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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

Effects of large zonal plasma drifts on the subauroral ionosphere

A model of the earth's ionosphere and plasmasphere is used to investigate the effects of an imposed westward plasma drift of maximum velocity 2 km/s. A closed subauroral tube of plasma is considered and the velocity spike persists for 10 min. Ion-neutral frictional heating causes rapid elevation of the F-region O(+) temperature. The F-layer O(+) concentration is decreased due to increased O(+) loss rate and rapid ion flows both upward and downward from the F-region. The upward flux of O(+) through the topside ionosphere can each 5 x 10 exp 9/sq cm/s; when the velocity spike ceases there is a return flow of O(+) that tends to replenish the F-layer. Most of the features revealed by the model for the F-region and topside ionosphere are in accord with observations of subauroral ion drifts. Downward flows that are predicted to be persistently present around the 300 km altitude level appear to agree with observations only occasionally; suggestions are made to resolve this discrepancy.

Sellek, R.↗
NASA NTRS1993

Particle drift in the Earth's plasma sheet

We generalize the derivation of the average gradient/curvature-drift for a flux tube filled with an isotropic distribution of particles at specified kinetic energy. The present treatment is restricted to a two-dimensional magnetic field with zero electric field, but it includes all chaotic and Speiser orbits, which do not correspond to the simple picture of gradient/curvature drift. We assume that particles are evenly distributed throughout the regions of phase space allowed by their energy and canonical momentum. This assumption is closely related but not exactly equivalent to the assumption of isotropic pitch-angle distribution. Our derivation assumes that the maximum Larmor radius is small compared to the scale length for equatorial variations in the flux tube volume, but it does not involve any restrictions on the curvature of the field line. The resulting expression for the drift rate is valid for situations where the particle drift velocity is comparable to the thermal speed in some regions. The apparent implication of this generalized treatment is that the existence of very complex non-adiabatic particle trajectories in the plasma sheet may not invalidate previous estimates of the average rate of particle drift out the sides of the tail, estimates that were made under the assumption of simple guiding-center drifts.

Wolf, R. A.↗
NASA NTRS1981

Development report: Automatic System Test and Calibration (ASTAC) equipment

A microcomputer based automatic test system was developed for the daily performance monitoring of wind energy system time domain (WEST) analyzer. The test system consists of a microprocessor based controller and hybrid interface unit which are used for inputing prescribed test signals into all WEST subsystems and for monitoring WEST responses to these signals. Performance is compared to theoretically correct performance levels calculated off line on a large general purpose digital computer. Results are displayed on a cathode ray tube or are available from a line printer. Excessive drift and/or lack of repeatability of the high speed analog sections within WEST is easily detected and the malfunctioning hardware identified using this system.

Thoren, R. J.↗
NASA NTRS1988

Studies of ionospheric plasma and electrodynamics and their application to ionosphere-magnetosphere coupling

The contribution of the Dynamics Explorer (DE) program to the study of small-scale structure in the equatorial ionospheric number density and the bulk motion of the plasma in the equatorial ionosphere is considered. DE results have helped elucidate the role of E region and F region winds in decreasing the magnitude of variations in the east-west plasma drift at night, as a function of magnetic flux tube apex height, with increasing height above the altitude of the peak F region concentration. Other results concern the ionospheric convection pattern at high latitudes during periods of southward IMF, the magnetosphere/solar-wind interaction that may be involved in the production of the convection pattern, and the characteristics of the high-latitude ionospheric plasma motion during periods of northward IMF.

Heelis, R. A.↗
NASA NTRS1971

Thin electrostatically self-focusing electron streams.

Study of 30 to 380 microampere, 50 to 550 V, 1 to 2 mm, electrostatically self-focusing electron streams (50 cm long) drifting through mercury vapor (at 50 microtorr to 2 millitorr) in a tube with a radius of 6.6 cm. The inside surface of the tube is coated with a transparent layer whose resistivity is 50 ohm-cm per centimeter. In order to determine the charged-particle densities and the potential profile in and around the beam without disturbing the system, a multigrid electrostatic charged particle energy analyzer was used to study separately the energy distributions of both ions and electrons ejected radially from the beam. The results show two energy groupings for electrons. The energy distribution of the high-energy group is produced by ionizing collisions between beam electrons and neutral gas atoms; a group of flow-energy electrons becomes trapped in the potential well within and around the beam, subsequently escaping by collisional mechanisms.

