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NASA NTRS1985

Submillimeter observations of evolved stars

Broadband submillimeter observations of thermal emission from several evolved stars have been obtained using the United Kingdom Infrared Telescope on Mauna Kea, Hawaii. The observations were carried out at an effective wavelength of 400 microns in order to estimate the mass loss rates in dust from the stars. Direct estimates of mass loss rates are in the range 10 to the -9th to 10 to the -6th solar mass/yr. Analysis of the spectrum of IRC + 10216 confirmed previous estimates of dust grain emissivity in the range 10-1000 microns. The infrared properties of IRC + 10216 are found to be similar to the carbon rich object CRL 3068. No systematic difference was found between the dust masses of carbon rich and oxygen rich envelopes. The largest mass loss rates in dust were obtained for the bipolar objects OH 231.8 + 4.2 CRL 2688, CRL 618, and NGC 7027. It is suggested that the ratios of gas to dust, and the slopes of the far infrared to submillimeter wavelength continua of these stars objects are probably representative of amorphous rather than crystalline grains.

Sopka, R. J.↗

NASA NTRS1985

MHD analysis of the evolution of solar magnetic fields and currents in an active region

A self-consistent, newly developed, nonplanar MHD model is used to investigate the evolution of field and current structures in solar active regions due to photospheric shearing motions. It is demonstrated that this model can predict physical parameters that may help improve understanding of the evolution of those field and current structures. Numerical results on the magnetic energy intensity, electric current intensity, and magnetic field configuration are presented.

Wu, S. T.↗

NASA NTRS1986

Study of Travelling Interplanetary Phenomena (STIP) workshop travel

Thirty six abstracts are provided from the SCOSTEP/STIP Symposium on Retrospective Analyses and Future Coordinated Intervals held in Switzerland on June 10 to 12, 1985. Six American scientists participated in the symposium and their abstracts are also included. The titles of their papers are: (1) An analysis of near surface and coronal activity during STIP interval 12, by T. E. Gergely; (2) Helios images of STIP intervals 6, B. V. Jackson; (3) Results from the analysis of solar and interplanetary observations during STIP interval 7, S. R. Kane; (4) STIP interval 19, E. Cliver; (5) Hydrodynamic buoyancy force in the solar atmosphere, T. Yeh; and (6) A combined MHD modes for the energy and momentum transport from solar surface to interplanetary space, S. T. Wu.

Wu, S. T.↗

NASA NTRS1986

The response function of modulated grid Faraday cup plasma instruments

Modulated grid Faraday cup plasma analyzers are a very useful tool for making in situ measurements of space plasmas. One of their great attributes is that their simplicity permits their angular response function to be calculated theoretically. An expression is derived for this response function by computing the trajectories of the charged particles inside the cup. The Voyager Plasma Science (PLS) experiment is used as a specific example. Two approximations to the rigorous response function useful for data analysis are discussed. The theoretical formulas were tested by multi-sensor analysis of solar wind data. The tests indicate that the formulas represent the true cup response function for all angles of incidence with a maximum error of only a few percent.

Barnett, A.↗

NASA NTRS1986

Electron density diagnostics in the 10-100 A interval for a solar flare

Electron density measurements from spectral-line diagnostics are reported for a solar flare on July 13, 1982, 1627 UT. The spectrogram, covering the 10-95 A interval, contained usable lines of helium-like ions C V, N VI, O VII, and Ne IX which are formed over the temperature interval 0.7-3.5 x 10 to the 6th K. In addition, spectral-line ratios of Si IX, Fe XIV, and Ca XV were compared with new theoretical estimates of their electron density sensitivity to obtain additional electron density diagnostics. An electron density of 3 x 10 to the 10th/cu cm was obtained. The comparison of these results from helium-like and other ions gives confidence in the utility of these tools for solar coronal analysis and will lead to a fuller understanding of the phenomena observed in this flare.

