Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “solar constant”

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 1,027 records · Page 57
All sourcesNASA NTRSDOE OSTI
NASA NTRS2003

Program for Computing Albedo

Simple Thermal Environment Model (STEM) is a FORTRAN-based computer program that provides engineering estimates of top-of-atmosphere albedo and outgoing long-wave radiation (OLR) for use in analyzing thermal loads on spacecraft near Earth. The thermal environment of a spacecraft is represented in STEM as consisting of direct solar radiation; short-wave radiation reflected by the atmosphere of the Earth, as characterized in terms of the albedo of the Earth; and OLR emitted by the atmosphere of the Earth. STEM can also address effects of heat loads internal to a spacecraft. Novel features of STEM include (1) the use of Earth albedo and OLR information based on time series of measurements by Earth Radiation Budget Experiment satellites in orbit; (2) the ability to address thermal time constants of spacecraft systems by use of albedo and OLR values representing averages over a range of averaging times; and (3) the ability to address effects, on albedo and OLR values, of satellite orbital inclination, the angle between the plane of a spacecraft orbit and the line between the centers of the Earth and Sun, the solar zenith angle, and latitude.

Justus, Carl G.↗
DOE OSTI2022

csphothybv3: A hybrid sky radiance scan scenario version 3 data

This hybrid scan starts at the position of the Sun and first follows the great circle that is orthogonal to the Principal Plane until it reaches a viewing zenith angle of 75 degrees and then follows the almucantar keep that viewing zenith angle constant. The scan is then repeated in the opposite azimuth direction. This mode was designed to optimize the range of scattering angles and significantly improves the retrieval of inversion parameters especially at low solar zenith angles.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1976

On the nonexistence of plane-polarized large amplitude Alfven waves

A theorem is presented which shows that purely Alfvenic plane-polarized large-amplitude disturbances in the solar wind are not possible and will never be observed. The theorem establishes that there is no nontrivial plane-polarized magnetic-field configuration in which the parameter B-squared is constant throughout all space. It is noted, however, that more general nonplanar Alfvenic disturbances may well exist.

Barnes, A.↗
NASA NTRS1978

Proton collisional excitation in the ground configuration of Fe/11+/

Proton collisional excitation cross sections at solar coronal energies for the Fe(11+) /3S(2)3p(3)/ ground-configuration transitions are presented. Semiclassical Coulomb excitation theory is used with direct integration of the resulting Schroedinger equation. The rate constants at coronal temperatures are compared with the corresponding ones for electron impact excitation.

Landman, D. A.↗
NASA NTRS1980

On the cause of plasma-sheet thinning during magnetospheric substorms

It is proposed that the thinning of the plasma sheet during magnetospheric substorms is caused by an earthward gradient of the rate of magnetic merging (field annihilation) in the tail current sheet, which is in turn caused by the velocity-dependent access of plasma mantle particles to the current sheet. A simple model calculation based on this effect predicts a thinning time constant of the order of 1 hour, consistent with observations. The mechanism is also consistent with the observed correlation between plasma-sheet thinning and southward-directed magnetic field components in the solar wind.

Hill, T. W.↗
NASA NTRS1985

Jet production in super-Eddington accretion disks

A two-dimensional, radiation-coupled, Newtonian hydrodynamic simulation is reported for a super-Eddington, mass accretion rate, M = 4 M(E) disk accretion flow onto a 3-solar mass pseudoblack hole. Near the disk midplane, convection cells effectively block the accretion flow, even though viscous heating maximizes there. Accretion predominantly occurs in a supersonic inflow which follows streamlines of approximately constant angular momentum. The optically thick inflow traps radiation so that 80 percent of the luminosity is absorbed by the black hole; the emergent power is sub-Eddington. An axial jet self consistently forms just outside a conical photosphere which bounds the accretion zone; radiation pressure accelerates the jet to about 10 to the 10th cm/s. The jet's mass efflux is only 0.4 percent of the total mass accretion rate.

