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  • 11
    Publication Date: 2011-08-18
    Description: From an analysis of numerous reports from different locations on the duration of totality of the solar eclipses on January 24, 1925, and February 26, 1979, it is found that the solar radius at the earlier date was 0.5 arcsec (or 375 km) larger than at the later date. The correction to the standard solar radius found for each eclipse is different when different subsets of the observations are used (for example, edge of path of totality timings compared with central timings). This is seen as suggesting the existence of systematic inaccuracies in our knowledge of the lunar figure. The differences between the corrections for both eclipses, however, are very similar for all subsets considered, indicating that changes of the solar size may be reliably inferred despite the existence of the lunar figure errors so long as there is proper consideration of the distribution of the observations. These results are regarded as strong evidence in support of the occurrence of solar radius changes on shorter than evolutionary time scales.
    Keywords: SOLAR PHYSICS
    Type: Nature (ISSN 0028-0836); 304; Aug. 11
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  • 12
    Publication Date: 2011-08-18
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; vol. 252
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  • 13
    Publication Date: 2011-08-17
    Description: It is noted that although the 11 year solar cycle was first recognized in 1843, it is still only poorly understood. Further, while there are satisfactory models for the magnetic variations, the underlying physics is still obscure. New observations on the changing three-dimensional form of the solar wind are presented which help relate some of the modulations observed in geomagnetic activity, the ionosphere, and the flux of galactic cosmic rays.
    Keywords: SOLAR PHYSICS
    Type: AD-A099231 , AFGL-TR-81-0113 , Nature; 286; July 17
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  • 14
    Publication Date: 2011-08-19
    Description: Low-noise (S/N greater than 100), high spectral resolution observations of two pure rotation transitions of OH from the solar photosphere are used to make inferences concerning the thermal structure and inhomogeneity of the upper photosphere. It is found that the v = O R22(24.5)e line strengthens at the solar limb, in contradiction to the predictions of current one-dimensional photospheric models. The results for this line support a two-dimensional model in which horizontal thermal fluctuations in the upper photosphere are of the order plus or minus 800 K. 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 30-200-micron region.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics (ISSN 0038-0938); 94; 57-74
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  • 15
    Publication Date: 2011-08-18
    Description: The metric Type-II solar burst event of June 29, 1980, is characterized on the basis of spatially resolved radioheliograph observations obtained at Culgoora, Australia, and visible-light observations obtained with the coronograph/polarimeter of the SMM satellite. The data are presented in images, diagrams, and graphs and discussed in detail. The Type-II emission is found to arise in the dense moving material behind the transient loops, which have sky-plane width 0.5 solar radius and line-of-sight depth 0.1-0.4 solar radius. A faint arc observed moving ahead of the transient loops at about 900 km/sec and not associated with the Type-II burst is attributed to a shock front, and the compression ratio and Alfven Mach number of the enhanced-density region are estimated as n2/n1 = 1.3-3 and M(A) = 1.2-3. The ambient material at 3 solar radii is determined to have Alfven speed 250-625 km/sec and magnetic-field strength 50-120 mG. The total mass of the event is calculated as 700 Tg; the total magnetic energy of the loops is (1.5-15) x 10 to the 29th ergs.
    Keywords: SOLAR PHYSICS
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 134; 2, Ma
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  • 16
    Publication Date: 2011-08-18
    Description: Observations are presented of the corona during the June 11, 1983 total solar eclipse, together with preliminary results of a coordinated observing program conducted to investigate the relationship between the corona and the lower parts of the solar atmosphere. Synoptic observations of the white light corona and disk in H-alpha are compared with the eclipse image, together with the inferred longitudinal component of the photospheric magnetic field measured using the magnetically sensitive Fe line at 6303 A. Using these data, an interpretation of the global three-dimensional coronal structure is attempted; showing that the eclipse image contains bright features which are far from the plane of the sky, and that it is dominated by streamers over polar filament neutral lines.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 278; L123-L12
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  • 17
    Publication Date: 2013-08-31
    Description: Over 4500 absorption lines have been marked on the spectra and the corresponding line positions tabulated. The associated absorbing telluric or solar species for more than 90% of these lines have been identified and only a fraction of the unidentified lines have peak absorptions greater than a few percent. The high resolution and the low Sun spectra greatly enhance the sensitivity limits for identification of trace constituents.
    Keywords: SOLAR PHYSICS
    Type: NASA-CR-163499
    Format: application/pdf
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  • 18
    Publication Date: 2011-08-18
    Description: An analysis is made of interplanetary tangential and rotational solar wind discontinuities (TD and RD) and comparisons are made between the features of RDs and TDs. An ISEE 3 field and positive ion data set from 1978 includes high time resolution magnetometer data and is used for the comparisons, as are data from a positive ion analyzer. The field magnitude of RDs remains constant as the field rotates, while that of a TD passes through a local minimum. First and second adiabatic invariants for protons and He abundances are usually also conserved for RDs but not for TDs. The velocity change for an RD across a discontinuity is smaller than that predicted by MHD theory. Finally, plasma conditions at a discontinuity more closely resemble RDs than TDs.
    Keywords: SOLAR PHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 89; 5395-540
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  • 19
    Publication Date: 2011-08-18
    Description: Results for small loop thermal models of hard X-ray bursts are extended to large loops. In this model a magnetic arch with a coronal length of 45,000 km has the electrons near the top heated to temperatures above 1 billion K. The resulting conduction fronts which form are dominated by collisionless processes and travel down the arch to the transition region and chromosphere where they evaporate off part of the latter. This relatively cool material travels back up the loop and eventually quenches the source for energy injection times of order 10 sec. Most of the X-ray emission comes from the footpoints of the arch over most of the source lifetime and the spectrum is a power law with a typical spectral index of 3.0. Even though the efficiency gain in this model is only 2.8, it is much easier from the point of view of plasma physics to heat all the electrons in a plasma than to accelerate a substantial fraction of them.
    Keywords: SOLAR PHYSICS
    Type: ESA Plasma Astrophys.; p 401-404
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  • 20
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    In:  Other Sources
    Publication Date: 2011-08-17
    Description: The possibility that solar flare proton fluxes are limited in magnitude by saturation effects inherent to the acceleration mechanism is explored. If cyclotron damping of Alfven waves acts to accelerate protons, the criterion that the damping time is comparable to the acceleration time provides a fast particle number density at which protons load the wave spectrum. The limiting flux at 1 AU is obtained by a volume integration over the acceleration region and redistribution into an interplanetary emission cone. A simplified explosion model permits a delineation between volume and surface acceleration mechanisms in terms of a temporal parameter, the effective duration of acceleration. It is concluded that the limiting flux may be a realistic concept, but that further investigation is warranted to sharpen the criterion.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics; 67; Aug. 198
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