Brown, W. A.↗

NASA NTRS1986

Response function of modulated grid Faraday cup plasma instruments

Modulated grid Faraday cup plasma analyzers are a very useful tool for making in situ measurements of space plasmas. One of their great attributes is that their simplicity permits their angular response function to be calculated theoretically. An expression is derived for this response function by computing the trajectories of the charged particles inside the cup. The Voyager plasma science experiment is used as a specific example. Two approximations to the rigorous response function useful for data analysis are discussed. Multisensor analysis of solar wind data indicates that the formulas represent the true cup response function for all angles of incidence with a maximum error of only a few percent.

Barnett, A.↗

NASA NTRS1985

Sensitivity analysis of low bulk resistivity solar cells

In an effort to identify critical parameters of single-junction solar cells and to determine their relative sensitivity, parametric analyses have been conducted with a computer code SPCOLAY. A receipt for high-efficiency cells emerges from the analyses that requires the primary ingredients of low bulk resistivity (0.1-0.2 ohm-cm), a bulk diffusion length as large as attainable (greater than 100 microns), and a small front surface recombination velocity (about 100 cm/sec). Other parameters appear to play less sensitive roles.

Lin, E. I. H.↗

NASA NTRS1988

Thermal distortion analysis of the space station solar dynamic concentrator

A method was developed to evaluate the thermal distortion of the Space Station Solar Dynamic Concentrator and the effects of thermal distortion on concentrator optical performance. The analytical method includes generating temperature distributions with TRASYS and SINDA models, interfacing the SINDA results with the SINDA-NASTRAN Interface Program (SNIP), calculating thermal distortion with a NASTRAN/PATRAN finite element model, and providing flux distribution maps within the receiver with the ray tracing OFFSET program. Temperature distributions, thermally induced slope errors, and flux distribution maps within the receiver are discussed. Results during a typical orbit indicate that temperatures of the hexagonal panels and triangular facets range between -18 and 99 C (-1 to 210 F), facet rotations are less than 0.2 mrad, and a change in facet radius due to thermal flattening is less than 5 percent. The predicted power loss with thermal distortion effects was less than 0.3 percent. The thermal distortion of the Solar Dynamic concentrator has negligible effect on the flux distribution within the receiver cavity.

Trudell, Jeffrey J.↗

NASA NTRS1989

Analysis of Nd3+:glass, solar-pumped, high-powr laser systems

The operating characteristics of Nd(3+):glass lasers energized by a solar concentrator were analyzed for the hosts YAG, silicate glass, and phosphate glass. The modeling is based on the slab zigzag laser geometry and assumes that chemical hardening methods for glass are successful in increasing glass hardness by a factor of 4. On this basis, it was found that a realistic 1-MW solar-pumped laser might be constructed from phosphate glass 4 sq m in area and 2 mm thick. If YAG were the host medium, a 1-MW solar-pumped laser need only be 0.5 sq m in area and 0.5 cm thick, which is already possible. In addition, Nd(3+) doped glass fibers were found to be excellent solar-pumped laser candidates. The small diameter of fibers eliminates thermal stress problems, and if their diameter is kept small (10 microns), they propagate a Gaussian single mode which can be expanded and transmitted long distances in space. Fiber lasers could then be used for communications in space or could be bundled and the individual beams summed or phase-matched for high-power operation.

Zapata, L. E.↗

NASA NTRS1988

Thermal distortion analysis of the Space Station solar dynamic concentrator

Trudell, Jeffery J.↗

NASA NTRS1990

Evidence for a supermassive black hole in the nucleus of the Seyfert galaxy NGC 5548

The international campaign to monitor the variable Seyfert 1 galaxy NGC 5548 with the IUE has provided an extensive and well-sampled set of spectroscopic observations. These observations are used to study the response of the C IV 1550 A emission-line profile to changes in the photoionizing continuum. Near the end of the IUE campaign, the continuum flux at 1440 A and the total C IV flux dopped by factors of 2.9 and 1.8, respectively, in 16 days. The red wing of the C IV profile responded more rapidly to the sharp continuum drop than the blue wing, indicating that clouds in the inner broad-line region (BLR) are undergoing gravitational infall. These results provide direct evidence that the central engine is a supermassive object, presumably a black hole, with a mass on the order of 10 to the 7th solar masses. Analysis of the profile variations also demonstrates that excess emission in the blue wing of C IV is from a component that is physically distinct from the bulk of the BLR.

