Search NASA⌕ Search

SEARCH · Search NASA

Results for “PLASMA FLUX MEASUREMENT”

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 541 records · Page 30
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

ISEE 1 observations of thermal plasma in the vicinity of the plasmasphere during periods of quieting magnetic activity

An investigation of thermal plasma behavior in the vicinity of the plasmasphere during periods of quieting magnetic activity was conducted by combining thermal ion observations made with the plasma composition experiment on ISEE 1 with plasma density profiles obtained from plasma frequency measurements made with the same satellite's plasma wave experiment. During periods in which the magnetic activity quiets, the two regions characterized by H(+):He(+):O(+) (isotropic) and H(+):O(+):He(+) (field-aligned) ion species distributions (in order of dominance) are separated by a new region in which low-energy H(+) and He(+) are found flowing along the magnetic field lines. At other times, following quieting magnetic activity, distributions having peak fluxes at 90 deg pitch angle are observed in this region.

Horwitz, J. L.↗
NASA NTRS2003

The Plasmoid Thruster Experiment (PTX)

A plasmoid is a compact plasma structure with an integral magnetic field. They have been studied extensively in controlled fusion research and are categorized according to the relative strength of the poloidal and toroidal magnetic field (B(phi), and B(tau), respectively). An object with B(phi)/B(tau) >> 1 is classified as a Field Reverse Configuration (FRC); if B(phi) = B(tau), it is called a Spheromak. There are a number of possible advantages to using accelerated plasmoids for in-space propulsion. A thruster based on this concept would operate by repetitively producing plasmoids and ejecting them from the device at high velocity. The plasmoid is formed inside of a single turn conical theta-pinch coil; as this process is inductive, there are no life-limiting electrodes. Similar experiments have yielded plasmoid velocities of at least 50 km/s (l), and calculations indicate that velocities in excess of 100 km/s are possible. A thruster based on this concept would be capable of producing an I(sp) in the range of 5,000 - 10,OOO s, with thrust densities of order 10(exp 5) N/m(exp 2). The current experiment is designed to produce jet powers in the range of 5-10 kW, although the concept should be scalable to higher power. The purpose of this experiment is to determine the feasibility of this plasma propulsion concept. To accomplish this, it will be necessary to determine: a.) specific impulse and thrust, b.) efficiency and mass utilization, c.) which type of plasmoid (FRC-like or Spheromak-like) gives the best performance, and d.) the characteristics required of actual thruster components (i.e., switch and capacitor technology). The plasmoid mass and velocity will be measured with a variety of diagnostics, including internal and external B-dot probes, flux loops, Langmuir probes, high-speed cameras, and an interferometer. Simulations of the plasmoid thruster using MOQUI, a time dependent MHD code, will be carried out concurrently with experimental testing. The PTX device is currently undergoing initial testing and preliminary experimental results are presented.

Eskridge, Richard↗
NASA NTRS2010

NASA's STEREO Mission

NASA's Solar-TErrestrial Relations Observatory mission, launched in 2006 October, consists of two nearly identical spacecraft in heliocentric orbits and currently 1380 of heliolongitude apart. Instrumentation on both spacecraft monitor solar wind plasma and magnetic field parameters, energetic particles, radio flux, and provide EUV and visible-light imaging of the corona, as well as novel, visible-light images of the ecliptic heliosphere. In addition to higher-resolution telemetry that enables a broad range of research into the propagation of disturbances in the inner heliosphere, a low-bandwidth, space weather beacon telemetry stream provides near-realtime information on each of these measurement types.

