Search NASA⌕ Search

SEARCH · Search NASA

Results for “Solar evolution”

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 397 records · Page 22
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Simulation of period doubling of recurrent solar wind structures

Based on satellite observations of a recurrent solar wind structure conducted in 1974, an MHD simulation model, and input functions generated from plasma and magnetic field data, the continuing evolution of the solar wind structure outside 5 AU is studied. The model uses the Rankine-Hugoniot relations to describe the jumps in flow properties across the shocks, and it treats shocks as surfaces of discontinuity with zero thickness. Two interaction processes (the collision and the merging of shocks) play important roles in restructuring the solar wind in the outer heliosphere. The simulation result shows that period doubling occurs between 5 and 10 AU. The recurrent solar wind appears to be a persistent new structure between 10 and 20 AU, and it consists of one merged interaction region per solar rotation.

Whang, Y. C.↗
NASA NTRS1990

The use of CCDs in the Space Telescope Imaging Spectrograph (STIS)

The present study describes the STIS instrument concept and the role and requirements of the CCD detectors. Specific required properties and the current status of the efforts to meet them are discussed. The goals of the STIS team include studies of the origin and evolution of the solar system, star formation, variable stellar phenomena, the nature and energy balance of the interstellar and intergalactic medium, and the origin and evolution of galaxies and their nuclear activity. The STIS operating modes (spectral range, resolving power, effective area, and angular range) and the optical arrangement to accomplish them are presented. The detective quantum efficiency of several candidate detector types are shown as a function of wavelength for the four STIS bands. Difficulties that arise in the use of CCDs are discussed. Consideration is given to the requirements imposed on STIS CCDs and to their performance.

Woodgate, Bruce E.↗
NASA NTRS1991

Report of the cosmic and heliospheric panel

The Cosmic and Heliospheric Branch proposes a bold new program for the years 1995 to 2010 that is centered on the following two themes: (1) the global heliosphere and interstellar space; and (2) cosmic particle acceleration and the evolution of matter. Within these major themes are more specific goals that have been studied and continue to be examined for a better understanding of their processes. These include: origin, structure, and evolution of the solar wind; interaction of the heliosphere, the solar wind, and the interstellar medium; fundamental microscopic and macroscopic plasma processes; acceleration and transport of energetic particles; and the origin and evolution of matter. Finally, the report summarizes a wide variety of proposed small and large space missions.

Mewaldt, Richard A.↗
NASA NTRS2012

Oxygen Isotope Compositions of the Kaidun Meteorite - Indications for Aqeuous Alteration of E-Chondrites

The Kaidun microbreccia is a unique meteorite due to the diversity of its constituent clasts. Fragments of various types of carbonaceous (CI, CM, CV, CR), enstatite (EH, EL), and ordinary chondrites, basaltic achondrites, and impact melt products have been described, and also several unknown clasts [1, and references therein]. The small mm-sized clasts represent material from different places and times in the early solar system, involving a large variety of parent bodies [2]; meteorites are of key importance to the study of the origin and evolution of the solar system, and Kaidun is a collection of a range of bodies evidently representing samples from across the asteroid belt. The parent-body on which Kaidun was assembled is believed to be a C-type asteroid, and 1-Ceres and the martian moon Phobos have been proposed [1-4]. Both carbonaceous (most oxidized) and enstatite (most reduced) chondrite clasts in Kaidun show signs of aqueous alterations that vary in type and degree and are most likely of pre-Kaidun origin [1, 4].

Ziegler, K.↗
NASA NTRS2015

Using Technology to Better Characterize the Apollo Sample Suite: A Retroactive PET Analysis and Potential Model for Future Sample Return Missions