Crenshaw, D. Michael↗

NASA NTRS1992

Description, analysis and impact of major solar activity during recent U.S. Shuttle missions

Since STS-26, three large solar events have occurred during Shuttle missions: a geomagnetic storm during STS-29 and solar particle events (SPEs) during STS-28 and -34. The maximum dose to a crew attributed to an SPE was estimated to be 30 micro-Gy. Time-resolved dosimetry measurements of the SPE dose during STS-28 were made using the USAF Radiation Monitoring Equipment. Comparison of calculated and measured dose demonstrated a discrepancy, possibly a result of deficiencies in the geomagnetic cutoff model used. This experience demonstrates that dose from an SPE is strongly dependent on numerous factors such as orbit inclination, SPE start time, spectral parameters and geomagnetic field conditions; the exact combination of these factors is fortuitous. New sources of data and procedures are being investigated, including real-time tracking of auroral oval positions or determination of particle cutoff latitudes, for incorporation into operational Shuttle radiation support practices.

Golightly, M. J.↗

NASA NTRS1991

Solar flare protection for manned lunar missions - Analysis of the October 1989 proton flare event

Several large solar proton events occurred in the latter half of 1989. For a moderately shielded spacecraft in free space, the potential exposure would have been greatest for the flare which occurred between October 19 to 27, 1989. The temporal variations of the proton energy spectra at approximately 1 AU were monitored by the GOES-7 satellite. These data, recorded and processed at the NOAA-Boulder Space Environment Laboratory, provide the opportunity to analyze dose rates and cumulative doses which might be incurred by astronaus in transit to, or on, the moon. Of particular importance in such an event is the time development of exposure in the early phases of the flare, for which dose rates may range over many orders of magnitude in the first few hours. The cumulative dose as a function of time for the entire event is also predicted. In addition to basic shield calculations, dose rate contours are constructed for flare shelters in free-space and on the lunar surface.

Simonsen, Lisa C.↗

NASA NTRS1992

The Galileo and Pioneer Venus ultraviolet spectrometer experiments - Solar Lyman-alpha latitude variation at solar maximum from interplanetary Lyman-alpha observations

Solar Ly-alpha latitude variation at solar maximum is examined on the basis of interplanetary Ly-alpha observations made during the Galileo and Pioneer Venus UV spectrometer experiments. A comparison is made of the latitude variation of the interplanetary (IP) Ly-alpha signal in 1986 at solar minimum from Pioneer Venus and in 1990 at solar maximum from Galileo. The Galileo EUV spectrometer shows that a large enhancement of the IP Ly-alpha emission occurred over the intervening four years near the solar equator. An IP Ly-alpha model is developed which considers the latitude variation of the solar Ly-alpha flux. The model fit to the data shows a 25-percent decrease of the full disk solar Ly-alpha flux from solar equator to solar pole in 1990. A detailed study of the Galileo IP Ly-alpha observations on day-of-year 190, 193, 197, and 200 in 1990 reveals that large variations occur in response to the 27-d solar variation. Analysis of these data shows that a maximum variation of 20 percent can be expected in the IP Ly-alpha upwind intensity over this 27-d period.

Pryor, W. R.↗

NASA NTRS1994

Temperature minima in the average thermal structure of the middle mesosphere (70 - 80 km) from analysis of 40- to 92-km SME global temperature profiles

