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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 271 records · Page 15

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NASA NTRS2010

NASA Goddard Space Flight Center, on Behalf of the Fermi Large Area Telescope Collaboration

Because high-energy gamma rays can be produced by processes that also produce neutrinos, the gamma-ray survey of the sky by the Fermi (Gamma-ray Space Telescope offers a view of potential targets for neutrino observations. Gamma-ray bursts. Active Galactic Nuclei, and supernova remnants are all sites where hadronic, neutrino-producing interactions are plausible. Pulsars, pulsar wind nebulae, and binary sources are all phenomena that reveal leptonic particle acceleration through their gamma-ray emission. While important to gamma-ray astrophysics, such sources are of less interest to neutrino studies. This talk will present a broad overview of the constantly changing sky seen with the Large Area Telescope (LAT)on the Fermi spacecraft.

Thompson, David J.↗

NASA NTRS2011

Fermi Gamma-Ray Space Telescope: Highlights of the GeV Sky

Because high-energy gamma rays can be produced by processes that also produce neutrinos. the gamma-ray survey of the sky by the Fermi Gamma-ray Space Telescope offers a view of potenl ial targds for neutrino observations. Gamma-ray bursts. active galactic nuclei, and supernova remnants are all sites where hadronic, neutrino-producing interactions are plausible. Pulsars, pulsar wind nebulae, and binary sources are all phenomena that reveal leptonic particle acceleration through their gamma-ray emission. \Vhile important to gamma-ray astrophysics. such sources are of less interest to neutrino studies. This talk will present a broad overview of the constantly changing sky seen with the Large Area Telescope (LAT) on the Fermi spacecraft.

Thomspon, D. J.↗

NASA NTRSDate not supplied

Effect of Space Radiation on TES Detectors Performance

The Athena mission and its X-IFU instrument (X-ray Integral Field Unit) will be positioned at the Sun-Earth Lagrangian point L1, where it will be subject to solar wind (low flux plasma of 95% protons and 5% alpha particles) with energy below 0.1 MeV, and to galactic cosmic rays and solar flares (energetic protons, alpha particles, and electrons) with energies up to hundreds of MeV for protons and the GeV for heavier ions. Some of these particles will go through the satellite and hit the focal plane assembly and hence the detectors. These detectors will be TES (Transition-edge sensor) microcalorimeters, flown for the first time in such an environment. In order to ensure the performance of this type of detectors throughout the duration of such mission, it is critical to study the impact of the radiation on their behavior. Indeed, although a lot of reference material exist for semiconductor detectors such as CCDs, little is currently known about the impact of radiation on TES detectors. These energetic events could cause local heating or damage to the detectors and affect their performance. In this work, we describe how we designed a test campaign to assess the impact of L1 radiation on TES detectors for Athena/X-IFU-like missions and present the results of the tests. Analyses includes assessing changes in the pulse shapes and energy resolution of the detectors measured at 55 mK after several radiation dose steps performed at 4 K.

Sophie Beaumont↗

NASA NTRS1991

Carbon and nitrogen abundances in the BN supergiant HD 93840, and their implications for normal Galactic supergiants

It is demonstrated how carbon and nitrogen abundances of luminous B stars can be determined by a combined analysis of their UV photospheric and wind lines. It is shown that HD 93840 has nearly the same temperature and surface gravity as the normal B1 Ib star Zeta Per. These two stars are compared on the basis of their UV photospheric silicon spectra and the differences in their photospheric CNO and metallic lines are discussed. A quantitative comparison between the wind profiles of the two stars is made. A simple model for the compositions of both atmospheres is used to derive the fraction of material in each atmosphere which has undergone CNO processing. It is argued that the enriched material must have resided in a nuclear burning core for only a very short time. Best estimates of 0.09 + or - 0.07 and 0.90 + or - 0.1 are made for the carbon abundances relative to cosmic ones for HD 93840 and Zeta Per, respectively.

