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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 487 records · Page 27
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Response of Venus exospheric temperature measured by neutral mass spectrometer to solar EUV flux measured by Langmuir probe on the Pioneer Venus orbiter

The photoelectron current from the Pioneer Venus Langmuir probe has provided measurements of the total flux of solar EUV photons at Venus since 1979. The neutral oxygen scale height measured by the orbiter neutral mass spectrometer has permitted the exospheric temperature to be derived during the same mission. In this paper, the EUV observations are used to examine the response of exospheric temperature to changes in solar activity, primarily those related to solar rotation. It is found that the dayside exospheric temperature quite faithfully tracks variations in the EUV flux. Comparison is also made with the earth-based solar activity index F10.7 adjusted to the position of Venus. This index varied from 142 to 249 flux units during the period of measurements. The exospheric temperature is better correlated with EUV flux than with the 10.7-cm solar radio flux.

Mahajan, K. K.↗
NASA NTRS1975

Solar gamma-ray lines as probes of accelerated particle directionalities in flares

Anisotropies of charged particles accelerated in solar flares were studied by observing Doppler shifts of selected gamma-ray lines. The spectral shape was calculated of the 6.1-MeV line of O-16. If the accelerated particles are isotropic, the line remains centered at e sub 0 = 6129.4 keV, and its width (FWHM) is about 100 keV. For particle anisotropies that may be produced in solar flares, the line is shifted to lower energies by about 30 to 40 keV.

Ramaty, R.↗
NASA NTRS1976

Solar gamma-ray lines as probes of accelerated particle directionalities in flares

Anisotropies of charged particles accelerated in solar flares can be studied by observing Doppler shifts of selected gamma-ray lines. The spectral shape of the 6.1-MeV line of O-16 is calculated. If the accelerated particles are isotropic, the line remains centered at an emitting-nucleus rest-frame energy of 6129.4 keV, and its width (FWHM) is about 100 keV. However, for particle anisotropies that may be produced in solar flares, the line is shifted to lower energies by about 30 to 40 keV.

Ramaty, R.↗
NASA NTRS1977

The comet-solar wind interaction

The important roles of comets as natural probes of the solar wind, particularly at high heliographic latitudes and small heliocentric distances, unattained thus far by artificial space probes, is stressed. It is becoming clear the solar wind is not merely responsible for shaping and maintaining the cometary plasma tail, but is also indirectly responsible for the rapid ionization processes in the coma. Despite this, however, the detailed interaction of the solar wind with comets, which is underlined by the complex and time-varying morphology observed in the cometary head and the tail, constitutes a formidable problem, and is only very imperfectly understood at present. The current views are critically reviewed and an attempt is made to identify the dominant physical mechanisms that are involved.

Mendis, D. A.↗
NASA NTRS1998

From the Sun to Pluto

From the Sun to Pluto, all by the way of Jupiter. The Outer Planets/Solar Probe (OP/SP) Project first three missions will all visit Jupiter before reaching their destinations of the Sun, the Jupiter moon Europa and the Pluto/Charon system.

OP/SP↗
NASA NTRS1999

The Magnetospheric Multiscale Mission...Resolving Fundamental Processes in Space Plasmas

The Magnetospheric Multiscale (MMS) mission is a multiple-spacecraft Solar-Terrestrial Probe designed to study the microphysics of magnetic reconnection, charged particle acceleration, and turbulence in key boundary regions of Earth's magnetosphere. These three processes, which control the flow of energy, mass, and momentum within and across plasma boundaries, occur throughout the universe and are fundamental to our understanding of astrophysical and solar system plasmas. Only in Earth's magnetosphere, however, are they readily accessible for sustained study through in-situ measurement. MMS will employ five co-orbiting spacecraft identically instrumented to measure electric and magnetic fields, plasmas, and energetic particles. The initial parameters of the individual spacecraft orbits will be designed so that the spacecraft formation will evolve into a three-dimensional configuration near apogee, allowing MMS to differentiate between spatial and temporal effects and to determine the three dimensional geometry of plasma, field, and current structures. In order to sample all of the magnetospheric boundary regions, MMS will employ a unique four-phase orbital strategy involving carefully sequenced changes in the local time and radial distance of apogee and, in the third phase, a change in orbit inclination from 10 degrees to 90 degrees. The nominal mission operational lifetime is two years. Launch is currently scheduled for 2006.