Global temperatures have been derived for the upper stratosphere and mesosphere from analysis of Solar Mesosphere Explorer (SME) limb radiance profiles. The SME temperature represent fixed local time observations at 1400 - 1500 LT, with partial zonal coverage of 3 - 5 longitudes per day over the 1982-1986 period. These new SME temperatures are compared to the COSPAR International Ionosphere Reference Atmosphere 86 (CIRA 86) climatology (Fleming et al., 1990) as well as stratospheric and mesospheric sounder (SAMS); Barnett and Corney, 1984), National Meteorological Center (NMC); (Gelman et al., 1986), and individual lidar and rocket observations. Significant areas of disagreement between the SME and CIRA 86 mesospheric temperatures are 10 K warmer SME temperatures at altitudes above 80 km. The 1981-1982 SAMS temperatures are in much closer agreement with the SME temperatures between 40 and 75 km. Although much of the SME-CIRA 86 disagreement probably stems from the poor vertical resolution of the observations comprising the CIRA 86 modelm, some portion of the differences may reflect 5- to 10-year temporal variations in mesospheric temperatures. The CIRA 86 climatology is based on 1973-1978 measurements. Relatively large (1 K/yr) 5- to 10-year trends in temperatures as functions of longitude, latitude, and altitude have been observed for both the upper stratosphere (Clancy and Rusch, 1989a) and mesosphere (Clancy and Rusch, 1989b; Hauchecorne et al., 1991). The SME temperatures also exhibit enhanced amplitudes for the semiannual oscillation (SAO) of upper mesospheric temperatures at low latitudes, which are not evident in the CIRA 86 climatology. The so-called mesospheric `temperature inversions' at wintertime midlatitudes, which have been observed by ground-based lidar (Hauschecorne et al., 1987) and rocket in situ measurements (Schmidlin, 1976), are shown to be a climatological aspect of the mesosphere, based on the SME observations.

Clancy, R. Todd↗

NASA NTRS1999

Transient Thermal Analysis of a Refractive Secondary Solar Concentrator

A secondary concentrator is an optical device that accepts solar energy from a primary concentrator and further intensifies and directs the solar flux. The refractive secondary is one such device; fabricated from an optically clear solid material that can efficiently transmit the solar energy by way of refraction and total internal reflection. When combined with a large state-of-the-art rigid or inflatable primary concentrator, the refractive secondary enables solar concentration ratios of 10,000 to 1. In support of potential space solar thermal power and propulsion applications, the NASA Glenn Research Center is developing a single-crystal refractive secondary concentrator for use at temperatures exceeding 2000K. Candidate optically clear single-crystal materials like sapphire and zirconia are being evaluated for this application. To support this evaluation, a three-dimensional transient thermal model of a refractive secondary concentrator in a typical solar thermal propulsion application was developed. This paper describes the model and presents thermal predictions for both sapphire and zirconia prototypes. These predictions are then used to establish parameters for analyzing and testing the materials for their ability to survive thermal shock and stress.

Geng, Steven M.↗

NASA NTRS2000

Final Report for Isee/3ICE Data Restoration NAG5-7188 Restoration of ISEE-3/ICE X-Ray Data

The objective of this project is to take solar flare X-ray data obtained by ISEE-3/ICE (Third International Sun Earth Explorer/ International Cometary Explorer) spacecraft and convert it from its current non-standard format into FITS binary tables. These files will then be made available to the public at the Solar Data Analysis Center (SDAC).

Fisher, George H.↗

NASA NTRS2001

A Time-Frequency Analysis of the Effects of Solar Activities on Tropospheric Thermodynamics

Whether the Sun has significantly influenced the climate during the last century has been under extensive debates for almost two decades. Since the solar irradiance varies very little in a solar cycle, it is puzzling that some geophysical parameters show proportionally large variations which appear to be responding to the solar cycles. For example, variation in low altitude clouds is shown correlated with solar cycle, and the onset of Forbush decrease is shown correlated with the reduction of the vorticity area index. A possible sun-climate connection is that galactic cosmic rays modulated by solar activities influence cloud formation. In this paper, we apply wavelet transform to satellite and surface data to examine this hypothesis. Data analyzed include the time series for solar irradiance, sunspots, UV index, temperature, cloud coverage, and neutron counter measurements. The interactions among the elements in the Earth System under the external and internal forcings give out very complex signals.The periodicity of the forcings or signals could range widely. Since wavelet transforms can analyze multi-scale phenomena that are both localized in frequency and time, it is a very useful technique for detecting, understanding and monitoring climate changes.

Kiang, Richard K.↗