Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “PARTICLE FLUX”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Cosmogenic neon from individual grains of CM meteorites - Extremely long pre-compaction exposure histories or an enhanced early particle flux

This paper presents the results on cosmogenic Ne extracted from individual meteoritic grains by a laser extraction system which used, at different times, two CW lasers: an Ar-ion laser and an Nd:YAG laser, with 20 and 70 W of deliverable power, respectively. Chemical etching was used to select grains exposed to solar flare VH particles. Results show that most of the grains with solar flare VH tracks (but not those which did not exhibit such tracks) contain spallation-produed Ne in significant excess of that due to the nominal cosmic-ray exposure, providing evidence for extensive energetic particle exposure during the precompaction era.

Hohenberg, Charles M.↗
NASA NTRS1976

A program of data synthesis from the ALSEP/CPLEE ALSEP/SIDE, and Explorer 35 magnetometer to investigate lunar terminator and nightside particle fluxes and surface interactions

Lunar nightside electron fluxes were studied with the aid of the ALSEP/CPLEE and other instruments. The flux events were shown to be due to (a) electrons propagating upstream from the earth's bow shock, (b) electrons thermalized and scattered to the lunar surface by disturbances along the boundary of the lunar solarwind cavity, and (c) solar wind electrons scattered to the lunar surface by lunar limb shocks and/or compressional disturbances. These electrons were identified as a cause of the high night surface negative potentials observed in tha ALSEP/SIDE ion data. A study was also made of the shadowing of magnetotail plasma sheet electrons by interactions between the lunar body and the ambient magnetic field and by interactions between charged particles and lunar remnant magnetic fields. These shadowing effects were shown to modify lunar surface and near-lunar potential distributions.

Reasoner, D. L.↗
NASA NTRS1972

Analysis of auroral particle fluxes

The physical processes which describe the interaction of auroral electrons with the atmosphere appear to be more complex than just the Coulomb scattering of the incident primary electrons with a subsequent loss of energy. The comparison of the measured backscattered electron spectra with spectra predicted using a theoretical scattering calculation has led to a discrepancy for energies below about 1 to 2 keV. It was found that the very high ratio (100%) of backscattered to incident fluxes for these energies could be most reasonably explained by a parallel downward-directed electric field which prevents these lower energy electrons from entering the atmospheric scattering region. This parallel field with potential drop of about 1 keV is thought to have its origin in waveparticle interactions in the turbulent auroral ionosphere.

Chappell, C. R.↗
NASA NTRS1972

Energetic particle flux experiment (IMP-F and G)

The technical aspects of the University of California IMP-F experiment aboard the Explorer-34 and the University of California IMP-G (S1) and (S2) experiments aboard the Explorer-41. The experiment detectors and electronics are discussed for each experiment as well as the fabrication, preflight and post-flight history. A description of the ground support equipment is also given for each experiment. These three experiments were essentially all different. The IMP-G experiment was essentially the IMP-F experiment with the addition of four Geiger-Mueller detectors. The IMP-G (S-2) was a supplementary experiment and differed completely from the IMP-F and IMP-G experiments. It was concluded that the ground support equipment approach used for the IMP-F and IMP-G experiments where emphasis was placed on a thorough exercise and monitoring of the experiment operation during various testing phases provided a high degree of confidence and reliability in these experiments. No known electronic failures have occurred during the spacecraft lifetime although some detector problems were experienced.

Anderson, K. A.↗
NASA NTRS1973

Analysis of auroral particle fluxes

The study is reported of electron and proton precipitation in different auroral forms from data obtained by the TWINS 1 and 2. The measurement of the energy spectra and pitch angle distributions of auroral electrons is discussed along with the auroral electron code for predicting the scattering and energy loss of electrons covering the complete auroral energy spectrum.

Chappell, C. R.↗
NASA NTRS1975

A reinterpretation of the reported energetic particle fluxes in the vicinity of Mercury

During the Mercury flyby of Mariner 10, observations of large fluxes of energetic electrons (energies in excess of 0.3 MeV) and protons (energies between 0.53 and 1.9 MeV) were reported by Simpson et al. (1974). The reported simultaneous enhancements of protons and electrons in the magnetic field of Mercury have raised some perplexing planetology questions. It is shown here that the response of the proton detector in the Mariner 10 experiment is most plausibly attributable to the pileup of low-energy electrons rather than the presence of protons in the vicinity of Mercury. Further, the reported lower-limit electron differential spectrum exponent of at least 9 and the 300-keV electron fluxes are probably in quantitative error, especially where the count rates are highest. It is concluded that no 'new' acceleration mechanism has been identified at Mercury.