Gurman, Joseph B.↗
NASA NTRS1985

The cleft ion fountain - A two-dimensional kinetic model

The transport of ionospheric ions from a source in the polar cleft ionosphere through the polar magnetosphere is investigated using a two-dimensional, kinetic, trajectory-based code. The transport model includes the effects of gravitation, longitudinal magnetic gradient force, convection electric fields, and parallel electric fields. Individual ion trajectories as well as distribution functions and resulting bulk parameters of density, parallel average energy, and parallel flux for a presumed cleft ionosphere source distribution are presented for various conditions to illustrate parametrically the dependences on source energies, convection electric field strengths, ion masses, and parallel electric field strengths. The essential features of the model are consistent with the concept of a cleft-based ion fountain supplying ionospheric ions to the polar magnetosphere, and the resulting plasma distributions and parameters are in general agreement with recent low-energy ion measurements from the DE 1 satellite.

Horwitz, J. L.↗
NASA NTRS1995

Observations of Ionospheric Escape on Venus' Nightside

A population of low-energy (0-250 V E/q) ions with tailward directed velocity vectors and energies above that for escape from Venus is evident in nightside data from the Ames plasma analyzer on the Pioneer Venus Orbiter spacecraft. Good correlations with solar wind parameters were not obtained for the magnitudes of these ion fluxes, but tendencies for occurrence at times of tailward oriented magnetic fields and for alignment of the ion flows with the magnetic field were found. These tendencies seemed to be enhanced for higher-energy ions. In a few cases where comparisons were made, the ion fluxes were consistent with simultaneous O(+) measurements by the neutral mass spectrometer experiment on the spacecraft. The mean flux observed of the escaping nightside ions, averaged over an approximately 10-week-long spacecraft nightside season, was less than 2 x 10(exp 6)/sq cm/s.

Mihalov, J. D.↗
NASA NTRS1995

Observations of Ionospheric Escape on Venus' Nightside

A population of low-energy (0-250 V E/q) ions with tailward directed velocity vectors and energies above that for escape from Venus is evident in nightside data from the Ames plasma analyzer on the Pioneer Venus Orbiter spacecraft. Good correlations with solar wind parameters were not obtained for the magnitudes of these ion fluxes, but tendencies for occurrence at times of tailward oriented magnetic fields and for alignment of the ion flows with the magnetic field were found. These tendencies seemed to be enhanced for higher-energy ions. In a few cases where comparisons were made, the ion fluxes were consistent with simultaneous O(+) measurements by the neutral mass spectrometer experiment on the spacecraft. The mean flux observed of the escaping nightside ions, averaged over an approximately 10-week-long spacecraft nightside season, was less than 2 x 10(exp 6) cm(exp -2) s(exp -1).

Mihalov, J. D.↗
NASA NTRS1987

A comparison of the Mercury and earth magnetospheres - Electron measurements and substorm time scales

The present search for similarities between earth and Mercury plasma electron distribution and large-scale dynamics notes that both spectral shapes are similar to a kappa-distribution. A model distribution of this type which incorporates convective flow is used to simulate the observed plasma electron spectral variations near the Mariner 10-Mercury 1 A event; convection appears to be stronger before, rather than during, the A event, in contradiction to the Baker (1986) convective injection model for Mercury's two relativistic electron flux enhancements. Mercury's postmidnight energetic electron B and B-prime events seem to be multiple onsets in the course of a substorm.

Christon, S. P.↗
NASA NTRS1991

Comparison of Doppler scintillation and in situ spacecraft plasma measurements of interplanetary disturbances

Results are presented of detailed comparisons between Doppler scintillation and in situ plasma measurements to improve the understanding of Doppler scintillation transients. During a combined observing period of nearly 3 mo in 1981-1982 near solar maximum, 22 transients were observed by the Pioneer Venus Orbiter spacecraft and 23 shocks were observed by Helios 1. It is found that at least 84 percent of the transients are shocks, while at least 90 percent of the shocks are transients. Although the temporal profiles of Doppler scintillation and mass flux density are similar, the magnitudes of the Doppler scintillation transients may not simply reflect those of mass flux density. Only one pronounced solar wind event that was observed in the mass flux density measurements showed no signature in the scintillation data; field and particle measurements by Helios 1 suggest that it is a noncompressive density enhancement and/or a magnetic cloud. It is shown that Doppler scintillation measurements can now be used by themselves to detect and locate interplanetary shocks near the sun with a relatively high degree of certainty.

