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  • 1
    Publication Date: 2019-08-28
    Description: The center-to-limb variation of the He II 304- and 256-A lines and He I 584- and 537-A lines is derived for different solar features, but averaged over the chromospheric supergranulation structure. The general trend is for limb brightening in quiet-sun regions, limb neutrality in unipolar magnetic regions (UMR), and limb darkening in polar coronal holes. The center-to-limb behavior in these optically thick emission lines indicates collisional excitation and decreasing transition-region temperature gradients with respect to optical depth in the sequence quiet sun to UMR to coronal hole.
    Keywords: SOLAR PHYSICS
    Type: PB80-118110 , Astrophysical Journal; vol. 220
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  • 2
    Publication Date: 2019-07-13
    Description: Digital image processing of eight solar flare events was performed using the Video Information Communication and Retrieval language in order to study moving emission fronts, flare halos, and Moreton waves. The techniques used include contrast enhancement, isointensity contouring, the differencing of images, spatial filtering, and geometrical registration. The spatial extent and temporal behavior of the faint phenomena is examined along with the relation of the three types of phenomena to one another. The image processing techniques make possible the detailed study of the history of the phenomena and provide clues to their physical nature.
    Keywords: SOLAR PHYSICS
    Type: Conference on Applications of Digital Image Processing to Astronomy; Aug 20, 1980 - Aug 22, 1980; Pasadena, CA
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  • 3
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    In:  Other Sources
    Publication Date: 2019-06-27
    Description: The latitudinal component of solar differential rotation and the possibility of a radial component are discussed and compared to the observed rotational velocities of solar filaments. The author's values of rotational rate versus heliographic latitude for 100 points in the solar atmosphere derived from 17 quiescent filaments are shown to be comparable to the rates found by d'Azambuja and d'Azambuja (1948). The filament rate is significantly greater than the spot rate (Newton and Nunn, 1951); the difference cannot be accounted for by the poleward migration of filaments and seems to reflect a true radial gradient of rotational velocity in the sun. It is shown that filaments in closer proximity to active regions usually exhibit no differential rotation, while those far from active regions generally show it clearly. Comparison with Mt. Wilson photospheric Doppler measurements shows that filaments rotate faster than the general photosphere and that the spot rate exceeds that for the general photosphere.
    Keywords: SPACE SCIENCES
    Type: Solar Physics; 36; May 1974
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  • 4
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    In:  Other Sources
    Publication Date: 2019-06-27
    Description: The absence of preferential longitudes for emerging flux regions (EFRs) on the sun indicates that sunspot preferential longitudes, if they exist, are due to favorable longitudes for EFRs to become spot groups rather than to the distribution of points of emergence of EFRs. A short-lived 'preferential latitude' (classical activity complex) is found. The latitudinal distribution of all EFRs exhibits a Maunders diagram behavior as expected on the basis of data for the fraction of EFRs which become spot groups. Possibly significant nonrandom behavior of the EFR time distribution is also found.
    Keywords: SPACE RADIATION
    Type: Astronomical Society of the Pacific; vol. 85
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  • 5
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    In:  Other Sources
    Publication Date: 2019-06-27
    Keywords: SOLAR PHYSICS
    Type: Solar Physics; 41; Mar. 197
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  • 6
    Publication Date: 2019-06-28
    Description: The use of two dimensional Fast Fourier Transforms (FFTs) subjected to pattern recognition technology for the identification and classification of low altitude stratus cloud structure from Geostationary Operational Environmental Satellite (GOES) imagery was examined. The development of a scene independent pattern recognition methodology, unconstrained by conventional cloud morphological classifications was emphasized. A technique for extracting cloud shape, direction, and size attributes from GOES visual imagery was developed. These attributes were combined with two statistical attributes (cloud mean brightness, cloud standard deviation), and interrogated using unsupervised clustering amd maximum likelihood classification techniques. Results indicate that: (1) the key cloud discrimination attributes are mean brightness, direction, shape, and minimum size; (2) cloud structure can be differentiated at given pixel scales; (3) cloud type may be identifiable at coarser scales; (4) there are positive indications of scene independence which would permit development of a cloud signature bank; (5) edge enhancement of GOES imagery does not appreciably improve cloud classification over the use of raw data; and (6) the GOES imagery must be apodized before generation of FFTs.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: NASA-CR-173727 , JPL-PUB-84-17 , NAS 1.26:173727
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  • 7
    Publication Date: 2019-06-28
    Description: The long term effects of encapsulation individual sheets of the Codex Hammer were investigated. The manuscript was simulated with similar sheets of paper which were photographed under repeatable raking light conditions to enhance their surface texture, encapsulated in plexiglas, cycled in an environmental test chamber, and rephotographed at selected intervals. The film images were digitized, contrast enhanced, geometrically registered, and apodized. An FFT analysis of a control sheet and two experimental sheets indicates no micro-burnishing, but reveals that the ""mesoscale'' deformations with sizes 8mm are degrading monotonically, which is of no concern. Difference image analysis indicates that the sheets were increasingly stressed with time and that the plexiglas did not provide a sufficient environmental barrier under the simulation conditions. The relationship of these results to the Codex itself is to be determined.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: NASA-CR-173200 , JPL-PUB-83-75 , NAS 1.26:173200
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  • 8
    Publication Date: 2019-06-28
    Description: Techniques to integrate meteorological data from various satellite sensors to yield a global measure of sea surface wind speed and direction for input to the Navy's operational weather forecast models were investigated. The sensors were launched or will be launched, specifically the GOES visible and infrared imaging sensor, the Nimbus-7 SMMR, and the DMSP SSM/I instrument. An algorithm for the extrapolation to the sea surface of wind directions as derived from successive GOES cloud images was developed. This wind veering algorithm is relatively simple, accounts for the major physical variables, and seems to represent the best solution that can be found with existing data. An algorithm for the interpolation of the scattered observed data to a common geographical grid was implemented. The algorithm is based on a combination of inverse distance weighting and trend surface fitting, and is suited to combing wind data from disparate sources.
    Keywords: OCEANOGRAPHY
    Type: NASA-CR-174162 , NAS 1.26:174162
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  • 9
    Publication Date: 2019-06-27
    Keywords: ASTROPHYSICS
    Type: PB80-144215 , Astrophysical Journal Supplement Series; 41; Nov. 197
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  • 10
    Publication Date: 2019-06-27
    Keywords: SOLAR PHYSICS
    Type: PB-284726 , Astrophysical Journal; vol. 222
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