Mccorkle, R. A.↗
NASA NTRS1984

The measured motions inside equatorial plasma bubbles

A preliminary study of the vertical and north-south horizontal ion motions in plasma bubbles in the near-equatorial ionosphere utilizing drift meter data from Atmosphere Explorer E is presented. High-resolution data show that the vertical ion velocity in some bubbles increases approximately linearly with (N(0)-N)/N, where N(0) is the background ion concentration and N is the bubble ion concentration. At sufficiently large N(0)/N the vertical ion velocity saturates, but often at a value substantially larger than the ratio of the gravitational acceleration to the ion neutral collision frequency. These larger than nominal velocities may result from background eastward electric fields and/or from a vertically elongated bubble cross section. The unanticipated observation that large poleward horizontal drifts accompany these vertical drifts seems to follow naturally from a redistribution of plasma along flux tubes as the plasma convects from the bottomside of the F region to high altitudes.

Hanson, W. B.↗
NASA NTRS1986

The measured motions inside equatorial plasma bubbles

A preliminary study of the vertical and north-south horizontal ion motions in plasma bubbles in the near-equatorial ionosphere utilizing drift meter data from Atmosphere Explorer E is presented. High resolution data show that the vertical ion velocity in some bubbles increase approximately linearly with (N(0)-N)N, where N(0) is the background ion concentration and N is the bubble ion concentration. At sufficiently large N(0)/N the vertical ion velocity saturates, but often at a value substantially larger than the ratio of the gravitational acceleration to the ion neutral collision frequency. These larger than nominal velocities may result from background eastward electric fields and/or from a vertically elongated bubble cross section. The unanticipated observations that large poleward horizontal drifts accompany these vertical drifts seems to follow naturally from a redistribution of plasma along flux tubes as the plasma convects from the bottomside of the F region to high altitudes.

Hanson, W. B.↗
NASA NTRS2013

Micro-XRF for In Situ Geological Exploration of Other Planets

In situ analysis of rock chemistry is a fundamental tool for exploration of planets. To meet this need, a high-spatial-resolution micro x-ray fluorescence (Micro-XRF) instrument was developed that is capable of determining the elemental composition of rocks (elements Na U) with 100 microns spatial resolution, thus providing insight to the composition of features as small as sand grains and individual laminae. The resulting excitation beam is of sufficient intensity that high signal-to-noise punctual spectra are acquired in seconds to a few minutes using an Amptek Silicon Drift Detector (SDD). The instrument features a tightly focused x-ray tube and HVPS developed by Moxtek that provides up to 200 micro-A at 10 to 50 keV, with a custom polycapillary optic developed by XOS Inc. and integrated into a breadboard Micro-XRF (see figure). The total mass of the complete breadboard instrument is 2.76 kg, including mounting hardware, mounting plate, camera, laser, etc. A flight version of this instrument would require less than 5W nominal power and 1.5 kg mass. The instrument includes an Amptek SDD that draws 2.5 W and has a resolution of 135 to 155 eV FWHM at 5.9 keV. It weighs 180 g, including the preamplifier, digital pulse processor, multichannel analyzer, detector and preamp power supplies, and packaging. Rock samples are positioned relative to the instrument by a three-axis arm whose position is controlled by closed-loop translators (mimicking the robotic arm of a rover). The distance from the source to the detector is calculated from the position of a focused laser beam on the sample as imaged by the camera. The instrument enables quick scans of major elements in only 1 second, and rapid acquisition (30 s) of data with excellent signal-to-noise and energy resolution for trace element analysis

Wade, Lawrence A.↗
NASA NTRS1986

Support of the balloon-borne ultraviolet stellar spectrograph

A (256 x 1024)-pixel imaging ultraviolet Multi-mode Microchannel Array (MAMA) detector system for flight was fabricated, evaluated, and environmentally tested for flight on the Balloon Borne Ultraviolet Stellar Spectrograph (BUSS). The goal of the program was to replace the existing SEC Vidicon with the pulse-counting MAMA detector in order to, first, improve the overall sensitivity of the BUSS telescope and spectrograph for observations of stars down to m sub v = 7 and fainter, and, second, to improve the spectral resolution and wavelength accuracy by eliminating the image drifts in the Vidicon caused by magnetic field effects. A sealed MAMA detector tube structure employing a remotely processed photocathode mounted on a window in proximity focus with the front face of the MCP was developed to avoid contamination produced by a noisy and unstable device. The configuration of the BUSS detector system in its flight ready configuration is shown. The quantum efficiency curve for the semi-transparent Cs2Te photocathode is also shown.