Curtis, S.↗
NASA NTRS2002

Laboratory Studies in UV and EUV Solar Physics

The Ion Beam Experiment at the Center for Astrophysics is dedicated to the study of ion-electron collision processes of importance in solar physics. The analysis of measurements of Electron Impact Excitation (EIE) from the 3s3p(exp 3)P(exp o) metastable state to the 3s3p(exp 1)P state of Si(2+) was completed during the past year and a paper describing the results is available as a preprint. Our current program is directed at measuring absolute cross sections for dielectronic recombination (DR) and EIE in Si(3+), one of the primary ions used for probing the solar transition region. Our study of DR is particularly concerned with the effects of electric and magnetic fields on the recombination rates. Measurements of silicon ions with charge greater than n=2 have necessitated upgrading the experiment with a new ion source. The new source is also suitable for producing C(2+) beams to be used for measurements of EIE and DR for that system. The source is expected to be capable of producing beams of more highly charged systems as well.

Parkinson, W. H.↗
NASA NTRS2012

Future Gamma-Ray Imaging of Solar Eruptive Events

Solar eruptive events, the combination of large solar flares and coronal mass ejections (CMEs), accelerate ions to tens of Gev and electrons to hundreds of MeV. The energy in accelerated particles can be a significant fraction (up to tens of percent) of the released energy and is roughly equipartitioned between ions and electrons. Observations of the gamma-ray signatures produced by these particles interacting with the ambient solar atmosphere probes the distribution and composition of the accelerated population, as well as the atmospheric parameters and abundances of the atmosphere, ultimately revealing information about the underlying physics. Gamma-ray imaging provided by RHESSI showed that the interacting approx.20 MeV/nucleon ions are confined to flare magnetic loops rather than precipitating from a large CME-associated shock. Furthermore, RHESSI images show a surprising, significant spatial separation between the locations where accelerated ions and electrons are interacting, thus indicating a difference in acceleration or transport processes for the two types of particles. Future gamma-ray imaging observations, with higher sensitivity and greater angular resolution, can investigate more deeply the nature of ion acceleration. The technologies being proven on the Gamma-Ray Imager/Polarimeter for Solar flares (GRIPS), a NASA balloon instrument, are possible approaches for future instrumentation. We discuss the GRIPS instrument and the future of studying this aspect of solar eruptive events.

Shih, Albert↗
NASA NTRS2003

Laboratory Studies in UV and EUV Solar Physics

The Ion Beam Experiment at the Center for Astrophysics is dedicated to the study of ion-electron collision processes of importance in solar physics. A paper describing our most recent measurement 'Absolute cross section for Si(2+)(3s3p(sup 3)Rho (sup 0) yields 3s3p(sup 1)Rho(sup 0)) electron-impact excitation' was published during the past year. Dr. Paul Janzen received his PhD. from the Harvard Physics Department on the basis of this and other work, such as the new electron cyclotron resonance (ECR) ion source. The ion source is producing stable beams with large currents for our present work on C(2+), and it also produces stable beams with large currents of more highly charged systems, for future work on systems such as O(4+). The past year has been focussed on our current program to measure absolute cross sections for Electron Impact Excitation (EIE) in C(2+), one of the primary ions used for probing the solar transition region. C(2+) beams produced by the ion source have been transported to the interaction region of the experiment, where the collisions are studied, and Visiting Scientist Dr. Adrian Daw is currently collecting data to measure the C(2+)(2s2p(sup 3)Rho(sup 0) yields 2p(sup 2)(sup 3)Rho) EIE cross section as a function of collision energy, under the guidance of Drs. John Kohl, Larry Gardner and Bill Parkinson. Also this year, modifications were made to the ECR ion source in order to produce greater currents of highly charged ions. Testing of the ion source was completed. Modifications were designed to extend the photon detection capabilities of the apparatus to shorter UV wavelengths, or EUV. Following the work on C(2+)(2s2p(sup 3)Pho(sup 0) yields 2p(sup 2)(sup 3)Rho), the extended UV detection capabilities will be used to measure the C(2+)(2s(sup 2)(sup 1)S yields 2s2p(sup 1)Rho(sup 0)) EIE cross section. The EUV modifications complement those of the new ion source, by enabling detection of EUV light generated by high charge state ions and putting us in a position to measure the excitation cross sections for more highly charged ions as well.

