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Results for “Solar Irradiance”

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 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

The solar irradiance from 200 to 330 nm

The full disk solar spectrum over the wavelength range 200-330 nm is measured with a spectral resolution of 0.12 nm. The measurement is performed by using a double monochromator pointed at the sun from a high altitude parachute. Only small corrections are required to account for atmospheric absorption. Good agreement is obtained with previously reported measurements.

Mentall, J. E.↗
NASA NTRS2014

Dependence of Lunar Surface Charging on Solar Wind Plasma Conditions and Solar Irradiation

The surface of the Moon is electrically charged by exposure to solar radiation on its dayside, as well as by the continuous flux of charged particles from the various plasma environments that surround it. An electric potential develops between the lunar surface and ambient plasma, which manifests itself in a near-surface plasma sheath with a scale height of order the Debye length. This study investigates surface charging on the lunar dayside and near-terminator regions in the solar wind, for which the dominant current sources are usually from the pohotoemission of electrons, J(sub p), and the collection of plasma electrons J(sub e) and ions J(sub i). These currents are dependent on the following six parameters: plasma concentration n(sub 0), electron temperature T(sub e), ion temperature T(sub i), bulk flow velocity V, photoemission current at normal incidence J(sub P0), and photo electron temperature T(sub p). Using a numerical model, derived from a set of eleven basic assumptions, the influence of these six parameters on surface charging - characterized by the equilibrium surface potential, Debye length, and surface electric field - is investigated as a function of solar zenith angle. Overall, T(sub e) is the most important parameter, especially near the terminator, while J(sub P0) and T(sub p) dominate over most of the dayside.

Photoemission↗
NASA NTRS1989

Photometric measurements of solar irradiance variations due to sunspots

A photometric telescope constructed to obtain photometric sunspot areas and deficits on a daily basis is described. Data from this Cartesian full disk telescope (CFDT) are analyzed with attention given to the period between June 4 and June 17, 1985 because of the availability of overlapping sunspot area and irradiance deficit data from high-resolution digital spectroheliograms made with the San Fernando Observatory 28 cm vacuum solar telescope and spectroheliograph. The CFDT sunspot deficits suggest a substantial irradiance contribution from faculae and active region plage.

Chapman, G. A.↗
NASA NTRS2021

The Effect of Missing Groups in the Calculation of the Solar Irradiance Deficit: Analysis of the Sunspot Areas from the SOON Network

Sunspot areas are one of the most important indices of solar activity. To obtain an extended time series covering multiple solar cycles one must combine data from different observatories after a proper comparison and calibration of the individual data sets. We compare the daily and group values of sunspot areas provided by the different stations from the Solar Optical Observing Network, SOON, which are determined using similar instruments and techniques. We investigate if there are systematic differences among the stations and whether the differences in the daily values can be attributed to missing groups in the records or errors in the measurements. We find significant differences among the stations of the SOON network in terms of sizes (average daily and group values), quality of observations and coverage (considering number of missing groups and data gaps). Our results indicate that calibration factors for daily values can be used with confidence to combine data sets from different stations. However, for some applications which require the location of the sunspot groups the same correction factors should not be used. We estimate the irradiance deficit due to sunspot through the Photometric Sunspot Index and compare the output from similar data sets to quantify the effect of missing groups. We find differences as high as 150 ppm during the maximum of solar cycle. The effect increases for sunspot groups near the center of the disk accounting for about 80% of the observed differences.

Luis Leuzzi↗
NASA NTRS1983

Solar irradiance variations. II - Analysis of the extreme ultraviolet measurements onboard the Atmosphere Explorer E satellite

Five of the extreme ultraviolet channels (L-alpha, L-beta, He I, He II, Fe XV) measuring irradiance fluctuations on board the AE-E satellite between 1977 and 1980 have been studied in detail. It is shown that the daily variations correspond very closely to the daily variations in solar radio emission (F10.7), but that the UV data are afflicted with serious and to date unrecognized calibration changes during the period of operation of the instruments. In order to correct for these changes, a statistical analysis is carried out, and a set of corrections to the raw data is suggested. The resulting, now uniform, data are then compared with rocket measurements (L-alpha) and data acquired onboard the AE-C satellite (L-beta). Finally the remaining discrepancies are discussed. After concluding that they are below the overall level of uncertainties, a first-order 10-year run of EUV irradiances derived from F10.7 data is proposed. This estimate includes the ratio of irradiance levels between the maxima of solar cycles 20 and 21 and the intervening minimum.