Timothy, J. G.↗
NASA NTRS2012

Electrospray Collection of Lunar Dust

A report describes ElectroSpray Ionization based Electrostatic Precipitation (ESIEP) for collecting lunar dust particles. While some HEPA filtration processes may remove a higher fraction (>99.9 percent) of the particles, the high efficiency may not be appropriate from an overall system standpoint, especially in light of the relatively large power requirement that such systems demand. The new electrospray particle capture technology is described as a variant of electrostatic precipitation that eliminates the current drawbacks of electrostatic precipitation. The new approach replaces corona prone field with a mist of highly charged micro-droplets generated by electrospray ionization (ESI) as the mechanism by which incoming particles are attracted and captured. In electrospray, a miniscule flow rate (microliters/minute) of liquid (typically water and a small amount of salt to enhance conductivity) is fed from the tip of a needle held at a high voltage potential relative to an opposite counter electrode. At sufficient field strength, a sharp liquid meniscus forms , which emits a jet of highly charged droplets that drift through the surrounding gas and are collected on the walls of a conductive tube. Particles in the gas have a high probability of contact with the droplets either by adhering to the droplets or otherwise acquiring a high level of charge, causing them to be captured on the collecting electrode as well. The spray acts as a filtration material that is continuously introduced and removed from the gas flow, and thus can never become clogged.

Dziekan, Michael↗
NASA NTRS2000

Trapped Energetic Electrons in the Magnetosphere of Ganymede

On May 7, 1997, the Galileo orbiter flew through the magnetosphere of Ganymede and crossed flux tubes connected at both ends to the satellite. Energetic electrons, observed during this encounter by means of the Energetic Particle Detector on board Galileo, showed double loss cones and "butterfly" type pitch angle distributions, as has been noted in past publications. In addition, as the spacecraft flew toward Ganymede, both the shape and magnitude of the spectrum changed. The intensities decreased, with the greatest depletion observed at the lowest energies, and the monotonic slope characteristic of the Jovian environment was replaced by a rollover of the spectrum at the low-energy end. The spectra lead us to infer a strongly energy-dependent injection efficiency into the trapping region. As on previous encounters, the pitch angle distributions confirmed the position of the magnetopause as indicated by the magnetometer measurements, but the spectra remained Jovian until the trapping region was reached. Various physical mechanisms capable of generating the observed spectra and pitch angle distributions, including downstream reconnection insertion followed by magnetic gradient drift and absorption of the lowest-energy electrons by Ganymede and injection from Jovian flux tubes upstream are assessed.

Eviatar, Aharon↗
NASA NTRS1979

Simultaneous multifrequency observations of Jovian S bursts

The millisecond component of the Jovian decameter emission was studied at high resolution in order to examine the short-term behavior of the S-burst drift rates and to define the drift rate spectrum at high frequencies. By using dynamic spectra of 300 microsec and 3.3 kHz resolution and covering discrete frequency bands in the 26-33 MHz range, large systematic changes in the magnitude of the S-burst drift rates are observed on a time scale of seconds to minutes. The drift rate variability, its dependence on frequency, and absence of the predicted drift rate turnover in the spectrum are interpreted in terms of an ionospheric electron source. Low-resolution intensity-time tracings, abrupt changes in mean drift rates from group to group, and systematic variations in the group-to-group mean drift rates due to predictable temporal changes in the magnetic field gradient on the Io flux tube are discussed. These temporal changes are due to motion of the Io-associated magnetic flux tube in the Jovian magnetosphere.

Flagg, R. S.↗
NASA NTRS1986

Theoretical comments on the nature of the plasmapause

The traditional theoretical interpretations of the observed plasmapause are compared, namely, the plasmapause as: (1) The boundary between closed flux tubes that have been in the inner magnetosphere for several days and those that have recently drifted in from the magnetotail or (2) the last closed electric equipotential. Although the two interpretations become equivalent in the case where the electric-field pattern is steady for several days, interpretation 1 seems theoretically more secure for typical magnetospheric conditions, due to the essentially time-dependent nature of the magnetospheric electric field. The results of old theoretical studies of the effects of time variations in the electric-field pattern on the shape of the plasmapause are reviewed briefly. The formulation of the present version of the Rice Convection Model is also reviewed. Preliminary results of recent computations of quiet-time electric fields, carried out with this model, are presented and discussed. Quiet-time thermospheric winds are found to have only minor effects on drift paths of magnetospheric particles.