Woo, Richard↗
NASA NTRS1996

Latitudinal Dependence of the Radial IMF Component - Interplanetary Imprint

Ulysses measurements have confirmed that there is no significant gradient with respect to heliomagnetic latitude in the radial component, B(sub r,), of the interplanetary magnetic field. There are two processes responsible for this observation. In the corona, the plasma beta is much less than 1, except directly above streamers, so both longitudinal and latitudinal (meridional) gradients in field strength will relax, due to the transverse magnetic pressure gradient force, as the solar wind carries magnetic flux away from the Sun. This happens so quickly that the field is essentially uniform by 5 solar radius. Beyond 10 solar radius, beta is greater than 1 and it is possible for a meridional thermal pressure gradient to redistribute magnetic flux - an effect apparently absent in Ulysses and earlier ICE and Interplanetary Magnetic Physics (IMP) data. We discuss this second effect here, showing that its absence is mainly due to the perpendicular part of the anisotropic thermal pressure gradient in the interplanetary medium being too small to drive significant meridional transport between the Sun and approx. 4 AU. This is done using a linear analytic estimate of meridional transport. The first effect was discussed in an earlier paper.

Suess, S. T.↗
NASA NTRS2019

Reconstruction of Schiaparelli and Comars Flight Data

ESA recently flew an entry, descent, and landing demonstrator module called Schiaparelli that entered the atmosphere of Mars on the 19th of October, 2016. The instrumentation suite included heatshield and backshell pressure transducers and thermocouples (known as AMELIA) and backshell radiation and direct heatflux-sensing sensors (known as COMARS and ICOTOM). Due to the failed landing of Schiaparelli, only a subset of the flight data was transmitted before and after plasma black-out. The goal of this paper is to present comparisons of the flight data with calculations from NASA simulation tools, DPLR/NEQAIR and LAURA/HARA. DPLR and LAURA are used to calculate the flowfield around the vehicle and surface properties, such as pressure and convective heating. The flowfield data are passed to NEQAIR and HARA to calculate the radiative heat flux. Comparisons will be made to the COMARS total heat flux, radiative heat flux and pressure measurements. Results will also be shown against the reconstructed heat flux which was calculated from an inverse analysis of the AMELIA thermocouple data performed by Astrium. Preliminary calculations are presented in this abstract. The aerodynamics of the vehicle and certain as yet unexplained features of the inverse analysis and forebody data will be investigated.

Schiaparelli↗
NASA NTRS1987

Plasma observations at the earth's magnetic equator

New observations of particle and wave data from the magnetic equator from the DE 1 spacecraft are reported. The results demonstrate that the equatorial plasma population is predominantly hydrogen and that the enhanced ion fluxes observed at the equator occur without an increase in the total plasma density. Helium is occasionally found heated along with the protons, and forms about 10 percent of the equatorially trapped population at such times. The heated H(+) ions can be characterized by a bi-Maxwellian with kT(parallel) = 0.5-1.0 eV and kT = 5-50 eV, with a density of 10-100/cu cm. The total plasma density is relatively constant with latitude. First measurements of the equatorially trapped plasma and coincident UHR measurements show that the trapped plasma is found in conjunction with equatorial noise.