Parkinson, William↗
NASA NTRS2003

Visualization of Space-Time Ambiguities to be Explored by NASA GEC Mission with a Critique of Synthesized Measurements for Different GEC Mission Scenarios

The Grant supported research addressing the question of how the NASA Solar Terrestrial Probes (STP) Mission called Geospace electrodynamics Connections (GEC) will resolve space-time structures as well as collect sufficient information to solve the coupled thermosphere-ionosphere- magnetosphere dynamics and electrodynamics. The approach adopted was to develop a high resolution in both space and time model of the ionosphere-thermosphere (I-T) over altitudes relevant to GEC, especially the deep-dipping phase. This I-T model was driven by a high- resolution model of magnetospheric-ionospheric (M-I) coupling electrodynamics. Such a model contains all the key parameters to be measured by GEC instrumentation, which in turn are the required parameters to resolve present-day problems in describing the energy and momentum coupling between the ionosphere-magnetosphere and ionosphere-thermosphere. This model database has been successfully created for one geophysical condition; winter, solar maximum with disturbed geophysical conditions, specifically a substorm. Using this data set, visualizations (movies) were created to contrast dynamics of the different measurable parameters. Specifically, the rapidly varying magnetospheric E and auroral electron precipitation versus the slower varying ionospheric F-region electron density, but rapidly responding E-region density.

Sojka, Jan J.↗
NASA NTRS2018

Direct Probe of Dark Energy Interactions with a Solar System Laboratory: NASA Innovative Advanced Concepts (NIAC) - Phase 1 Final Report

In this NIAC (NASA Innovative Advanced Concepts) study, we embrace the challenge of direct detection of the galileon dark energy field in the Vainshtein model. We developed a mission concept to directly measure the galileon field using the solar system as a laboratory. The experiment scheme involves precise measurements of the trace of the total scalar force gradient tensor. A tetrahedral constellation off our spacecraft measures the "local" traces while orbiting about 1 AU (Astronomical Unit) away from the Sun and faraway from planets (Figure 1). The trace measurement is insensitive to the much stronger gravity field which satisfies the inverse square law and thus is traceless. Atomic test masses and atom interferometer measurement techniques are used as precise drag-free inertial references while laser ranging interferometers are employed to connect among atom interferometer pairs in spacecraft for the differential gradient force measurements. We conclude that such a mission is scientifically and technologically feasible. We show that a mission of 3-year measurement time would be able to provide high confidence statements (over 3 standard deviations) about the existence and strength of the cubic galileon field of the Sun. In addition, such a mission would also provide rich and diverse scientific data for testing any gravitational theory in general beyond the Newtonian gravity, hunting for ultra-light fields of dark matter, and detecting gravitational waves in the mid-frequency band between those of LIGO (Laser Interferometer Gravitational-Wave Observatory) and LISA (Laser Interferometer Space Antenna). For these reasons, we will term the mission concept Gravity Observation and Dark energy Detection Explorer in the Solar System (GODDESS).

