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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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NASA NTRS2022

Revisiting the Solar Research Cyberinfrastructure Needs: A White Paper of Findings and Recommendations

Solar and Heliosphere physics are areas of remarkable data-driven discoveries. Recent advances in high cadence, high-resolution multiwavelength observations, growing amounts of data from realistic modeling, and operational needs for uninterrupted science-quality data coverage generate the demand for a solar metadata standardization and overall healthy data infrastructure. This white paper is prepared as an effort of the working group “Uniform Semantics and Syntax of Solar Observations and Events” created within the “Towards Integration of Heliophysics Data, Modeling, and Analysis Tools” EarthCube Research Coordination Network (@HDMIEC RCN), with primary objectives to discuss current advances and identify future needs for the solar research cyberinfrastructure. The white paper summarizes presentations and discussions held during the special working group session at the EarthCube Annual Meeting on June 19th, 2020, as well as community contribution gathered during a series of preceding workshops and subsequent RCN working group sessions. The authors provide examples of the current standing of the solar research cyberinfrastructure, and describe the problems related to current data handling approaches. The list of the top-level recommendations agreed by the authors of the current white paper is presented at the beginning of the paper.

SMD↗
DOE OSTI2021

The Most Massive White Dwarfs in the Solar Neighborhood

We present an analysis of the most massive white dwarf candidates in the Montreal White Dwarf Database 100 pc sample. We identify 25 objects that would be more massive than 1.3M ⊙ if they had pure H atmospheres and CO cores, including two outliers with unusually high photometric mass estimates near the Chandrasekhar limit. We provide follow-up spectroscopy of these two white dwarfs and show that they are indeed significantly below this limit. We expand our model calculations for CO core white dwarfs up to M = 1.334 M ⊙ , which corresponds to the high-density limit of our equation-of-state tables, ρ = 109 g cm -3 . We find many objects close to this maximum mass of our CO core models. A significant fraction of ultramassive white dwarfs are predicted to form through binary mergers. Merger populations can reveal themselves through their kinematics, magnetism, or rapid rotation rates. We identify four outliers in transverse velocity, four likely magnetic white dwarfs (one of which is also an outlier in transverse velocity), and one with rapid rotation, indicating that at least 8 of the 25 ultramassive white dwarfs in our sample are likely merger products.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS2002

Hydrodynamic Models of Line-Driven Accretion Disk Winds III: Local Ionization Equilibrium

We present time-dependent numerical hydrodynamic models of line-driven accretion disk winds in cataclysmic variable systems and calculate wind mass-loss rates and terminal velocities. The models are 2.5-dimensional, include an energy balance condition with radiative heating and cooling processes, and includes local ionization equilibrium introducing time dependence and spatial dependence on the line radiation force parameters. The radiation field is assumed to originate in an optically thick accretion disk. Wind ion populations are calculated under the assumption that local ionization equilibrium is determined by photoionization and radiative recombination, similar to a photoionized nebula. We find a steady wind flowing from the accretion disk. Radiative heating tends to maintain the temperature in the higher density wind regions near the disk surface, rather than cooling adiabatically. For a disk luminosity L (sub disk) = solar luminosity, white dwarf mass M(sub wd) = 0.6 solar mass, and white dwarf radii R(sub wd) = 0.01 solar radius, we obtain a wind mass-loss rate of M(sub wind) = 4 x 10(exp -12) solar mass yr(exp -1) and a terminal velocity of approximately 3000 km per second. These results confirm the general velocity and density structures found in our earlier constant ionization equilibrium adiabatic CV wind models. Further we establish here 2.5D numerical models that can be extended to QSO/AGN winds where the local ionization equilibrium will play a crucial role in the overall dynamics.