From 1969-1972 the Apollo missions collected 382 kg of lunar samples from six distinct locations on the Moon. Studies of the Apollo sample suite have shaped our understanding of the formation and early evolution of the Earth-Moon system, and have had important implications for studies of the other terrestrial planets (e.g., through the calibration of the crater counting record) and even the outer planets (e.g., the Nice model of the dynamical evolution of the Solar System). Despite nearly 50 years of detailed research on Apollo samples, scientists are still developing new theories about the origin and evolution of the Moon. Three areas of active research are: (1) the abundance of water (and other volatiles) in the lunar mantle, (2) the timing of the formation of the Moon and the duration of lunar magma ocean crystallization, (3) the formation of evolved lunar lithologies (e.g., granites) and implications for tertiary crustal processes on the Moon. In order to fully understand these (and many other) theories about the Moon, scientists need access to "new" lunar samples, particularly new plutonic samples. Over 100 lunar meteorites have been identified over the past 30 years, and the study of these samples has greatly aided in our understanding of the Moon. However, terrestrial alteration and the lack of geologic context limit what can be learned from the lunar meteorites. Although no "new" large plutonic samples (i.e., hand-samples) remain to be discovered in the Apollo sample collection, there are many large polymict breccias in the Apollo collection containing relatively large (approximately 1 cm or larger) previously identified plutonic clasts, as well as a large number of unclassified lithic clasts. In addition, new, previously unidentified plutonic clasts are potentially discoverable within these breccias. The question becomes how to non-destructively locate and identify new lithic clasts of interest while minimizing the contamination and physical degradation of the samples.

Zeigler, R. A.↗
NASA NTRS1982

Evolution of giant gaseous protoplanets embedded in the primitive solar nebula

In contrast to earlier evolutionary calculations, which assumed that protoplanets are isolated, the present spherically symmetric approximation for a protoplanet of one Jovian mass during the early phase of quasi-static contraction invokes a time-dependent surface boundary condition that simulates physical conditions in an evolving primitive solar nebula. Assuming in a first set of calculations that the protoplanet is surrounded by a thermal bath whose temperature varies with time, and whose pressure is small and constant, results show evaporation and complete dispersal of the object. A second set of calculations varies both temperature and pressure at the surface with time, according to solar nebula models, and yields an acceleration or retardation of evolution, relative to that of an isolated protoplanet, depending on the relative entropy of the nebula and the protoplanet's outer layers. Processes by which terrestrial planets can form in the cores of giant gaseous protoplanets are discussed.

Cameron, A. G. W.↗
DOE OSTI2025

Extreme Heating of Minor Ions in Imbalanced Solar-wind Turbulence

Minor ions in the solar corona are heated to extreme temperatures, far in excess of those of the electrons and protons that comprise the bulk of the plasma. These highly nonthermal distributions make minor ions sensitive probes of the collisionless processes that heat the corona and power the solar wind. The recent discovery of the "helicity barrier" offers a mechanism in which imbalanced Alfvénic turbulence in low-β plasmas preferentially heats protons over electrons, generating high-frequency, proton-cyclotron-resonant fluctuations. We use the hybrid-kinetic particle-in-cell code Pegasus++ to drive imbalanced Alfvénic turbulence in a 3D low-β plasma with additional passive ion species, He 2+ and O 5+ . A helicity barrier naturally develops, followed by clear phase-space signatures of oblique proton-cyclotron-wave heating and Landau-resonant heating from the imbalanced Alfvénic fluctuations. The former results in characteristically arced ion velocity distribution functions, whose non-bi-Maxwellian features are shown by linear ALPS calculations to be critical to the heating process. Additional features include a steep transition-range electromagnetic spectrum, proton-cyclotron waves propagating in the direction of the imbalance, significantly enhanced proton-to-electron heating ratios, ion temperatures that are considerably more perpendicular with respect to magnetic field, and extreme heating of heavier species in a manner consistent with mass scalings inferred from spacecraft measurements. None of these features are realized in an otherwise equivalent simulation of balanced turbulence. If seen simultaneously in the fast solar wind, these signatures of the helicity barrier would testify to the necessity of incorporating turbulence imbalance in a complete theory for the evolution of the solar wind.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS2008

Solar Probe Plus: Report of the Science and Technology Definition Team

Solar Probe+ will be an extraordinary and historic mission, exploring what is arguably the last region of the solar system to be visited by a spacecraft, the Sun s outer atmosphere or corona as it extends out into space. Approaching as close as 9.5 RS* (8.5 RS above the Sun s surface), Solar Probe+ will repeatedly sample the near-Sun environment, revolutionizing our knowledge and understanding of coronal heating and of the origin and evolution of the solar wind and answering critical questions in heliophysics that have been ranked as top priorities for decades. Moreover, by making direct, in-situ measurements of the region where some of the most hazardous solar energetic particles are energized, Solar Probe+ will make a fundamental contribution to our ability to characterize and forecast the radiation environment in which future space explorers will work and live.