Eggum, G. E.↗
NASA NTRS1985

Inhibition of conductive heat flow by magnetic constriction in the corona and transition region - Dependence on the shape of the constriction

Attention is given to the process by which the shape of the constriction of field lines inhibiting the conduction of heat down from the corona acts in conjunction with the degree of constriction to inhibit the heat flow. The analytical model for the heat flow involves tapered flux tubes in which the plasma properties are constant on cross sections, while the plasma is static and the only energy transfer is by thermal conduction. It is determined that only two specific solutions to the model are applicable to the solar atmosphere: the steady state, which is appropriate for quiet regions and for active ones that are not flaring, and the time-dependent case, in which no heat enters the hot end, which is appropriate for conductive cooling of flare loops.

Moore, R. L.↗
NASA NTRS1992

Time variation of the meteoritic contribution to the atmosphere of Mars

The meteoritic contribution to the planets of the inner solar system varies significantly with time. During the first billion years, the flux of meteoritic material was significantly greater than present. Over the past 3.6 billion years, the background flux has been relatively constant, but shorter periods of significantly enhanced flux are associated with discrete events such as major impacts of large bodies onto the planets or their moons and passage through cometary debris streams. The topics covered include the following (1) the last 3.6 billion years; (2) large impacts; (3) passage through comet tail; and (4) major collision in the main-belt.

Flynn, G. J.↗
NASA NTRS1991

Metal opacities and convective core overshooting in Population I stars

New stellar opacities computed by Rogers and Iglesias are found to lead to revised evolutionary models for stars of intermediate-to-high mass that show remarkably close agreement with observed stars, under otherwise standard physical assumptions. Most or all of the earlier discrepancies, except for the problem of predicted apsidal motion constants that are perhaps still too large, appear to have been resolved by using these new opacities with their increased metal line contribution. Thus, the implied interior metallicity of massive stars in the solar neighborhood now becomes 'normal'. Furthermore, the effective distance of convective overshooting beyond the classical convective core boundary is confirmed to be small and probably less than 0.2 times the local pressure scale height.

Stothers, Richard B.↗
NASA NTRS1993

Interferometric observations of non-maser SiO emission from circumstellar envelopes of AGB stars - Acceleration regions and SiO depletion

High- and medium-resolution images of SiO J = 2-1(V = 0) from the circumstellar envelopes (CSEs) of three oxygen-rich stars, Chi Cyg, RX Boo, and IK Tau, were obtained. The SIO images were found to be roughly circular, implying that the CSEs are spherically symmetric on angular-size scales of about 3-9 arcsec. The observed angular half-maximum intensity source radius is nearly independent of the LSR velocity for all three CSEs. Chi Cyg and RX Boo are argued to be less than 450 pc distant, and have mass-loss rates larger than about 10 exp -6 solar mass/yr. In Chi Cyg and RX Boo, the line profiles at the peak of the brightness distribution are rounded, typical of optically-thick emission from a spherical envelope expanding with a constant velocity. In the IK Tau line profiles, an additional narrower central component is present, probably a result of emission from an inner circumstellar shell with a significantly smaller expansion velocity than the extended envelope.

Sahai, Raghvendra↗
NASA NTRS1995

Driven acoustic oscillations within a vertical magnetic field

The effects of a vertical magnetic field on p-mode frequencies, line widths, and eigenfunctions, are examined. A solar model, consisting of a neutrally stable polytropic interior matched to an isothermal chromosphere, is applied. The p-modes are produced by a spatially distributed driver. The atmosphere is threaded by a constant vertical magnetic field. The frequency shifts due to the vertical magnetic field are found to be much smaller than the shifts caused by horizontal fields of similar strength. A large vertical field of 2000 G produces shifts of several nHz. It is found that the frequency shifts decrease with increasing frequency and increase with field strength. The coupling of the acoustic fast mode to the escaping slow modes is inefficient. Constant vertical magnetic field models are therefore incapable of explaining the high level of absorption observed in sunspots and plage.