Pereyra, Nicolas Antonio↗
DOE OSTI2020

White Earth Community Facilities Solar PV Project (Final Report)

Funded project was for the design, installation, and performance monitoring of 2 - 11.4 kW AC and 1-38.0 kW AC ground-mount solar installations for three tribal community facilities, for a total 60.8 kW AC, including a daycare facility and two community centers. Of in excess of 120 tribal buildings these facilities had showed the best promise for implementing solar, based upon site characteristics, roof loads, roof orientation and building size. The White Earth Nation seeks to move forward proactively to address the following project goals and objectives: 1) Reduction of energy costs, 2) Increasing energy security for Indian Tribes and tribal members, 3) Adding 60.8 KW in renewable energy generation (solar PV), 4) Offsets, reduces coal-fired electric energy demand by 76,397 kWh, 817,448 Source Energy Btu annually, and S) Meets the overall solar PV target set in the FOA.

14 SOLAR ENERGY↗
NASA NTRS1994

Flow properties of the solar wind obtained from white light data and a two-fluid model

The flow properties of the solar wind from 1 R(sub s) to 1 AU were obtained using a two fluid model constrained by density and scale height temperatures derived from white light observations, as well as knowledge of the electron temperature in coronal holes. The observations were obtained with the white light coronographs on SPARTAN 201-1 and at Mauna Loa (Hawaii), in a north polar coronal hole from 1.16 to 5.5 R(sub s) on 11 Apr. 1993. By specifying the density, temperature, Alfven wave velocity amplitude and heating function at the coronal base, it was found that the model parameters fit well the constraints of the empirical density profiles and temperatures. The optimal range of the input parameters was found to yield a higher proton temperature than electron temperature in the inner corona. The results indicate that no preferential heating of the protons at larger distances is needed to produce higher proton than electron temperatures at 1 AU, as observed in the high speed solar wind.

Habbal, Shadia Rifai↗
NASA NTRS2004

AZW-LA-II White Paint on Swift: Lessons Learned from First Time Flying on Spacecraft Radiators

AZ-Tek's AZW-LA-II low solar absorptance white paint was previously flown as a flight experiment, and is being flown as a calorimeter. However it has never been flown as a thermal coating of radiators on an operational spacecraft before. This paint has the lowest solar absorptance among all white paints, and a very small degradation. Its cost is many times more expensive than white paints that have a higher solar absorptance. To meet the thermal requirements of the Swift Burst Alert Telescope (BAT) Detector Array and X-Ray Telescope (XRT) focal plane camera assembly (FPCA) charged coupled device (CCD), AZW-LA-II is used as the thermal coating for the BAT and XRT radiators. This paper presents the lessons learned from flying this low solar absorptance white paint as a thermal coating of radiators on an operational spacecraft for the first time.

Choi, Michael K.↗
NASA NTRS1979

Optical counterpart of 2A0311-227

Spectrophotometric observations of the optical counterpart of the X-ray source 2A0311-227 are reported. A 1.3-m telescope associated with a photon-counting spectral scanner was used for observations in the range 4000 to 5800 A. Strong emission features are noted for H I, He II at 4686 A and the C III-N III blend at 4640-4650 A. Analyses of radial velocities show the star to be a spectroscopic binary with a period of 81.04 + or - 0.01 min, while blue and yellow light curves reveal variations in stellar color. Similarities between this binary and AM Herculis are noted and a model of a 1.2-solar mass white dwarf with a 0.2-solar mass companion at a separation of 0.7 solar radii is suggested.

Williams, G.↗
NASA NTRS1995

Flow properties of the solar wind obtained from white light data, Ulysses observations and a two-fluid model

Using the empirical constraints provided by observations in the inner corona and in interplanetary space. we derive the flow properties of the solar wind using a two fluid model. Density and scale height temperatures are derived from White Light coronagraph observations on SPARTAN 201-1 and at Mauna Loa, from 1.16 to 5.5 R, in the two polar coronal holes on 11-12 Apr. 1993. Interplanetary measurements of the flow speed and proton mass flux are taken from the Ulysses south polar passage. By comparing the results of the model computations that fit the empirical constraints in the two coronal hole regions, we show how the effects of the line of sight influence the empirical inferences and subsequently the corresponding numerical results.