Massa, D.↗

NASA NTRS1990

On the nature and implications of starburst-driven galactic superwinds

Optical spectroscopic data are presented on the ionized nebulae associated with 14 galaxies that are strong far-IR emitters. It is found that the data provide both qualitative and quantitative support for the 'superwind' model in which the kinetic energy provided by SNe and winds from massive stars in a central starburst drives a large-scale outflow that can shock heat and accelerate ambient interstellar and circumgalactic gas. Clear kinematic signatures of an outflow along the galaxy's minor axis are found for the three nearest far-IR galaxies (FIRGs). The FIRG nebulae are highly overpressured relative to the Galactic ISM, with the pressure dropping systematically with distance from the nucleus. Superwinds are energetically adequate to power both the observed optical and X-ray nebulae, and the relative emission-line intensities and their radial variations are consistent with ionization by wind-driven shocks, but not with photoionization by normal O stars or an AGN. The possible astrophysical implications of superwinds are discussed.

Heckman, Timothy M.↗

NASA NTRS1981

Correlation of the cosmic-ray intensity with solar-terrestrial parameters

Results are presented of numerical simulations of cosmic ray drift due to perturbations in the interplanetary medium affecting solar-terrestrial parameters. Computations were performed for a model spherical heliosphere of radius 25 AU, with an interplanetary magnetic field in the shape of an Archimedean spiral with magnitude of 5 gamma at 1 AU, corresponding to a wind velocity of 400 km/sec, and diffusion coefficients corresponding to the assumption that the parallel mean free path is somewhat larger han the cyclotron radius at earth orbit, and its spatial dependence is proportional to the gyroradius. It is found that perturbations in the heliospheric equatorial regions affect galactic cosmic rays more effectively when the Northern Hemisphere heliospheric magnetic field is directed inward rather than outward, with perturbations in the parallel drift coefficient more effective than perturbations in solar wind velocity or perpendicular drift velocity. Results are consistent with the observed variation of the correlation between the geomagnetic aa index and the neutron monitor counting rate on Mt. Washington with the solar cycle.

Jokipii, J. R.↗

NASA NTRS2003

Wind Observations of Anomalous Cosmic Rays from Solar Minimum to Maximum

We report the first observation near Earth of the time behavior of anomalous cosmic-ray N, O, and Ne ions through the period surrounding the maximum of the solar cycle. These observations were made by the Wind spacecraft during the 1995-2002 period spanning times from solar minimum through solar maximum. Comparison of anomalous and galactic cosmic rays provides a powerful tool for the study of the physics of solar modulation throughout the solar cycle.

Reames, D. V.↗

NASA NTRS1990

Ulysses Launch

Ulysses is a joint mission between the United States National Aeronautics and Space Administration (NASA) and the European Space Agency (ESA) to explore the heliosphere over the full range of solar latitudes, especially in the polar regions. The goal of the Ulysses mission is to provide an accurate assessment of our total solar environment. This collaborative ESA/NASA mission will, for the first time, explore the heliosphere -- the region of space that is dominated by the Sun-- within a few astronomical units of the Sun over the full range of heliographic latitudes. The path followed by the spacecraft, using a Jupiter gravity-assist to achieve a trajectory extending to high solar latitudes, will enable the highly sophisticated scientific instruments on board to make measurements in the uncharted third dimension of the heliosphere. The Ulysses spacecraft will carry nine scientific instruments to measure the properties of the solar corona, the solar wind, the Sun/wind interface, the heliospheric magnetic field, solar radio bursts, plasma waves, solar X-rays, solar and galactic cosmic rays, and the interplanetary/interstellar neutral gas and dust. Scientists will take advantage of the enormous distance between the spacecraft and the Earth to perform astrophysical measurements and to search for gravitational waves. In conjunction with instrumentation on Earth-orbiting spacecraft, Ulysses will help to precisely locate the mysterious sources of cosmic gamma bursts. The results obtained will help to solve outstanding problems in solar and heliospheric physics, while undoubtedly revealing new and unanticipated phenomena.

Source record↗

NASA NTRS1980

Solar cycle changes in the polar solar wind

It is noted that although the 11 year solar cycle was first recognized in 1843, it is still only poorly understood. Further, while there are satisfactory models for the magnetic variations, the underlying physics is still obscure. New observations on the changing three-dimensional form of the solar wind are presented which help relate some of the modulations observed in geomagnetic activity, the ionosphere, and the flux of galactic cosmic rays.