Hindman, Bradley W.↗
NASA NTRS2022

Spectroscopic Study of Solar Transition Region Oscillations in the Quiet-Sun Observed By IRIS Using the Si IV Spectral Line

In this paper, we use the Si IV 1393.755 Å spectral line observed by the Interface Region Imaging Spectrograph (IRIS) in the quiet-Sun (QS) to determine the physical nature of the solar transition region (TR) oscillations. We analyse the properties of these oscillations using wavelet tools (e.g. power, cross-power, coherence, and phase difference) along with the stringent noise model (i.e. power law + constant). We estimate the period of the intensity and Doppler velocity oscillations at each chosen location in the QS and quantify the distribution of the statistically significant power and associated periods in one bright region and two dark regions. In the bright TR region, the mean periods in intensity and velocity are 7 min and 8 min, respectively. In the dark regions, the mean periods in intensity and velocity are 7 min and 5.4 min, respectively. We also estimate the phase difference between the intensity and Doppler velocity oscillations at each location. The statistical distribution of the phase difference is estimated, which peaks at −119° ± 13°, 33° ± 10°, 102° ± 10° in the bright region and at −153° ± 13°, 6° ± 20°, 151° ± 10° in the dark regions. The statistical distribution reveals that the oscillations are caused by propagating slow magneto-acoustic waves encountered with the TR. Some of these locations may also be associated with standing slow waves. Moreover, in the given time domain, several locations exhibit the presence of both propagating and standing oscillations at different frequencies.

MHD – Sun: oscillations↗
DOE OSTI2021

Light-activated interlayer contraction in two-dimensional perovskites for high-efficiency solar cells

Understanding and tailoring the physical behaviour of halide perovskites under practical environments is critical for designing efficient and durable optoelectronic devices. Here, we report that continuous light illumination leads to >1% contraction in the out-of-plane direction in two-dimensional hybrid perovskites, which is reversible and strongly dependent on the specific superlattice packing. X-ray photoelectron spectroscopy measurements show that constant light illumination results in the accumulation of positive charges in the terminal iodine atoms, thereby enhancing the bonding character of inter-slab I–I interactions across the organic barrier and activating out-of-plane contraction. Correlated charge transport, structural and photovoltaic measurements confirm that the onset of the light-induced contraction is synchronized to a threefold increase in carrier mobility and conductivity, which is consistent with an increase in the electronic band dispersion predicted by first-principles calculations. Flux-dependent space-charge-limited current measurement reveals that light-induced interlayer contraction activates interlayer charge transport. Lastly, the enhanced charge transport boosts the photovoltaic efficiency of two-dimensional perovskite solar cells up to 18.3% by increasing the device’s fill factor and open-circuit voltage.

36 MATERIALS SCIENCE↗
NASA NTRS1995

Radiation Pressure, Poynting-Robertson Drag, and Solar Wind Drag in the Restricted Three-Body Problem

In this paper, we examine the effects of radiation pressure, Poynting-Robertson (PR) drag, and solar wind drag on dust grains trapped in mean motion resonances with the Sun and Jupiter in the restricted (negligible dust mass) three-body Problem. We especially examine the evolution of dust grains in the 1:1 resonance. As a first step, the Sun and Jupiter are idealized to both be in circular orbit about a common center of mass (circular restricted three-body problem). From the equation of motion of the dust particle in the rotating reference frame, the drag-induced time rate of change of its Jacobi "constant," C, is then derived and expressed in spherical coordinates. This new mathematical expression in spherical coordinates shows that C, in the 1:1 resonance, both oscillates and secularly increases with increasing time. The new expression gives rise to an easy understanding of how an orbit evolves when the radiation force and solar wind drag are included. All dust grain orbits are unstable in time when PR and solar wind drag are included in the Sun-Jupiter-dust system. Tadpole orbits evolve into horseshoe orbits; and these orbits continuously expand in size to lead to close encounters with Jupiter. Permanent trapping is impossible. Orbital evolutions of a dust grain trapped in the 1:1 resonance in the planar circular, an inclined case, an eccentric case, and the actual Sun-Jupiter case are numerically simulated and compared with each other and show grossly similar time behavior. Resonances other than 1:1 are also explored with the new expression. Stable exterior resonance trapping may be possible under certain conditions. One necessary condition for such a trap is derived. Trapping in interior resonances is shown to be always unstable.