Olsen, R. C.↗
NASA NTRS2017

Applications of Radiative Heating for Space Exploration

Vehicles entering planetary atmospheres at high speeds (6 - 12 kms) experience intense heating by flows with temperatures of the order 10 000K. The flow around the vehicle experiences significant dissociation and ionization and is characterized by thermal and chemical non-equilibrium near the shock front, relaxing toward equilibrium. Emission from the plasma is intense enough to impart a significant heat flux on the entering spacecraft, making it necessary to predict the magnitude of radiative heating. Shock tubes represent a unique method capable of characterizing these processes in a flight-similar environment. The Electric Arc Shock tube (EAST) facility is one of the only facilities in its class, able to produce hypersonic flows at speeds up to Mach 50. This talk will review the characterization of radiation measured in EAST with simulations by the codes DPLR and NEQAIR, and in particular, focus on the impact these analyses have on recent missions to explore the solar system.

simulations↗
NASA NTRSDate not supplied

Development of a Composite Material Aerodynamic Demise Model for the Object Reentry Survival Analysis Tool (ORSAT)

The reentry demise of fiber-reinforced polymer (FRP) composites is an increasing concern for modern spacecraft at end of life. Unlike traditional materials such as metals, shredding of the material by aerodynamic forces appears to be a major component of the reentry demise mechanism. This paper will describe a new mechanical, strength-based, material demise model for the Object Reentry Survival Analysis Tool (ORSAT) Version 7.1. The model is based on laboratory in-situ and residual strength tests of several FRP materials performed during the NASA Orbital Debris Program Office’s Phase II Composite Material Demise test campaign. To test the residual strength of partially charred FRP materials, the authors tested 107 rectangular shaped samples of different thicknesses that were previously exposed to high-enthalpy flow at the University of Texas at Austin’s Inductively Coupled Plasma Torch facility. Tests were performed under normal atmospheric conditions at NASA Johnson Space Center’s Experimental Impact Laboratory using a Chatillon TCD1000 tensile test machine configured with a three-point bending jig. Mean fracture load, residual strength, delamination, and flexural modulus were measured for each test. An engineering model of aeromechanical demise for each material was developed by correlating the measured residual strength of the samples with the duration and magnitude of the applied heat flux and the mass loss and char progression. This model has been implemented in ORSAT 7.1 for the built-in, charring carbon fiber/epoxy and charring glass fiber/epoxy material models. The new model was verified by calculating the demise of hundreds of FRP composite fragments of various shapes and sizes and checking the calculations for consistency, with specific focus on material characterization in one-dimension. Further tests are planned in hypersonic flow facilities to validate the assumptions used in the model.

Priscilla A. Mendoza↗
NASA NTRSDate not supplied

Development of a Composite Material Aerodynamic Demise Model for the Object Reentry Survival Analysis Tool (ORSAT)

The reentry demise of fiber-reinforced polymer (FRP) composites is an increasing concern for modern spacecraft at end of life. Unlike traditional materials such as metals, shredding of the material by aerodynamic forces appears to be a major component of the reentry demise mechanism. This paper will describe a new mechanical, strength-based, material demise model for the Object Reentry Survival Analysis Tool (ORSAT) Version 7.1. The model is based on laboratory in-situ and residual strength tests of several FRP materials performed during the NASA Orbital Debris Program Office’s Phase II Composite Material Demise test campaign. To test the residual strength of partially charred FRP materials, the authors tested 107 rectangular shaped samples of different thicknesses that were previously exposed to high-enthalpy flow at the University of Texas at Austin’s Inductively Coupled Plasma Torch facility. Tests were performed under normal atmospheric conditions at NASA Johnson Space Center’s Experimental Impact Laboratory using a Chatillon TCD1000 tensile test machine configured with a three-point bending jig. Mean fracture load, residual strength, delamination, and flexural modulus were measured for each test. An engineering model of aeromechanical demise for each material was developed by correlating the measured residual strength of the samples with the duration and magnitude of the applied heat flux and the mass loss and char progression. This model has been implemented in ORSAT 7.1 for the built-in, charring carbon fiber/epoxy and charring glass fiber/epoxy material models. The new model was verified by calculating the demise of hundreds of FRP composite fragments of various shapes and sizes and checking the calculations for consistency, with specific focus on material characterization in one-dimension. Further tests are planned in hypersonic flow facilities to validate the assumptions used in the model.