Source record↗
NASA NTRS1982

Heating of the corona and solar wind by switch-on shocks

The possibility is examined that the corona is heated by a train of weak switch-on shocks which are formed in the chromosphere from a train of Alfven waves, and which subsequently enter the corona from below. New results for the shock train propagation and dissipation and the resultant coronal heating are derived. It is shown that most of the energy in the shock train can be dissipated within one or two solar radii above the coronal base. A train of switch-on shocks therefore represents a viable coronal heating mechanism. The results are generalized to switch-on shocks in the solar wind. It is shown that such shocks can dissipate rapidly, but it is concluded that they are not the dominant factor governing the evolution of the solar wind turbulence.

Hollweg, J. V.↗
NASA NTRS1992

Solar prediction analysis

Solar Activity prediction is essential to definition of orbital design and operational environments for space flight. This task provides the necessary research to better understand solar predictions being generated by the solar community and to develop improved solar prediction models. The contractor shall provide the necessary manpower and facilities to perform the following tasks: (1) review, evaluate, and assess the time evolution of the solar cycle to provide probable limits of solar cycle behavior near maximum end during the decline of solar cycle 22, and the forecasts being provided by the solar community and the techniques being used to generate these forecasts; and (2) develop and refine prediction techniques for short-term solar behavior flare prediction within solar active regions, with special emphasis on the correlation of magnetic shear with flare occurrence.

Smith, Jesse B.↗
NASA NTRS1994

Meteoritical Society Annual Meeting, 57th, Prague, Czech Republic, July 25-29, 1994

Ranging in size from mere grains and palm-size stones to boulders and many-mile- wide hunks of rock, meteorites hold many secrets of our solar system, and indeed of our universe. The 57th Annual Meeting of the Meteoritical Society discussed many aspects of this fascinating 'chunk' of the evolution of the Solar System. Topics covered included: chemical composition, meteorite types, meteorite age determination, meteorite origins, and find locations, as well as a multitude of other important subjects.

Source record↗
NASA NTRS1995

Statistical properties of the solar wind

We now have spacecraft observations spanning more than a complete 22-year solar cycle. PVO at Venus, IMP 8 at Earth, and Voyager 2 and Pioneers 10 and 11 in the outer heliosphere provide many years of data from locations scattered through the heliosphere. These large data sets enable us to look at the solar wind velocity, density, temperature and flow angles on a statistical basis. Comparison of results at the different locations will provide information on the evolution of the solar wind with radial distance and variation with latitude.

Richardson, J. D.↗
NASA NTRS2002

Comparison of the Effects of Wave-Particle Interactions and the Kinetic Suprathermal Electron Population on the Acceleration of the Solar Wind

Kinetic effects due to wave-particle interactions and suprathermal electrons have been suggested in the literature as possible solar wind acceleration mechanisms. Ion cyclotron resonant heating, in particular, has been associated with some qualitative features observed in the solar wind. In terms of solar wind acceleration, however, it is interesting to compare the kinetic effects of suprathermal electrons with those due to the wave-particle interactions. The combined effects of the two acceleration mechanisms on the fast solar wind have been studied by Tam and Chang (1999a,b). In this study. we investigate the role of the suprathermal electron population in the acceleration of the solar wind. Our model follows the global kinetic evolution of the fast solar wind under the influence of ion cyclotron resonant heating, while taking into account Coulomb collisions, and the ambipolar electric field that is consistent with the particle distributions themselves. The kinetic effects due to the suprathermal electrons, which we define to be the tail of the electron distributions, can be included in the model as an option. By comparing the results with and without the inclusion of the suprathermal electron effects, we determine the relative importance of suprathermal electrons and wave-particle interactions in driving the solar wind. We find that although suprathermal electrons enhance the ambipolar electric potential in the solar wind considerably, their overall influence as an acceleration mechanism is relatively insignificant in a wave-driven solar wind.

Tam, S. W. Y.↗
NASA NTRS2014

The Use, Evolution and Lessons Learnt of Deployable Static Solar Array Mechanisms

This paper focuses on the mechanisms incorporated into SSTL's static deployable arrays; namely the sprung-hinges and hold down and release mechanism (HDRM). Combined, the HDRM and hinges form the hold down release system (HDRS). The deployable static solar array HDRS has been successfully used on several missions, first launched upon the DMC-CFESAT spacecraft in 2007 for a U.S. customer (Figure 1), and later used on DMC-UK2 and EXACTVIEW-1 launched in 2009 and 2012, respectively. The simple, robust and low-cost solution HDRS has been evident in allowing missions to satisfy an ever increasing power demand, allowing the solar arrays to increase in size and have a preferable sun angle for increased cell efficiency. The system is now being employed on the first mission out of SSTL's U.S. office (SST-US) on the Orbital Test Bed platform. This paper shall cover details of the original design and development program, problems incurred on latter missions, and evolution of the HDRS for the present Orbital Test Bed mission. Both the original development and recent evolutions have taken place in rapid timescales, to satisfy the high-turnaround of SSTL missions.