Habbal, Shadia Rifai↗
NASA NTRS1985

Characteristics of the white-light source in the 1981 April 24 solar flare

Observations of the white-light solar flare event of April 24, 1981 are presented. The observations were carried out in the optical, hard X-ray, and radio wavelengths from land-based observatories and from the International Sun-Earth Explorer (ISEE-3) satellite. Time-intensity profiles were derived for three lines of continuum emissions. The derived profiles are interpreted in terms of the energetics of the flare, and the role of energetic electrons in the production of optical continuum emission is examined in detail.

Kane, S. R.↗
NASA NTRS1984

Spartan - Space at low-cost

Mission profiles and objectives of the Spartan Shuttle payload are described. Spartan was designed to provide extended observations normally carried out for only a few minutes using sounding rockets. The payload will be placed in co-orbit with the Orbiter by the RMS arm and controlled by a ground-based researcher or by an on-board program. Spartan features minimal battery power, batteries, and control systems and no redundancy. Thermal control is added because the flights last 100-1000 times as long as those on sounding rockets. Data are recorded by an on-board tape recorder and operations are controlled by an on-board microprocessor. Spartan 1 will carry a star-pointer and X-ray detectors for high energy astrophysics experiments. Spartan 2 will gather solar physics data in the form of temperatures of hydrogen gas and ions and electrons. Particle densities will also be monitored and a 43 cm solar telescope will produce UV and white light solar coronagraphs. UV spectroscopy of stars, clouds and galaxies will be performed by the Spartan 3 payload.

Source record↗
NASA NTRS1986

White-light movies of the solar photosphere from the SOUP instrument on Spacelab

Initial results are presented on solar granulation, pores and sunspots from the white-light films obtained by the Solar Optical Universal Polarimeter (SOUP) instrument in Spacelab 2. Several hours of movies were taken at various disk and limb positions in quiet and active regions. The images are diffraction-limited at 0.5 arcsec resolution and are, of course, free of atmospheric seeing and distortion. Properties of the granulation in magnetic and nonmagnetic regions are compared and are found to differ significantly in size, rate of intensity variation, and lifetime. In quiet sun, on the order of fifty-percent of the area has at least one 'exploding granule' occurring in it during a 25-min period. Local correlation tracking has detected several types of transverse flows, including systematic outflow from the penumbral boundary of a spot, motion of penumbral filaments, and cellular flow patterns of supergranular and mesogranular size. Feature tracking has shown that, in the quiet sun, the average granule fragment has a velocity of about one kilometer/second.

Title, A. M.↗
NASA NTRS1987

The origin of ultra-compact binaries

The origin of ultra-compact binaries composed of a neutron star and a low-mass (about 0.06 solar mass) white dwarf is considered. Taking account of the systemic losses of mass and angular momentum, it was found that a serious difficulty exists in the scenarios which involve tidal captures of a normal star (a main sequence star or a red giant) by a neutron star. This difficulty can be avoided if a red giant star is captured by a massive white dwarf (M is approx. greater than 1.2 solar masses), which becomes a neutron star through the accretion induced collapse.

Hachisu, Izumi↗
NASA NTRS1996

White Paper on SBUV/2 Solar Irradiance Measurements

The importance of solar irradiance measurements by the Solar Backscatter Ultraviolet, Model 2 (SBUV/2) instruments on NOAA's operational satellites is described. These measurements are necessary accurately monitor the long-term changes in the global column ozone amount, the altitude distribution of ozone in the upper stratosphere, and the degree to which ozone changes are caused by anthropogenic sources. Needed to accomplish these goals are weekly solar irradiance measurements at the operational ozone wavelengths, daily measurements of the Mg II proxy index, instrument-specific Mg II scale factors, and daily measurements of the solar spectral irradiance at photochemically important wavelengths. Two solar measurement schedules are provided: (1) a baseline schedule for all instruments except the NOAA-14 instrument and (2) a modified schedule for the NOAA-14 SBUV/2 instrument. This latter schedule is needed due to the NOAA-14 grating drive problems.