Oster, L.↗
NASA NTRS2019

The SDO/EVE Solar Irradiance Coronal Dimming Index Catalog. I. Methods and Algorithms

When a coronal mass ejection departs, it leaves behind a temporary void. That void is known as coronal dimming, and it contains information about the mass ejection that caused it. Other physical processes can cause parts of the corona to have transient dimmings, but mass ejections are particularly interesting because of their influence in space weather. Prior work has established that dimmings are detectable even in disk-integrated irradiance observations, i.e., Sun-as-a-star measurements. The present work evaluates four years of continuous Solar Dynamics Observatory Extreme Ultraviolet Experiment (EVE) observations to greatly expand the number of dimmings we may detect and characterize, and collects that information into James’s EVE Dimming Index catalog. This paper details the algorithms used to produce the catalog, provides statistics on it, and compares it with prior work. The catalog contains 5051 potential events (rows), which correspond to all robustly detected solar eruptive events in this time period as defined by >C1 flares. Each row has a corresponding 27,349 elements of metadata and parameterizations (columns). In total, this catalog is the result of analyzing 7.6 million solar ultraviolet light curves.

James’s EVE Dimming Index (JEDI)↗
NASA NTRS1985

Data on total and spectral solar irradiance - Reply to comments

The letter is a response to Frohlich's (1983) comments on an earlier paper (Mecherikunnel et al., 1983) containing a brief survey of the available data on the solar constant and its spectral distribution. The sources of the initial data used in the above study are mentioned, and comments are made on the accuracy of the measurements. Reasons are given for using NASA/ASTM data in the computations.

Mecherikunnel, A. T.↗
NASA NTRS1984

Ground-based Measurements of Solar Irradiance Variations

Observations and analysis programs being carried out at the San Fernando Observatory are reviewed. A digital analysis of sunspot areas from full disk photographs shows an especially good correlation with areas published in the Solar Geophysical Data Bulletin with scale factor near unity. Results are presented from photoelectric photometry of active regions using the Extreme Limb Photometer. These results suggest energy balance between sunspots and faculae. Preliminary results are presented from a new program of photoelectric photometry using a linear array of diodes. Results are presented for the August 1982 passage of a large active region. This active region caused a maximum dip in the quiet Sun irradiance of about 800 parts per million.

Chapman, G. A.↗
NASA NTRS1988

In-flight calibration of solar irradiance measurements by direct comparison with stellar observations

The Solstice instrument aboard the upper atmosphere research satellite (UARS) is designed to correct the deficiencies of both long-term instrument drift and of intercomparison of solar data sets taken at different times by different instruments. The Solstice will make repeated measurements, spaced throughout the mission, of a number of bright early-type stars. In addition, it will determine the ratio of the solar flux to the average flux from an ensemble of stars. This ratio will be monitored throughout the UARS mission and archived.

Rottman, Gary J.↗
NASA NTRS1971

Behavior of lithium in irradiated solar cells.

The current state of the art in radiation resistant lithium-doped silicon solar cells is reviewed. Fabrication techniques are reviewed. Characteristics of lithium-doped cells are discussed. Behavior of lithium-doped cells during 1 MeV electron irradiation are studied for various types of cells. Effects of variations in lithium and oxygen concentration are shown and discussed. Capacitance measurements at various voltages, frequencies and temperatures are used to detect charges in lithium donor concentration and the formation of defects during irradiation. Physical models to explain the observed effects are presented.

Carter, J. R., Jr.↗
NASA NTRS1977

Current pyrheliometry for total solar irradiance observations

A Type IV active cavity radiometer (ACR IV) was developed at JPL in 1975-76 as part of the NASA Weather and Climate Program. It is capable of defining the absolute radiation scale with an uncertainty near 0.1% and a resolution of 0.02% at the nominal solar 'constant' level. The ACR IV is the first pyrheliometer capable of measurements at the 0.1% level, which is the threshold of solar 'constant' variability of significance for climatological modeling. A prototype has been tested, and a flight instrument was flown in a 1976 sounding rocket experiment which determined a solar 'constant' value of 1368 W/sq m. A three-detector version of the ACR IV is being developed to monitor the solar 'constant' during 1979-80 as part of NASA's Solar Maximum Mission. Another ACR IV will measure the solar 'constant' as part of the Spacelab I mission in 1980.

Willson, R. C.↗
NASA NTRS1978

The effect of finite geometry on the three-dimensional transfer of solar irradiance in clouds

Results are presented for a Monte Carlo model applied to a wide range of cloud widths and heights, and for an analytical model restricted in its application to cuboidally shaped clouds whose length, breadth, and depth may be varied independently; the clouds must be internally homogeneous with respect to their intrinsic radiative properties. Comparative results from the Monte Carlo method and the derived analytical model are presented for a wide range of cloud sizes, with special emphasis on the effects of varying the single scatter albedo, the solar zenith angle, and the scattering phase angle.

Davies, R.↗