Coles, W. A.↗

NASA NTRS1983

The ISPM Mission - Science objectives and mission overview

The International Solar Polar Mission (ISPM) will, for the first time, allow exploration of the heliosphere within a few astronomical units of the sun over the full range of heliographic latitudes. The prime mission objective is to study, as a function of solar latitude, the properties of the interplanetary medium and solar corona. The scientific instrumentation is designed to explore, in the third heliospheric dimension, the properties of the solar wind, the sun/wind interface, the heliospheric magnetic field, solar radio bursts and plasma waves, solar X-rays, solar and galactic cosmic rays, and interplanetary/interstellar neutral gas and dust. ISPM will also detect cosmic gamma-ray bursts and search for gravitational waves. ISPM is a cooperative mission carried out jointly by ESA and NASA, to be launched in May 1986 and utilising a Jupiter gravity-assist to achieve a high-solar-latitude trajectory.

Wenzel, K.-P.↗

NASA NTRS1984

The galaxy as a self-regulated star-forming system - The case of the OB associations

It is proposed that the energy and momentum injected from OB associations can act as the regulators of high-mass star formation throughout the disk of a spiral galaxy. The mechanism, interacting blast waves driven by supernovae and stellar winds, leads to a generalized Schmidt law for the star formation rate and could explain in a natural way the galactic gradients of metals and star formation rate. The formation of massive stars is determined by the average ambient density in the disk while low-mass star formation is regulated by the density in molecular clouds. That is, there are two modes of star formation, but the physical mechanism is the same in both cases.

Franco, J.↗

NASA NTRS1989

Ulysses - The first high-latitude heliospheric mission

The Ulysses mission will, for the first time, explore the heliosphere within a few astronomical units of the sun over the full range of heliographic latitudes, thereby providing the first characterization of the uncharted third dimension. Highly sophisticated scientific instrumentation carried on board the spacecraft is designed to measure the properties of the solar wind, the sun/wind interface, the heliospheric magnetic field, solar radio bursts and plasma waves, solar X-rays, solar and galactic cosmic rays, and interplanetary/interstellar neutral gas and dust. This collaborative ESA/NASA mission, scheduled for launch in October 1990, will use a Jupiter gravity-assist to achieve a trajectory extending to high solar latitudes /1,2/.

Wenzel, K.-P.↗

NASA NTRS2017

Interplanetary Coronal Mass Ejection Observed at STEREO-A, Mars, Comet 67P/Churyumov-Gerasimenko, Saturn,and New Horizons En Route to Pluto: Comparison of Its Forbush Decreases at 1.4, 3.1, and 9.9 AU

We discuss observations of the journey throughout the Solar System of a large interplanetary coronal mass ejection (ICME) that was ejected at the Sun on 14 October 2014. The ICME hit Mars on 17 October, as observed by the Mars Express, Mars Atmosphere and Volatile EvolutioN Mission (MAVEN), Mars Odyssey, and Mars Science Laboratory (MSL) missions, 44 h before the encounter of the planet with the Siding-Spring comet, for which the space weather context is provided. It reached comet 67P/Churyumov-Gerasimenko, which was perfectly aligned with the Sun and Mars at 3.1 AU, as observed by Rosetta on 22 October. The ICME was also detected by STEREO-A on 16 October at 1 AU, and by Cassini in the solar wind around Saturn on the 12 November at 9.9 AU. Fortuitously, the New Horizons spacecraft was also aligned with the direction of the ICME at 31.6 AU. We investigate whether this ICME has a nonambiguous signature at New Horizons. A potential detection of this ICME by Voyager 2 at 110-111 AU is also discussed. The multispacecraft observations allow the derivation of certain properties of the ICME, such as its large angular extension of at least 116deg, its speed as a function of distance, and its magnetic field structure at four locations from 1 to 10 AU. Observations of the speed data allow two different solar wind propagation models to be validated. Finally, we compare the Forbush decreases (transient decreases followed by gradual recoveries in the galactic cosmic ray intensity) due to the passage of this ICME at Mars, comet 67P, and Saturn.