Priscilla A. Mendoza↗
NASA NTRS1991

Picked-up protons near Mars - Phobos observations

The measurements carried out by the plasma spectrometer, Aspera, on board the Phobos-2 spacecraft show that protons, originating in the extended hydrogen corona of Mars, were observed at altitudes not greater than 7500 km. The cyclotron instability of these pickup ions appears to generate Alfven waves observed by the Magma magnetometer. Analysis of the plasma data shows that weak pitch-angle diffusion of a ring-distribution of pickup protons occurs. The altitude profiles of pickup proton fluxes and number densities of the parent hydrogen atoms are derived.

Barabash, S.↗
NASA NTRS1994

High-velocity plasma in the transition region of AU Microscopii: Evidence for magnetic reconnection and saturated heating during quiescent and flaring conditions

We analyze high-resolution HST spectra of the dMOe flare star AU Mic, including the profiles of the C IV 1548.2 A, 1550.8 A and Si IV 1393.8 A, 1402.8 A lines obtained with the G160M grating of the Goddard High-Resolution Spectrograph. The quiescent profiles of the C IV and Si IV lines are broad, and not simple Gaussians in shape. Flux in the C IV and Si IV lines, for example, can be measured reliably out to about +/- 200 km/s from line center. Each of the C IV and Si IV profiles can be fitted accurately by two Gaussians (one narrow and the other broad) centered on nearly the same wavelength, with the narrower component accounting for roughly 60% ofthe total integrated flux. The narrow components have similar line widths to those observed in solar active and quiet regions. The broad Gaussian components of the AU Mic line profiles are reminiscent of the broad C IV profiles observed in solar transition region explosive events, which are thought to be associated with emerging magnetic flux regions where field reconnection occurs.

Linsky, Jeffrey L.↗
NASA NTRS2018

Kinetic Properties of an Interplanetary Shock Propagating Inside a Coronal Mass Ejection

We investigate the kinetic properties of a typical fast-mode shock inside an interplanetary coronal mass ejection (ICME) observed on 1998 August 6 at 1 au, including particle distributions and wave analysis with the in situ measurements from Wind. Key results are obtained concerning the shock and the shock-ICME interaction at kinetic scales: (1) gyrating ions, which may provide energy dissipation at the shock in addition to wave-particle interactions, are observed around the shock ramp; (2) despite the enhanced proton temperature anisotropy of the shocked plasma, the low plasma beta inside the ICME constrains the shocked plasma under the thresholds of the ion cyclotron and mirror-mode instabilities; (3) whistler heat flux instabilities, which can pitch-angle scatter halo electrons through a cyclotron resonance, are observed around the shock, and can explain the disappearance of bi-directional electrons (BDEs) inside the ICME together with normal betatron acceleration; (4) whistler waves near the shock are likely associated with the whistler heat flux instabilities excited at the shock ramp, which is consistent with the result that the waves may originate from the shock ramp; (5) the whistlers share a similar characteristic with the shocklet whistlers observed by Wilson et al., providing possible evidence that the shock is decaying because of the strong magnetic field inside the ICME.

Liu, Mingzhe↗
NASA NTRS2002

X-ray Observations of the Supernova Remnants G349.7+0.2 and CTA 1

This compact, high luminosity SNR is known to be interacting with a molecular cloud, based on the observation of OH masers. The maser lines provide velocity measurements which place the remnant at a distance of 22 kpc. The analysis of our ASCA data is now complete. We find that the X-ray emission from this remnant is dominated by material of solar abundances, consistent with the picture of a molecular cloud interaction. At the very large distance indicated by the masers, the observed flux makes G349.7+0.2 one of the most luminous SNRs in our galaxy. We show that the X-ray emitting plasma is not in ionization equilibrium, and that while the remnant has swept up large amounts of material, it is actually relatively young, holding some promise for identification of stellar ejecta in future high resolution studies. A paper detailing our analysis and results has been completed and is in the final stages of circulation amongst co-authors prior to submission to ApJ.

Slane, Patrick O.↗