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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 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

A white-light /Fe X/H-alpha coronal transient observation to 10 solar radii

Multitelescope observations of the coronal transient of April 15-16, 1980 provide simultaneous data from the Solar Maximum Mission Coronagraph/Polarimeter, the Solwind Coronagraph, and the new Emission line Coronagraph of the Sacramento Peak Observatory. An eruptive prominence-associated white light transient is for the first time seen as an unusual wave or brightening in Fe X 6374 A (but not in Fe XIV 5303 A). Several interpretations of this fleeting enhancement are offered. The prominence shows a slowly increasing acceleration which peaks at the time of the Fe event. The white light loop transient surrounding the prominence expands at a well-documented constant speed to solar radii, with an extrapolated start time at zero height coincident with the surface activity. This loop transient exemplifies those seen above 1.7 solar radii, in that leading the disturbance is a bright N(e)-enhanced) loop rather than a dark one. This is consistent with a report of the behavior of another eruptive event observed by Fisher and Poland (1981) which began as a density depletion in the lower corona, with a bright loop forming at greater altitudes. The top of the bright loop ultimately fades in the outer corona while slow radial growth continues in the legs.

Wagner, W. J.↗
NASA NTRS1972

Velocity of the solar wind as determined from interplanetary scintillations.

The method of smooth perturbations is used to derive the equations for interplanetary scintillation in a (statistically) spherically symmetric solar wind with constant wind velocity. The expressions, valid in the limit of small scintillation index, are used to discuss the relation between the radial wind velocity and the observed projected velocity of the scintillation pattern. It is found that the pattern velocity is systematically less than the wind velocity by a substantial fraction, depending on the radial variation of the density fluctuations. If the fluctuations fall off as 1/r-squared the correction is 18 percent, whereas if the fluctuations are proportional to 1/r the correction is 57 percent. The effects may be even more severe if the solar wind is not spherically symmetric.

Jokipii, J. R.↗
NASA NTRS1980

Glycol/water evacuated-tube solar collector

Report describes performance of 8 tube and 10 tube commercially produced solar collectors. Tests include thermal efficiency, time constant for temperature drop after solar flux is cut, change in efficiency with Sun angle, and temperature rise if circulation is stopped.

Source record↗
NASA NTRS2014

LADEE UVS (UltraViolet Visible Spectrometer) and the Search for Lunar Exospheric Dust: A Detailed Spectral Analysis

The Lunar Atmosphere and Dust Environment Explorer (LADEE) executed science observations in lunar orbit spanning 2013-Oct-16- 2014-04-18 UT. LADEE's Ultraviolet/Visible Spectrometer (UVS) studies the composition and temporal variations of the tenuous lunar exosphere and dust environment, utilizing two sets of optics: a limb-viewing telescope, and a solar-viewer. The limb-viewing telescope observes illuminated dust and emitting gas species while the Sun is just behind the lunar limb. The solar viewer, with its diffuser, allows UVS to also stare directly at the solar disk as it approaches the limb, sampling progressively lower exosphere altitudes. Solar viewer "Occultation" activities occur at the lunar sunrise limb, as the LADEE spacecraft passes into the lunar night side, facing the Sun (the spacecraft orbit is near-equatorial retrograde). A loss of transmission of sunlight occurs by the occultation of dust grains along the line-of-sight. So-called "Inertial Limb" activities have the limb-viewing telescope pointed at the lit exosphere just after the Sun has set. Inertial Limb activities follow a similar progression of diminishing sampling altitudes but hold the solar elongation angle constant so the zodiacal light contribution remains constant while seeking to observe the weak lunar horizon glow. On the dark side of the moon, "Sodium Tail" activities pointed the limb-viewing telescope in the direction of the Moon's sodium tail (similar to anti-sunward), during different lunar phases. Of the UVS data sets, these show the largest excess of scattered blue light, indicative of the presence of small (approximately 100 nm) dust grains in the tail. Correlations are sought between dust in the sodium tail and meteor streams and magnetotail crossings to investigate impact- versus electrostatic-lofting. Once lofted, nanoparticles can become charged and picked up by the solar wind. The LADEE UVS Occultation, Inertial Limb, and Sodium Tail spectral datasets provide evidence of a lunar dust exosphere.

