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  • 1
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The Sun is not a rigid body and it is well known that its surface rotation is differential, the polar regions rotating substantially slower than the equator. This differential rotation has been demonstrated by helioseismology to continue down to the base of the convective zone, below which it becomes closer to a rigid body rotation. Far deeper, inside the energy generating core, the rotation has generally been assumed to be much faster, keeping memory of the presumably high speed of the young Sun. However, several recent results of helioseismology have decreased this likelihood more and more, so that the core rotation could be suspected to be only marginally, or even not at all faster than the envelope. Certain results would even imply a core rotation slower than the envelope, an interesting but unlikely possibility. We present here a complete analysis of the rotational splitting of the low degree modes measured in three different time series obtained in 1990, 1991, and 1992 by the IRIS full-disk network. With a time of integration slightly longer than 4 months, the splitting has been measured by 4 different global methods on 42 doublets of l = 1, 35 triplets of l = 2, and 30 quadruplets of l = 3. With a high level of confidence, our result is consistent with a rigid solar core rotation.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Solar physics 133 (1991), S. 13-30 
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract In the framework of the IRIS programme, full-disk solar Doppler-shift measurements are made with an optical resonance sodium cell spectrophotometer, a new pattern of the instrument successfully used at the geographic South Pole 10 years ago. After many successive improvements, the IRIS version has now become a precise and reliable device, being limited only by the solar and/or by the atmospheric noise in all the frequency ranges of interest for the p-mode and the g-mode investigation. This instrument is described here in some detail, with the technical specification for each individual component being defined by comparison to the photon and the solar noise.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Astrophysics and space science 188 (1992), S. 137-142 
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract High-speed photometric data obtained for a number of white-dwarf stars confirm the presence of subharmonic frequency in their power spectra. As many of these white dwarfs show multiperiodic structures, we show that the break up of quasi-periodic motion results in the appearance of similar subharmonic components in their spectra.
    Type of Medium: Electronic Resource
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