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  • 1
    Electronic Resource
    Electronic Resource
    Variations in solar luminosity and their effect on the Earth's climate (2006)
    [s.l.] : Nature Publishing Group
    Nature 443 (2006), S. 161-166 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Variations in the Sun's total energy output (luminosity) are caused by changing dark (sunspot) and bright structures on the solar disk during the 11-year sunspot cycle. The variations measured from spacecraft since 1978 are too small to have contributed appreciably to accelerated global ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nature05072
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  • 2
    Electronic Resource
    Electronic Resource
    Theoretical interpretation of total solar irradiance variations
    Amsterdam : Elsevier
    Advances in Space Research 8 (1988), S. 43-50 
    Details
    ISSN: 0273-1177
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0273-1177(88)90171-8
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  • 3
    Electronic Resource
    Electronic Resource
    A Possible observational correlation of lunar luminescence with the K"p index
    Amsterdam : Elsevier
    Icarus 9 (1968), S. 162-174 
    Details
    ISSN: 0019-1035
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/0019-1035(68)90010-9
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  • 4
    Electronic Resource
    Electronic Resource
    Comment on ‘average photospheric poloidal and toroidal magnetic field components near solar minimum’ by Duvall et al. (1980)
    Springer
    Solar physics 67 (1980), S. 9-12 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We discuss the dynamical interpretation of evidence for an azimuthal tilt of the global magnetic field from the radial direction at the photosphere. We point out that the Reynolds stresses of supergranular convective motions might produce the required small tilt of intense flux tubes, without implying an unacceptably large momentum flux across the photospheric surface into the solar wind. Our calculations lead us to conclude that there is little reason, at present, to infer (Duvall et al., 1979) a separate low intensity constituent of the global magnetic field, from the observational evidence for an azimuthal tilt. More precise measurements of the vertical component of supergranular motions would be useful in determining the actual torque exerted by the Reynolds stresses on the magnetic field.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00146677
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  • 5
    Electronic Resource
    Electronic Resource
    The temperature structure and pressure balance of magnetic loops in active regions (1975)
    Springer
    Solar physics 43 (1975), S. 327-336 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract EUV observations show many active region loops in lines formed at temperatures between 104K and 2×l06K. The brightest loops are associated with flux tubes leading to the umbrae of sunspots. It is shown that the high visibility of certain loops in transition region lines is due principallly to a sharp radial decrease of temperature to chromospheric values toward the loop axis. The plasma density of these cool loops is not significantly greater than in the hot gas immediately surrounding it. Consequently, the internal gas pressure of the cool material is clearly lower. The hot material immediately surrounding the cool loops is generally denser than the external corona by a factor 3–4. When the active region is examined in coronal lines, this hot high pressure plasma shows up as loops that are generally parallel to the cool loops but significantly displaced laterally. In general the loop phenomenon in an active region is the result of temperature variations by two orders of magnitude and density variations of around a factor five between adjacent flux tubes in the corona.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00152357
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  • 6
    Electronic Resource
    Electronic Resource
    Erratum (1970)
    Springer
    Astrophysics and space science 6 (1970), S. 340-340 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00651236
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  • 7
    Electronic Resource
    Electronic Resource
    Sunspot bright rings and the thermal diffusivity of solar convection (1983)
    Springer
    Solar physics 84 (1983), S. 33-44 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We have used the 512 channel diode array and vacuum telescope at KPNO to study the photospheric intensity distribution around sunspots, for comparison with isotherms predicted by convective blocking models of heat flow. Raster scan observations of 10 spots on 18 days were carried out in 1980 and 1981. Continuum passbands of 0.25 Å width were selected to avoid contamination by weak Fraunhofer lines, whose strength is sensitive to the presence of magnetic faculae often found near spots. Our observations show no evidence of extended bright rings around the spots at the level of 1–2%, as reported in one recent study using photographic photometry and much wider passbands. But 6 of the 10 spots we measured show marginally significant (2–3σ) bright rings of peak amplitude 0.1–0.3%. We are not able to explain these rings as a result of either residual facular signal, or instrumental effects. The excess radiative flux in these rings is small compared to the missing flux in the spot umbra and penumbra. We compare the brightness of the observed rings with peak brightnesses calculated from models of heat flow around spots of various depths and radii. Even if the spot is assumed to be unrealistically shallow, a detectable bright ring requires that the effective thermal conductivity (and/or its depth gradient) in layers surrounding the spot be significantly lower than the values indicated by mixing length models of the solar convection zone.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00157440
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  • 8
    Electronic Resource
    Electronic Resource
    On the interpretation of Fraunhofer line Doppler shifts at supergranule boundaries (1984)
    Springer
    Solar physics 92 (1984), S. 33-46 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We have used the SPO tower telescope and echelle spectrograph to study differences in the profiles of three Fei lines, between magnetic network and cells. Ca K slit-jaw pictures were used to identify the network and cell areas, and mean network and cell profiles were computed from digitized spectra for the g = 0 lines λλ4065, 5434, and the g = 1.5 line λ 5233. The profile bisectors show that the wings of all three lines are red-shifted in the network by between 75–200 m s−1 relative to the cell profiles. But the redshift decreases in the line core and becomes less than the standard error of 20 m s−1 near the line core minimum. This disappearance of the redshift at the cores of all 3 lines formed over the height range 250–500 km above τ 0.5 = 1, argues against a steady downflow at supergranule boundaries. We show that such red-shifted wings and a relatively unshifted core can result if granular convection is suppressed near the network flux tubes, without implying any downflow in the vicinity of these flux tubes. Our results also indicate that searches for large-scale convective velocity patterns should measure shifts of the line core, rather than the line wings which appear to be very sensitive to inhomogeneities in granule structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00157232
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  • 9
    Electronic Resource
    Electronic Resource
    Paschen-line Stark-broadening as an electric field diagnostic in erupting prominences (1988)
    Springer
    Solar physics 114 (1988), S. 65-73 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We analyse the Stark broadening of the Balmer and Paschen lines emitted in two bright eruptive prominences, to determine the total electric field in these structures. We show that the Paschen lines provide a significantly more sensitive and accurate electric field indicator than the Balmer lines used previously in such studies. In the two eruptive events analysed here, the total electric fields agree to within 5–10 V cm-1 with the pressure-broadening fields expected from local densities of the cool plasma, measured simultaneously and co-spatially by a line-ratio diagnostic. We conclude that in such structures the upper limit to any widespread macroscopic fields is roughly 10 V cm-1 or less. This is in agreement with the motional electric field that might be associated with reconnection at the observed rate of the prominences' outward motion of about 135 km s-1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00193067
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  • 10
    Electronic Resource
    Electronic Resource
    A photometric search for solar giant convection cells (1987)
    Springer
    Solar physics 110 (1987), S. 129-138 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We limit the photometric contrast of solar giant convection cells using λ525.6 nm continuum images obtained on 15 days in May 1985. The r.m.s. of the giant cell intensity pattern must be less than or equal to the observed r.m.s. on spatial scales 80 to 240 Mm which is 0.023% or, equivalently, 0.33 K. However, the spatial scale and time-scale dependence of the variance demonstrate that giant cells are not the source of the observed variance. Consequently, a tighter constraint on the r.m.s. of the giant cell pattern may be placed, namely 0.016% or 0.23 K. This limit is consistent with temperature perturbations estimated from recent nonlinear simulations of global-scale solar convection. We use this limit on the r.m.s. of the giant cell pattern to estimate that the contribution of giant cells to the fluctuation of the solar irradiance on a one-month time-scale is less than 3 × 10−5 S.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00148208
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