LADEE↗
DOE OSTI2021

Magnetopause Reconnection and Indents Induced by Foreshock Turbulence

Abstract Based on global hybrid simulation results, we predict that foreshock turbulence can reach the magnetopause and lead to reconnection as well as Earth‐sized indents. Both the interplanetary magnetic field (IMF) and solar wind are constant in our simulation, and hence, all dynamics are generated by foreshock instabilities. The IMF in the simulation is mostly Sun‐Earth aligned with a weak northward and zero dawn‐dusk component, such that subsolar magnetopause reconnection is not expected without foreshock turbulence modifying the magnetosheath fields. We show a reconnection example to illustrate that the turbulence can create large magnetic shear angles across the magnetopause to induce local bursty reconnection. Magnetopause reconnection and indents developed from the impact of foreshock turbulence can potentially contribute to dayside loss of planetary plasmas.

58 GEOSCIENCES↗
NASA NTRS1974

NBODY - a multipurpose trajectory optimization computer program

Documentation of the NBODY trajectory optimization program is presented in the form of a mathematical development plus a user's manual. Optimal multistage-launch ascent trajectories may be determined by variational thrust steering during the upper phase. Optimal low-thrust interplanetary spacecraft trajectories may also be calculated with solar power or constant power, all-propulsion or embedded coast arcs, fixed or optimal thrust angles, and a variety of terminal end conditions. A hybrid iteration scheme solves the boundary-value problem, while either transversality conditions or a univariate search scheme optimize vehicle or trajectory parameters.

Strack, W. C.↗
NASA NTRS1980

An observed annual cycle in tropical upper stratospheric and mesospheric ozone

Analysis of more than one year of backscattered ultraviolet radiances obtained from an equatorial orbit by the Atmosphere Explorer-E satellite reveals an annual cycle in tropical, high altitude ozone which shows no latitude dependence between 20 degrees south and 20 degrees north. The amplitude of the variation increases with altitude. In the 35 to 45 km altitude region statistics of the data suggest no variation whatsoever, while in the lower mesosphere the radiances indicate an ozone increase of 25 to 30 percent between January and July with a decrease thereafter provided the solar irradiance remained constant except for the variation with earth-sun distance.

Frederick, J. E.↗
NASA NTRS1982

Photovoltaic array: Power conditioner interface characteristics

The electrical output (power, current, and voltage) of flat plate solar arrays changes constantly, due primarily to changes in cell temperature and irradiance level. As a result, array loads such as dc-to-ac power conditioners must be capable of accommodating widely varying input levels while maintaining operation at or near the maximum power point of the array. The array operating characteristics and extreme output limits necessary for the systematic design of array load interfaces under a wide variety of climatic conditions are studied. A number of interface parameters are examined, including optimum operating voltage, voltage energy, maximum power and current limits, and maximum open circuit voltage. The effect of array degradation and I-V curve fill factor or the array power conditioner interface is also discussed. Results are presented as normalized ratios of power conditioner parameters to array parameters, making the results universally applicable to a wide variety of system sizes, sites, and operating modes.

Gonzalez, C. C.↗
NASA NTRS2016

Observations of Space Weather and Space Climate Over the Past 15 Years From SABER (And Longer!)

The global infrared (IR) energy budget of the thermosphere has been reconstructed back 70 years (to 1947). IR cooling, integrated over a solar cycle, is relatively constant over the 5 complete cycles (19 -23) studied. Result implies that solar energy (particles and photons) has similar, small (< 7%) variation from one cycle to next. From Earth's upper atmosphere perspective, solar cycles are really more similar than different, over their length. No consistent relationship between peak of IR cooling and sunspot number peak. Results submitted to GRL 8/2016.

Mlynczak, Marty↗
NASA NTRS1993

Energy balance in the solar transition region. III - Helium emission in hydrostatic, constant-abundance models with diffusion

In our previous papers we described the mathematical formalism and the computed results for energy-balance hydrostatic models of the solar transition region. In this paper we discuss in some detail the limitations of the hydrostatic and one-dimensional assumptions used. Then we analyze the determination of helium emission when diffusion is included. We use transport coefficients estimated from kinetic theory to determine the helium departures from local ionization balance. We calculate the helium spectra for each of our models and evaluate the role of helium in the energy transport. Also, we investigate the effects of coronal illumination on the structure of the transition region and upper chromosphere, and show how coronal illumination affects various EUV lines and the He I 10830 A line. Comparing with both absolute intensities and detailed line profiles, we show that our models are consistent not only with the observed hydrogen spectra but also with the available helium spectra.

Fontenla, J. M.↗
NASA NTRS1980

Cosmological variation of G and the solar luminosity

Teller's analysis of the effects of a varying gravitational constant G on the past solar luminosity is reexamined. It is shown that if Newtonian gravitation is viewed as a nonrelativistic limit of Einstein's theory, there exists (1) a constraint between G and the total mass M of the sun and (2) a change in the radiative energy density-temperature relation, which were not included in Teller's analysis and which change his result from L is about G to the 7th power (found to be unacceptable) to L is about constant, independently of how G might vary with time.