Ferris, Mark↗
NASA NTRS1977

The application of Fourier transform spectroscopy to the remote identification of solids in the solar system

The techniques of Fourier transform spectroscopy combined with large aperture telescopes and advances in detector technology now permit infrared (at a wavelength greater than 1 micron) observations of the surfaces of small solar system objects such as asteroids and satellites. The results demonstrate that this activity can produce important new compositional information related to the origin and evolution of the solar system. The detection of water ice in Saturn's rings and on some of the satellites of Jupiter and Saturn confirm expectations that ices are important mineralogical components in the chemistry of the outer solar system. More recent studies of the mineralogical composition of the surfaces of asteroids provide a new observational link to the origin of meteorites and the early thermal history of the solar system. These results have been dependent upon supporting laboratory studies of the spectral behavior of ices and minerals to define the potential, and limitations, of the method. Since many of the astronomical observations have been exploratory in nature, prospects are good that continued refinement of the techniques will lead to additional insights.

Larson, H. P.↗
NASA NTRS1993

Recondensation of chondritic material in the early solar system: Results of thermodynamic simulation

We have performed a thermodynamic simulation of the recondensation of evaporated meteoritic material. We suggest that evaporation and recondensation occurred in impact events during the intercollision of planetesimals during the early evolution of the solar system. The source materials adopted for our model are the chondrites CI Orgueil and H5 Richardton. These chondrites are representative examples of the two extremes regarding volatile content and oxidation state. We calculated equilibrium mineral compositions of the closed systems of the Orgueil's and Richardton's elemental composition at the P-T conditions characteristic of the explosion cloud formed at a planetesimal collision. The P-T conditions are as follows: 10(exp -4) bar, and 1500 and 2000 K. The results are presented.

Dorofeyeva, V. A.↗
NASA NTRS1989

The age of the Galactic disk - Inflow, chemical evolution, astration, and radioactivity

Theoretical models of Galactic evolution and observational data on the age of the Galaxy are compared, with a focus on recent results. Topics addressed include the infall of material and its effects on the age-metallicity relation, the distribution of metallicity, the present gas fraction and metallicity, and the age spectrum of interstellar nuclei; the chemical evolution of the solar neighborhood; the key results of nuclear cosmochronology; and astration effects on Galactic age. It is found that both nuclear cosmochronology and detailed stellar and Galactic evolution models tend to support an age of 12-16 Gyr.

Clayton, Donald D.↗
NASA NTRS2014

Astromaterials Research Office (KR) Overview

The fundamental goal of our research is to understand the origin and evolution of the solar system, particularly the terrestrial, "rocky" bodies. Our research involves analysis of, and experiments on, astromaterials in order to understand their nature, sources, and processes of formation. Our state-of-the-art analytical laboratories include four electron microbeam laboratories for mineral analysis, four spectroscopy laboratories for chemical and mineralogical analysis, and four mass spectrometry laboratories for isotopic analysis. Other facilities include the experimental impact laboratory and both 1-atm gas mixing and high-pressure experimental petrology laboratories. Recent research has emphasized a diverse range of topics, including: Study of the solar system's primitive materials, such as carbonaceous chondrites and interplanetary dust; Study of early solar system chronology using short-lived radioisotopes and early nebular processes through detailed geochemical and isotopic characterizations; Study of large-scale planetary differentiation and evolution via siderophile and incompatible trace element partitioning, magma ocean crystallization simulations, and isotopic systematics; Study of the petrogenesis of Martian meteorites through petrographic, isotopic, chemical, and experimental melting and crystallization studies; Interpretation of remote sensing data, especially from current robotic lunar and Mars missions, and study of terrestrial analog materials; Study of the role of organic geochemical processes in the evolution of astromaterials and the extent to which they constrain the potential for habitability and the origin of life.

Draper, David S.↗