremsstrahlung hard X-ray spectra

A numerical method is formulated to derive the spectrum of the parent electrons from the hard X-ray spectrum produced in optically thin bremsstrahlung. The method can utilize any form for the bremsstrahlung cross sections, and it provides accurate estimates of uncertainties in the derived electron spectrum based on uncertainties in the photon measurements. This method is applied to test photon spectra, as well as to hard X-ray spectra of the June 27, 1980 solar flare which was observed by high spectral resolution detectors. Future measurements with much more sensitive detectors will enable this method to be used to derive detailed, accurate flare electron spectra.

Johns, Christopher M.↗
NASA NTRS1973

A study of cosmic-ray positron and electron spectra in interplanetary and interstellar space and the solar modulation of cosmic rays

The differential energy spectra of cosmic-ray positrons and negatrons with energies between approximately 11 and 1500 MeV was measured during the period 1968-1971 using a balloon-borne magnetic spectrometer. These measurements fill a gap in the previously existing data and permit the determination of the interstellar spectra of cosmic-ray positrons and electrons. Knowledge of these spectra provides a crucial tool for studies of the distribution and density of matter and magnetic fields in the interstellar medium and the origin and dynamics of energetic particles contained in the fields. The differential energy spectrum of interstellar electrons may be represented as a power-law, j alpha T to the -1.8 power for 100 MeV approximately T approximately 2 GeV, but must flatten considerably at lower energies. From the measured electron charge composition, it is concluded that the majority of cosmic-ray electrons with energies above approximately 10 MeV originate in primary sources.

Cummings, A. C.↗
NASA NTRS1977

Correlation of ground-based and topside photometric observations with auroral electron spectra measurements at rocket altitudes

Data are collected by electron detectors aboard a sounding rocket measuring the primary electron spectrum and the energy flux on the field lines containing auroral light in the E region. These data are compared to calculations based on spectroscopic measurements of the auroral lines 4278, 5577, and 6300 A used in predicting the energy influx and the characteristic energy of an assumed Maxwellian primary electron spectrum for two auroral displays. Data were also collected by photometers sampling the auroral light from the E region magnetically conjugate to the rocket. These data are compared to those of current ionospheric models.

Arnoldy, R. L.↗
NASA NTRS1986

Angle-resolved Auger electron spectra induced by neon ion impact on aluminum

Auger electron emission from aluminum bombarded with 1 to 5 keV neon ions was studied by angle-resolved electron spectroscopy. The position and shape of the spectral features depended on the incident ion energy, angle of ion incidence, and electron take-off angle with respect to the aluminum surface. These spectral dependencies were interpreted in terms of the Doppler shift given to the Auger electron velocity by the excited atom ejected into the vacuum. For oblique ion incidence it is concluded that a flux of high energy atoms are ejected in a direction close to the projection of the ion beam on the target surface. In addition, a new spectral feature was found and identified as due to Auger emission from excited neon in the aluminum matrix.

Pepper, S. V.↗
NASA NTRS1985

The electron spectra in the synchrotron nebula of the supernova remnant G 29.7-0.3

EXOSAT results obtained with the imaging instrument (CMA) and the medium energy proportional counters (ME) are discussed. Assuming that the featureless power-law spectrum obtained in the 2 to 10 keV range is synchrotron radiation from relativistic electrons, one derives constraints on magnetic field strength and age of the nebula. The energy spectra of the electrons responsible for the emission in the radio and X-ray ranges are discussed. The great similarity of the physical properties of G 29.7-0.3 and of three synchrotron nebulae containing a compact object observed to pulse in X-rays makes G 29.7 - 0.3 a very promising candidate for further search for pulsed emission. Further observations at infrared wavelengths might reveal the break(s) in the emitted spectrum expected from the radio and X-ray power-law indices and give us more information on the production of the electron populations responsible for the emission of the nebula.

Koch-Miramond, L.↗