Witasse, O.↗

NASA NTRS2021

Evidence from Galactic Cosmic Rays That the Sun Has Likely Entered A Secular Minimum in Solar Activity

Since the beginning of the space age, the Sun has been in a multi-cycle period of elevated activity (secular maximum). This secular maximum is the longest in the last 9300 years. Since the end of solar cycle 21 (SC21), however, the Sun has shown a decline in over-all activity, which has remarkably increased the fluxes of galactic cosmic rays (GCRs). Here, we investigate the correlation between the modulation of GCRs, the heliospheric magnetic field, and solar wind speed for the last 24 solar cycles to find trends that can potentially be used to predict future solar activity. Specifically, we develop a tool for predicting future magnetic field intensity, based on the hysteresis in the GCR variation, during the last phases of the current cycle. This method estimates that SC25 will be as weak as or weaker than SC24. This would mean that the Sun has likely entered a secular minimum, which, according to historical records, should last for another two cycles (SC2527and SC26).

Solar cycles↗

NASA NTRS1980

Nature of the fossil evidence - Moon and meteorites

The nature of the fossil evidence to be found in extraterrestrial materials concerning the history of solar activity is reviewed. The various types of lunar rocks and meteorites containing evidence of exposure to solar radiations are distinguished, including igneous rocks, breccias, glassy agglutinates, single mineral crystals, carbonaceous meteorites, and the Antarctic meteorites, some of which fell to earth as much as a million years ago. The characteristic effects of energetic particles from space in materials are then examined, including ion implantation and surface radiation damage to a depth of several hundred A by the solar wind, radioactivity, electron trapping and track production induced by solar flares to depths from millimeters to centimeters, and spallation due to galactic cosmic rays at depths from centimeters to meters. Complications in the interpretation of radiation exposure histories represented by dynamic surface processes, the nonsolar origin of some trapped elements, and difficulties in determining the duration and epoch of surface exposure of individual crystals are also noted.

Walker, R. M.↗

NASA NTRS1981

A meeting with the universe: Science discoveries from the space program

A general history of space exploration is presented. The solar system is discussed. The Sun-Earth relationship is considered, including magnetic fields, solar wind, the magnetosphere, and the Sun-weather relationship. The universe beyond the solar system is discussed. Topics include stellar and galactic evolution, quasars and intergalactic space. The effects of weightlessness and ionizing radiation on human beings are considered. The possibility of extraterrestrial life is discussed. Lunar and planetary exploration, solar-terrestrial physics, astrophysics, biomedical research and exobiology are reviewed. Numerons color illustrations are included.

French, B. M.↗

NASA NTRS1994

Implosive accretion and outbursts of active galactic nuclei

A model and simulation code have been developed for time-dependent axisymmetric disk accretion onto a compact object including for the first time the influence of an ordered magnetic field. The accretion rate and radiative luminosity of the disk are naturally coupled to the rate of outflow of energy and angular momentum in magnetically driven (+/- z) winds. The magnetic field of the wind is treated in a phenomenological way suggested by self-consistent wind solutions. The radial accretion speed u(r, t) of the disk matter is shown to be the sum of the usual viscous contribution and a magnetic contribution proportional to r(exp 3/2)(B(sub p exp 2))/sigma, where B(sub p)(r,t) is the poloidal field threading the disk and sigma(r,t) is the disk's surface mass density. An enhancement or variation in B(sub p) at a large radial distance leads to the formation of a soliton-like structure in the disk density, temperature, and B-field which propagates implosively inward. The implosion gives a burst in the power output in winds or jets and a simultaneous burst in the disk radiation. The model is pertinent to the formation of discrete fast-moving components in jets observed by very long baseline interferometry. These components appear to originate at times of optical outbursts of the active galactic nucleus.

Lovelace, R. V. E.↗

NASA NTRS1989

On the nature of emission-line clouds of quasars and active galactic nuclei

It is proposed that the clouds responsible for the emission lines in AGN and QSOs are stratified and not uniform in density. Specifically, it is suggested that they are winds from evolved stars, in particular red giants. This assumption appears to solve, in straightforward fashion, several problems concerning the origin, dynamics, and response of these clouds to changes in the continuum luminosity, while preserving the most successful feature of the current two-phase equilibrium photoionization models.

Kazanas, Demosthenes↗