Dark Energy↗
NASA NTRS1971

Mariner-Venus 1967

Detailed information on the spacecraft performance, mission operations, and tracking and data acquisition is presented for the Mariner Venus 1967 and Mariner Venus 1967 extension projects. Scientific and engineering results and conclusions are discussed, and include the scientific mission, encounter with Venus, observations near Earth, and cruise phase of the mission. Flight path analysis, spacecraft subsystems, and mission-related hardware and computer program development are covered. The scientific experiments carried by Mariner 5 were ultraviolet photometer, solar plasma probe, helium magnetometer, trapped radiation detector, S-band radio occultation, dual-frequency radio propagation, and celestial mechanics. The engineering experience gained by converting a space Mariner Mars 1964 spacecraft into one flown to Venus is also described.

Source record↗
NASA NTRS1976

The interpretations of ultraviolet observations of comets

The paper summarizes recent cometary UV observations, most of which were made in Ly-alpha light with instruments aboard earth-orbiting satellites. These include OAO-2 observations of comets Bennett and Tago-Sato-Kosaka, OGO-5 observations of comets Bennett and Encke, and numerous observations of comet Kohoutek. Models for the production of cometary hydrogen atoms are described, including the fountain, syndyname, and parent-daughter models. Calculations of emission line profiles and multiple-scattering effects are also discussed. Results of observations and interpretations are reviewed for each cited comet, far-UV observations in other emission lines are noted, and the use of comets as solar-wind probes is considered. It is concluded that the results of the present cometary Ly-alpha observations strongly support the concept of an icy conglomerate solid cometary nucleus and suggest water to be one of the most abundant molecules in comets.

Keller, H. U.↗
NASA NTRS1981

Diagnostic system design for the Ion Auxiliary Propulsion System (IAPS). Flight tests of two 8 cm mercury ion

The mechanical, thermal, electrical design and the ground test results of four types of detectors are explained. The DSS is designed to measure the thruster efflux material deposition and S/C potential relative to the local plasma in the vicinity of two 8 cm mercury ion thrusters. The DSS consists of two quartz crystal microbalance (QCM) detectors, one potential probe, nine solar cell arrays, seven ion collectors and two electronic packages.

Hurst, E. B.↗
NASA NTRS1981

The JOCR program

Observational data on large-scale plasma structures in comets is of value in (1) analyzing the interaction between the solar wind and comets, (2) using comets as solar wind probes, and (3) using comets as an astrophysical plasma laboratory with the CO+ plasma serving as tracers of the magnetic field. To obtain this data, the Joint Observatory for Cometary Research was built on South Baldy in the Magdalena Mountains west of Socorro, New Mexico, at an altitude of 10,615 feet. The telescope is a 14" f/2 Schmidt camera which records an 80 deg x 10 deg field onto 4 x 5 inch plates. The camera is designed for fixed focus operation, i.e., within design limits, the focus is not a function of temperature. A vacuum platen system allows the use of film for color photography. Sample observations of comets Kohoutek, West, Kobayashi-Berger-Milon and Bradfield are interpreted.

Brandt, J. C.↗
NASA NTRS1993

Investigation of passive atmospheric sounding using millimeter and submillimeter wavelength channels

Progress by investigators at the Georgia Institute of Technology in the development of techniques for passive microwave retrieval of water vapor, cloud, and precipitation parameters using millimeter- and sub-millimeter wavelength channels is reviewed. Channels of particular interest are in the tropospheric transmission windows at 90, 166, 220, 340, and 410 GHz and centered around the water vapor lines at 183 and 325 GHz. Collectively, these channels have potential application in high-resolution mapping (e.g., from geosynchronous orbit), remote sensing of cloud and precipitation parameters, and retrieval of water vapor profiles. During the period from 1 Jan. 1993 through 30 Jun. 1993 the Millimeter-wave Imaging Radiometer (MIR) completed data flights during a two-month long deployment in conjunction with TOGA/COARE. Coincident data was collected from several other ground-based, airborne, and satellite sensors, including the NASA/MSFC AMPR, MIT MTS, DMSP SSM/T-2 satellite, collocated radiosondes, ground- and aircraft-based radiometers and cloud lidars, airborne infrared imagers, solar flux probes, and airborne cloud particle sampling probes.

Gasiewski, A. J.↗