Wolf, R. A.↗
NASA NTRS1992

Ring current instabilities in the magnetohydrodynamic frequency range

This report summarizes recent theoretical developments in ring current plasma instabilities in the magnetohydrodynamic (MHD) frequency range but with the effect of finite Larmor radius, and discusses its relevance to satellite-based observations. Possible instabilities are the bounce resonant instabilities caused by a humped energy distribution, the drift mirror instability caused by an anisotropic pressure and the drift wave type instability caused by a combination of drift-bounce resonance and reduced Alfven frequency due to a high beta loading of the flux tube. Here, beta is proportional to plasma/magnetic pressures. Mechanisms leading to turbulence are also discussed.

Hasegawa, A.↗
NASA NTRS1996

Global, Collisional Model of High-Energy Photoelectrons

A previously-developed colissional, interhemispheric flux tube model for photoelectrons (PE) has been extended to three dimensions by including transport due to vector E x vector B and magnetic gradient-curvature drifts. Using this model, initial calculations of the high-energy (greater then 50 eV) PE distribution as a function of time, energy, pitch angle, and spatial location in the equatorial plane, are reported for conditions of low geomagnetic activity. To explore both the dynamic and steady behaviors of the model, the simulation starts with the abrupt onset of photoelectron excitation, and is followed to steady state conditions. The results illustrate several features of the interaction of photoelectrons with typical magnetospheric plasmas and fields, including collisional diffusion of photoelectrons in pitch angle with flux tube filling, diurnal intensity and pitch angle asymmetries introduced by directional sunlight, and energization of the photoelectron distribution in the evening sector. Cross-field drift is shown to have a long time scale, taking 12 to 24 hours to reach a steady state distribution. Future applications of the model are briefly outlined.

Khazanov, G. V.↗
NASA NTRSDate not supplied

Bessel Tube to Capture Lunar Volatiles

Current arts to create linear motion or acceleration of fine particles and molecules into devices such as mass spectrometers and vacuum pumps rely on the pressure difference created by a pinhole or mechanical processes. However, in an environment of vacuum, these approaches do not create such a pressure differential to drive and move fine particles and molecules. In some cases, electrostatic or magnetic processes may work to create the desired motion. A cylindrical harmonic of electric field, which is widely used in electron accelerators, offers a unique capability to capture and induce a linear motion of molecules and particles when electrically charged. Generally, lunar volatiles are electrostatically charged. The idea to capture and collect the lunar volatiles by creating a drift axis of motion using a cylindrical harmonic field has led to the development of a device concept, called a Bessel Tube. The Bessel Tube concept ingests fine particles, gaseous atoms, and gaseous molecules and guides them along an extraction tube for collection, separation, and analysis. The Bessel Tube concept for lunar volatile collection is discussed.

Bessel Tube↗
NASA NTRS1976

A model study of diurnal behavior of the ionosphere and the protonosphere coupling

A new method to study dynamic behavior of the ionosphere-protonosphere coupling within the plasmasphere is developed and used to calculate ion distributions above 500 km using observed electron densities at 500 km. The method is based on the relation between the total magnetic flux tube content of H(+) above some reference height (e.g., 3000 km) and the H(+) flux at that height, which is uniquely determined by the coupled momentum and continuity equations for the quasi-steady state. The O(+) profile is perturbed from diffusive equilibrium only by ion drag with H(+). The time dependency is taken into account by applying self-consistent boundary conditions which are obtained from the solution of the time-dependent equation for the tube content of H(+). Calculations are carried out for two models. The first model deals with the ion dynamics in a tube of force which rotates with the earth. In the second model, effects of the cross-L plasma drifts are considered. Both models produce diurnal variations of H(+) and O(+) densities near 1000 km similar to observational results.

Marubashi, K.↗
NASA NTRS1992

The temporal evolution of the ionospheric signatures of subauroral ion drifts

The effects of an imposed westward plasma drift on O(+) and molecular ion behavior in the nightside ionosphere are investigated using a model of the ionosphere and plasmasphere. A closed subauroral tube of the plasma is considered, and the velocity input persists for 30 min. The rapid increase in the F-region ion temperature resulting from ion-neutral frictional heating causes an immediate surge in the O(+) field-aligned velocity, upwards in the topside ionosphere and downwards below the F2-peak, but after about 10 min into the event the surge in the topside disappears. After the event there is a return flow of O(+) from the plasmasphere. The relative abundance of O(+) decreases during the event due to the increased rate of conversion of O(+) into NO(+) and O2(+); the decrease is more marked for greater values of the imposed westward ion drift. The implications of these results for satellite observations of subauroral ion drifts events and on EISCAT incoherent scatter radar observations of ion heating events is discussed.

Moffett, R. J.↗