Liou, Jer-Chyi↗
NASA NTRS2020

A Study of a Magnetic Cloud Propagating through Large-Amplitude Alfvén Waves

We discuss Wind observations of a long and slow magnetic cloud (MC) propagating through large-amplitude Alfvén waves (LAAWs). The MC axis has a strong component along GSE X, as also confirmed by a Grad-Shafranov reconstruction. It is overtaking the solar wind at a speed roughly equal to the upstream Alfvén speed, leading to a weak shock wave âLij17 hrs. ahead. We give evidence to show that the nominal sheath region is populated by LAAWs: (i) a well-defined deHoffman-Teller frame in which there is excellent correlation between the field and flow vectors, (ii) constant field and total pressure, and (iii) an Alfvén ratio (i.e. ratio of kinetic-to-magnetic energy of the fluctuations) near unity at frequencies much lower than the ion cyclotron frequency in the spacecraft frame. In the region where the LAAWs approach the MCâAZs front boundary there are field and flow discontinuities. At the first, magnetic reconnection is taking place, as deduced from a stress balance test (Walen test). This severs connection of some field lines to the Sun and the solar wind strahl disappears. There follows a aLij2-hour interval where the magnetic field strength is diminished while pressure balance is maintained. Here the bi-directionality of the suprathermal electron flows is intermittently disrupted. This interval ends with a slow expansion fan downstream of which there is a dropout of halo electrons just inside the front boundary of the MC. This study illustrates an untypical case of a slow MC interacting with LAWWs in the slow solar wind.

C. J. Farrugia↗
NASA NTRS2004

Elemental Abundance Variations Observed in Solar Energetic Particle Events During Solar Cycle 23

We report on observations of the abundances of elements from Helium to Nickel in over 50 different solar energetic particle events using the Solar Isotope Spectrometer (SIS) on-board the Advanced Composition Explorer (ACE) spacecraft. It had originally been expected that the energy spectra of different elements would show spectral roll-overs at energies related to the Q/M ratio of each element. Due to the partial stripping of Fe and essentially complete stripping of O, it was expected that the Fe/O ratio would be observed to decrease with increasing energy. While many events show this pattern, others have Fe/O which is constant with energy, while for yet others Fe/O actually increases with energy. Events having constant Fe/O could simply have their spectral breaks outside of the observed energy range. However, events which show increasing Fe/O cannot be explained within the framework of spectral breaks. Possible explanations include injection of remnant heavy ions from earlier impulsive events, hybrid Events consisting of a combination of flare-accelerated and shock-accelerated particles from a single solar event, and some new physical process in shock acceleration. We will report on efforts to distinguish these possible explanations.

vonRosenvinge, T. T.↗
NASA NTRS1988

Observations of energetic oxygen and carbon ions with charge states between 3 and 6 in the magnetosphere

Data obtained by the AMPTE/CCE charge-energy-mass spectrometer are used to study the average spatial distributions of oxygen and carbon ions with charge states between 3 and 6. The O(6+) and C(6+) ion fluxes are found to increase with the drift shell parameter L up to a constant level at L of not less than 7. It is suggested that the diurnal variations noted are related to the shape of the L profiles. The results support a model in which the solar wind origin O(6+) and C(6+) ions and the terrestrial origin O(+) and O(2+) ions are transported from the tail towards the earth. Charge exchange processes near the earth produce the oxygen and carbon ions with charge states between 3 and 5.

Kremser, G.↗