Hilsenrath, Ernest↗
NASA NTRS1999

Radio Tracking of a White-Light CME from Solar Corona to Interplanetary Medium

We analyze the radio emissions associated with a flare/CME event on the sun. For this solar event there were type II radio emissions observed in both the metric and decametric to kilometric wavelength regimes. By comparing the dynamics of the CME with that implied by the frequencies and frequency-drift rates of the type II radio emissions, it is concluded that only the decametric/kilometric type II radio emissions are associated with the CME. We provide the first direct one-to-one comparison between a CME and the associated type II radio emissions. The dynamics implied by the metric type II radio emissions suggest a distinct coronal shock, associated with the flare, which only produces radio emissions in the low corona.

Reiner, M. J.↗
NASA NTRS1977

Accretion of rotating fluids by barytropes - Numerical results for white-dwarf models

Numerical sequences of rotating axisymmetric nonmagnetic equilibrium models are constructed which represent the evolution of a barytropic star as it accretes material from a rotating medium. Two accretion geometries are considered - one approximating accretion from a rotating cloud and the other, accretion from a Keplerian disk. It is assumed that some process, such as Ekman spin-up or nonequilibrium oscillations, maintains nearly constant angular velocity along cylinders about the rotation axis. Transport of angular momentum in the cylindrically radial direction by viscosity is included. Fluid instabilities and other physical processes leading to enhancement of this transport are discussed. Particular application is made to zero-temperature white-dwarf models, using the degenerate electron equation of state. An initially nonrotating 0.566-solar-mass white dwarf is followed during the accretion of more than one solar mass of material. Applications to degenerate stellar cores, to mass-transfer binary systems containing white dwarfs, such as novae and dwarf novae, to Type I supernovae, and to galactic X-ray sources are considered.

Durisen, R. H.↗
NASA NTRS1980

CCD camera systems and support electronics for a White Light Coronagraph and X-ray XUV solar telescope

Two instruments, a White Light Coronagraph and an X-ray XUV telescope built into the same housing, share several electronic functions. Each instrument uses a CCD as an imaging detector, but due to different spectral requirements, each uses a different type. Hardware reduction, required by the stringent weight and volume allocations of the interplanetary mission, is made possible by the use of a microprocessor. Most instrument functions are software controlled with the end use circuits treated as peripherals to the microprocessor. The instruments are being developed for the International Solar Polar Mission.

Harrison, D. C.↗
NASA NTRS1991

How much hydrogen is there in a white dwarf?

Stratified hydrogen/helium envelope models in diffusive equilibrium are calculated for a 0.6-solar-mass white dwarf for effective temperatures between 10,000 and 80,000 K in order to investigate the observational constraints placed on the total hydrogen mass. Convective mixing is included ab initio in the calculations, and synthetic spectra are used for comparing these models with observational materials. It is shown that evolutionary changes in the surface composition of white dwarfs cannot be explained by a model in which a small amount of hydrogen floats to the surface from initially being mixed in the outer parts of a helium envelope. It is pointed out that the shape of the hydrogen lines can be used for constraining theories of convective overshoot.

Macdonald, James↗
NASA NTRS1990

Dynamic mass exchange in doubly degenerate binaries. I - 0.9 and 1.2 solar mass stars

The dynamic mass exchange process in doubly degenerate binaries was investigated using a three-dimensional numerical simulation of the evolution of a doubly degenerate binary system in which the primary is a 1.2-solar-mass white dwarf and the Roche lobe filling secondary is a 0.9-solar-mass dwarf. The results show that, in a little more than two orbital periods, the secondary is completely destroyed and transformed into a thick disk orbiting about the primary. Since only a very small fraction of the mass (0.0063 solar mass) escapes the system, the evolution of the binary results in the formation of a massive object. This object is composed of three parts, the initial white dwarf primary, a very hot pressure-supported spherical envelope, and a rotationally supported outer disk. The evolution of the system can be understood in terms of a simple analytical model where it is shown that the angular momentum carried by the mass during the transfer and stored in the disk determines the evolution of the system.

Benz, W.↗