Armstrong, T. P.↗
NASA NTRS1976

Simultaneous observations of field-aligned currents and particle fluxes in the post-midnight sector

The paper presents several examples of simultaneous measurements of electrons and positive ions (5 eV to 15 eV) and of magnetic field perturbations due to field-aligned currents made on the polar-orbiting ISIS-2 satellite at 1400 km altitude in the early morning local time (MLT) sector. There is a good general correspondence between changes in the gradient of the E-W component of the magnetic field along the spacecraft orbit and changes in the character of the low-energy electron fluxes. The equatorward region of outward current flow in this post-midnight sector is spatially coincident with the isotropic precipitation associated with the low-altitude plasma sheet. In cases examined, electron current density always exceeds positive ion current density by a factor of 10 and usually by a factor of over 100.

Klumpar, D. M.↗
NASA NTRS1979

On the phase relationship between the energetic particle flux modulation and current disc penetrations in the Jovian magnetosphere - Pioneer 10 inbound

The surface defined by the locus of field minima along field lines for an unterminated Jovian model magnetosphere is found to coincide with the surface of the model current disk which provides a good fit to the data. However, when the model is terminated by means of magnetopause currents, preservation of the fit by modifying the current distribution near the outer edge of the disk causes the minimum absolute magnetic field surface to bifurcate. Energetic electron flux time profiles that are based upon such a minimum absolute magnetic field configuration are found to be qualitatively consistent with the inbound Pioneer 10 data.

Jones, D. E.↗
NASA NTRS1985

Study of the time-differentiated particle flux density at various distances from EAS axis

The EAS time structure is studied using the enlarged EAS array of the Moscow State University. The time measurements are made using 22 scintillators which form 13 rectanges of 180x190 sq m size covering the entire array area. The array is triggered by a signal of 4-fold coincidences of the pulses from the detectors forming each of the rectangles. The data were obtained during 2200 hours of the array operation in 1984. A total of 816 showers, to which at least 14 of 22 scintillator detectors responded, were selected among all those detected. The coordinates of the EAS axis in the observation plane and the EAS sizes were determined by the maximum likelihood method using a computer on the assumption that the electron LDF is the NKG form. A total of 492 showers in the interval of EAS size Ne = 5x10 to the 6th power - 2x10 to the 8th power (N bar e = 1.7x 10 to the 7th power) with zenith angles theta or = 45 deg and axes within the array are analyzed.

Atrashkevich, V. G.↗
NASA NTRS1989

The neutral E region zonal winds during intense postmidnight diffuse aurora - Response to observed particle fluxes

Zonal winds associated with diffuse auroras were simulated using observed fluxes of electron precipitation and a high-resolution time-dependent numerical model described by Waltershcheid et al. (1985). A very strong dynamically unstable E region jet is simulated for an electric field of 50 mV/m, and the results suggest a connection with omega band. These zonal winds are not as strong as those reported by Lyons and Walterscheid (1985), but are much stronger (by a factor of 3 or greater) than the E region winds simulated by Fuller-Rowell (1985). The effects of large-scale cross-arc winds were simulated to evaluate their effect; it is shown that strong cross-arc winds are required to prevent the formation of a strong E zonal jet. The results agree qualitatively with radar observations of zonal winds by Johnson et al. (1987).

Walterscheid, R. L.↗
NASA NTRS2016

Stair-Step Particle Flux Spectra on the Lunar Surface: Evidence for Nonmonotonic Potentials?

We present examples of unusual "stair‐step" differential flux spectra observed by the Apollo 14 Suprathermal Ion Detector Experiment on the lunar dayside surface in Earth's magnetotail. These spectra exhibit a relatively constant differential flux below some cutoff energy and then drop off precipitously, by about an order of magnitude or more, at higher energies. We propose that these spectra result from photoions accelerated on the lunar dayside by nonmonotonic potentials (i.e.,potentials that do not decay to zero monotonically) and present a model for the expected differential flux. The energy of the cutoff and the magnitude of the differential flux are related to the properties of the local space environment and are consistent with the observed flux spectra. If this interpretation is correct, these surface‐based ion observations provide a unique perspective that both complements and enhances the conclusions obtained by remote‐sensing orbiter observations on the Moon's exospheric and electrostatic properties.

Stair-step↗