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  • SOLAR PHYSICS
  • 1980-1984  (324)
  • 1970-1974  (28)
  • 1
    Publication Date: 2011-08-18
    Description: Absorption features from the 8 micron SiO fundamental (upsilon = 1-0) and hot bands (upsilon = 2-1) have been observed in sunspots at sub-Doppler resolution using a ground-based tunable diode laser heterodyne spectrometer. The observed line widths suggest an upper limit of 0.5 km/s for the microturbulent velocity in sunspot umbrae. Since the silicon monoxide abundance is very sensitive to sunspot temperature, the measured equivalent widths permit an unambiguous determination of the temperature-pressure relation in the upper layers of the umbral atmosphere. In the region of SiO line formation (log P sub g = 3.0-4.5), the results support the sunspot model suggested by Stellmacher and Wiehr (1970).
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 269; June 1
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  • 2
    Publication Date: 2011-08-18
    Description: A decrease in the solar radius is determined using the technique of Dunham and Dunham (1973), in which timed observations are made just inside the path edges. When the method is applied to the solar eclipses of 1715, 1976, and 1979, the solar radius for 1715 is 0.34 + or - 0.2 arc second larger than the recent values, with no significant change between 1976 and 1979. The duration of totality is examined as a function of distance from the edges of the path. Corrections to the radius of the sun derived from observations of the 1976 and 1979 eclipses by the International Occultation Timing Association are also presented.
    Keywords: SOLAR PHYSICS
    Type: Science; 210; Dec. 12
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  • 3
    Publication Date: 2013-08-31
    Description: The decomposition of solar oscillations into their constituent normal modes requires a knowledge of both the spatial and temporal variation of the perturbation to the Sun's surface. The task is especially difficult when only limited spatial information is available. Observations of the limb darkening function, for example, are probably sensitive to too large a number of modes to permit most of the modes to be identified in a power spectrum of measurements at only a few points on the limb, unless the results are combined with other data. A procedure was considered by which the contributions from quite small groups of modes to spatially well resolved data obtained at any instant can be extracted from the remaining modes. Combining these results with frequency information then permits the modes to be identified, at least if their frequencies are low enough to ensure that modes of high degree do not contribute substantially to the signal.
    Keywords: SOLAR PHYSICS
    Type: NAS 1.26:173667 , NASA-CR-173667
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  • 4
    Publication Date: 2013-08-31
    Description: Low energy electron measurements collected by ISEE 1 reveal the frequent presence of field-aligned fluxes of few hundred eV electrons in he geomagnetic tail lobes. In the northern tail lobe these electrons are most prominent when the interplanetary magnetic field is directed away from the Sun. This characteristic helps identify the electrons as polar rain electrons. By mapping the tail lobe velocity distribution function into the solar wind, previous suggestions that the polar rain is indeed of solar wind origin and is due to the access of electrons to the magnetotail lobe were confirmed. It was demonstrated that the moe energetic component of the polar rain is composed of electrons from the solar wind strahl - a field-aligned component of the solar wind which is difficult to measure but which is thought to be caused by the collisionless transit of hundred eV electrons from the inner solar corona to 1 AU.
    Keywords: SOLAR PHYSICS
    Type: NAS 1.15:86150 , NASA-TM-86150
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  • 5
    Publication Date: 2013-08-31
    Description: Low noise high spectral resolution observations of two pure rotation transitions of OH from the solar photosphere were obtained. The observations were obtained using the technique of optically null-balanced infrared heterodyne spectroscopy, and consist of center-to-limb line profiles of a v=1 and a v=0 transition near 12 microns. These lines should be formed in local thermodynamic equilibrium (LTE), and are diagnostics of the thermal structure of the upper photosphere. The v=0 R22 (24.5)e line strengthens at the solar limb, in contradiction to the predictions of current one dimensional photospheric models. Data for this line support a two dimensional model in which horizontal thermal fluctuations of order + or - 800K occur in the region Tau (sub 5000) approximately .001 to .01. This thermal bifurcation may be maintained by the presence of magnetic flux tubes, and may be related to the solar limb extensions observed in the 30 to 200 micron region.
    Keywords: SOLAR PHYSICS
    Type: NASA-TM-86128 , NAS 1.15:86128
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  • 6
    Publication Date: 2016-06-07
    Description: Methods for predicting the path edges and reducing observations of total solar eclipses for determining variations of the solar radius are described. Analyzed observations of the 1925 January eclipse show a 0.7 (arc second) decrease in the solar radius during the past fifty years.
    Keywords: SOLAR PHYSICS
    Type: Variations of the Solar Constant; p 117-120
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  • 7
    Publication Date: 2006-01-16
    Description: The adaptation of proven space probe technology is proposed as a means of providing a solar activity monitoring platform which could be injected behind the Earth's orbital position to give 3 to 6 days advanced coverage of the solar phenomenon on the backside hemisphere before it rotates into view and affects terrestrial activities. The probe would provide some three dimensional discrimination within the ecliptic latitude. This relatively simple off-Earth probe could provide very high quality data to support the SCADM program, by transmitting both high resolution video data of the solar surface and such measurements of solar activity as particle, X-ray, ultraviolet, and radio emission fluxes. Topics covered include the orbit; constraints on the spacecraft; subsystems and their embodiments; optical imaging sensors and their operation; and the radiation-pressure attitude control system are described. The platform would be capable of mapping active regions on an hourly basis with one arc-second resolution.
    Keywords: SOLAR PHYSICS
    Type: NASA. Goddard Space Flight Center Study of the Solar Cycle from Space; p 45-54
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  • 8
    Publication Date: 2011-08-16
    Description: The present work proposes a general rule relating the polarity of broad-band (spectral range: 5250 A to 5350 A) circular polarization fields observed in sunspots to that of the corresponding magnetic fields. The rule is illustrated with observations of particular spots.
    Keywords: SOLAR PHYSICS
    Type: Astronomy and Astrophysics; 37; 1, De; Dec. 197
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  • 9
    Publication Date: 2011-08-16
    Keywords: SOLAR PHYSICS
    Type: Astronomy and Astrophysics; 35; 3, Oc; Oct. 197
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  • 10
    Publication Date: 2011-08-19
    Description: A comparison between proton events and coronal mass ejections (CMEs) based on nearly three years of observations around the recent maximum of solar activity is presented. Peak proton fluxes are found to correlate with both the speeds and the angular sizes of the associated CMEs. It is shown that CME speeds do not significantly correlate with CME angular sizes, so that peak proton fluxes are correlated with two independent CME parameters. With larger angular sizes, CMEs are more likely to be loops and fans rather than jets and spikes and are more likely to intersect the ecliptic.
    Keywords: SOLAR PHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 89; 9683-969
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