Canuto, V.↗
NASA NTRS2004

Solar Cell Calibration and Measurement Techniques

The increasing complexity of space solar cells and the increasing international markets for both cells and arrays has resulted in workshops jointly sponsored by NASDA, ESA and NASA. These workshops are designed to obtain international agreement on standardized values for the AMO spectrum and constant, recommend laboratory measurement practices and establish a set of protocols for international comparison of laboratory measurements. A working draft of an ISO standard, WD15387, "Requirements for Measurement and Calibration Procedures for Space Solar Cells" was discussed with a focus on the scope of the document, a definition of primary standard cell, and required error analysis for all measurement techniques. Working groups addressed the issues of Air Mass Zero (AMO) solar constant and spectrum, laboratory measurement techniques, and te international round robin methodology. A summary is presented of the current state of each area and the formulation of the ISO document.

Bailey, Sheila↗
NASA NTRS1997

Solar Cell Calibration and Measurement Techniques

The increasing complexity of space solar cells and the increasing international markets for both cells and arrays has resulted in workshops jointly sponsored by NASDA, ESA and NASA. These workshops are designed to obtain international agreement on standardized values for the AMO spectrum and constant, recommend laboratory measurement practices and establish a set of protocols for international comparison of laboratory measurements. A working draft of an ISO standard, WDI 5387, 'Requirements for Measurement and Calibration Procedures for Space Solar Cells' was discussed with a focus on the scope of the document, a definition of primary standard cell, and required error analysis for all measurement techniques. Working groups addressed the issues of Air Mass Zero (AMO) solar constant and spectrum, laboratory measurement techniques, and the international round robin methodology. A summary is presented of the current state of each area and the formulation of the ISO document.

Bailey, Sheila↗
NASA NTRS1980

Rare gases in the past and present solar wind

The elemental abundances, fluxes and isotopic compositions of rare gases in the past and present-day solar wind are discussed on the basis of direct measurements and fossil evidence in lunar and meteorite samples. Spacecraft measurements of the abundances of He, O, Si, Fe, Ne, and Ar with respect to H in the solar wind are shown to agree with relative abundance measurements of these elements in the solar photosphere and corona, while the lack of evidence of systematic depletion with increasing ionic mass suggests solar abundances of the much less abundant Kr and Xe in the solar wind. Relative He, Ne and Ar abundances in the ancient solar wind as derived from lunar ilmenite and the Pesyanoe meteorite are similar to present-day values, except for a factor of two underabundance of He, while the heavy rare gases appear to be enriched by up to a factor of five. The isotopic compositions of solar wind Ar, Kr and Xe have apparently been fairly constant over most of the solar lifetime, whereas He and possibly Ne show evidence of an increasing abundance of their heavy isotopes with increasing solar wind age.

Pepin, R. O.↗
NASA NTRS1985

Diurnal variation of galactic cosmic ray intensity on quiet days

A detailed study of the diurnal variation on long term basis was performed on geomagnetically quiet days using the experimental data of the cosmic ray intensity from the worldwide neutron monitoring stations. During the period when the polarity of the solar magnetic field in the Northern Hemisphere of the sun is negative the phase and amplitude of the diurnal anisotropy on quiet days was observed to remain almost constant. When the polarity of solar magnetic field in the Northern Hemisphere changes from negative to positive, a shift in the phase of the diurnal anisotropy on quiet days towards earlier hours is observed and the shift is found to be maximum during minimum solar activity periods 1953-54 and 1975-76. When the polarity of solar magnetic field changes from positive to negative in the Northern Hemisphere of the Sun the phase of the diurnal anisotropy on quiet days recovers to its usual direction of corotational anisotropy and is observed to remain almost constant till the polarity of the solar magnetic field does not change.

Kumar, S.↗
NASA NTRS2011

The Character of the Solar Wind, Surface Interactions, and Water

We discuss the key characteristics of the proton-rich solar wind and describe how it may interact with the lunar surface. We suggest that solar wind can be both a source and loss of water/OH related volatiles, and review models showing both possibilities. Energy from the Sun in the form of radiation and solar wind plasma are in constant interaction with the lunar surface. As such, there is a solar-lunar energy connection, where solar energy and matter are continually bombarding the lunar surface, acting at the largest scale to erode the surface at 0.2 Angstroms per year via ion sputtering [1]. Figure 1 illustrates this dynamically Sun-Moon system.

Farrell, William M.↗