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  • 1
    Electronic Resource
    Electronic Resource
    Decrease in the Period of Pulsar PSR 0833–45 (1969)
    [s.l.] : Nature Publishing Group
    Nature 222 (1969), S. 1260-1261 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] If the pulsar PSR 0833-45 increased its mass, M, by SM, conservation of angular momentum yields (assuming that 8M does not carry appreciable angular momentum) (1) where I(M) is moment of inertia, and Q! and Q,2 are the extrapolated angular velocities at the time the sudden decrease in period is ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/2221260a0
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  • 2
    Electronic Resource
    Electronic Resource
    Model Atmosphere Calculation of the Solar Oblateness (1969)
    [s.l.] : Nature Publishing Group
    Nature 221 (1969), S. 646-648 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The two basic assumptions made by Dicke and Goldenberg are that the surfaces of equal density and potential coincide, and that, if DF is due to a temperature difference, the difference in flux divided by the flux remains constant when the slit size used to measure the flux difference is increased. ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/221646b0
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  • 3
    Electronic Resource
    Electronic Resource
    On the sun's differential rotation (1974)
    Springer
    Solar physics 38 (1974), S. 301-309 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract It is assumed that the meridional motions (U) and angular velocity (Ω) in the surface layers of the convection zone are given by simple expressions of the form: U r = 2 ψ (r) P 2(cosθ)/ϱr 2, U 0 = −ψ′(r) sinθ cosθ/ϱr, and Ω = Ω 0[(1 + ω 0(r) + ω 2(r) P 2(cosθ)]. Here ψ(r) is the stream function, P 2(cosθ) the second order Legendre polynomial, and θ the polar angle. Allowance is made for a possible difference in the rate of momentum exchange between the directions parallel and perpendicular to gravity by introducing an anisotropic turbulent viscosity coefficient, μ, which is assumed furthermore to be proportional to the density, ϱ;μ = ϱν, and ν θθ = ν φφ = sν rr . It is shown that if the sunspots give an indication of the Sun's angular velocity at a depth h(∽ 3 × 104 km) then the turbulent viscosity is necessarily anisotropic. The radial variation introduced by this anisotropy seems to explain well the sunspot data if we assume that the sunspots act as tracers of the Sun's angular velocity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00155068
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  • 4
    Electronic Resource
    Electronic Resource
    On the solar oblateness: The combined effect of a pole-equator difference in effective temperature and mechanical heating (1971)
    Springer
    Solar physics 21 (1971), S. 21-26 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract With the help of a model atmosphere of the Sun we evaluate the pole-equator difference in flux (as measured by Dicke and Goldenberg) assuming the following type of pole-equator temperature difference (ΔT=T e −T p ): (a) ΔT ≈ 2K for τ 〉 τ0 (τ0 ≈ 0.05); (b) ΔT ≈ 10K for τ 〈 τ0. The small ΔT at all optical depths given by (a) could, for example, be due to a pole-equator difference in effective temperatures. At small optical depths a difference in mechanical heating could give rise to the larger temperature difference given by (b). We compare the results of our calculations with Dicke and Goldenberg's observations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00155768
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  • 5
    Electronic Resource
    Electronic Resource
    On the Sun's differential rotation and pole-equator temperature difference (1972)
    Springer
    Solar physics 26 (1972), S. 3-7 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The Sun's differential rotation can be understood in terms of a preferential stabilization of convection (by rotation) in the polar regions of the lower part of the convection zone (where the Taylor number is large). A significant pole-equator difference in flux (Δℱ) can develop deep inside the convection zone which would be unobservable at the surface, because ℱ can be very efficiently reduced by large scale meridional motions rising at the poles and sinking at the equator. This is the sense of circulation needed to produce the observed equatorial acceleration of the Sun. Differential rotation is generated, therefore, in the upper part of the convection zone (where the interaction of rotation with convection is small) and results as the convection zone adjusts to a state of negligible Taylor number.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00155099
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  • 6
    Electronic Resource
    Electronic Resource
    On coronal streamers with T-type neutral points (1975)
    Springer
    Solar physics 41 (1975), S. 233-240 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The gas-magnetic field interaction of an isothermal axisymmetric corona is considered. A method is suggested for solving the MHD equations in the case when a uniform gas pressure and the radial component of the magnetic field (as in a dipole) are specified at the Sun's surface. The flux of open field lines (φ) can be given arbitrarily, and no reconnection or opening of field lines can take place. If configurations in hydrostatic equilibrium between the regions of open and closed field lines can be found, then the method of solution converges. The equation of hydrostatic equilibrium at the neutral point (assumed to be of the T-type) is written in a simple form, and it is shown that if φ is smaller than a certain φmin, this equation cannot be satisfied. Configurations in hydrostatic equilibrium between the regions of open and closed field lines are expected to exist for any value of φ larger than φmin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00152970
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  • 7
    Electronic Resource
    Electronic Resource
    Solar-wind properties at the Earth as predicted by the two-fluid model (1973)
    Springer
    Solar physics 30 (1973), S. 223-234 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The two-fluid equations for the solar wind are written down in a simplified form, similar to that suggested by Roberts (1971) for the one-fluid model. The equations are shown to depend only on one parameter, $$K = GM\kappa _e m_p (\varepsilon _\infty T_0 )^{{3 \mathord{\left/ {\vphantom {3 2}} \right. \kern-\nulldelimiterspace} 2}} /4k^2 Fe,$$ , where G is the gravitational constant, M the mass of the star, κ e the thermal electron conductivity, m p the proton mass, k the Boltzman constant, kɛ ∞T0 the residual energy per particle at infinity and F e the electron-particle flux. For a variety of values of the density and temperature at the base of the corona we compute the solutions of the two-fluid solar wind model and compare the predicted and observed solar wind parameters at the Earth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00156191
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  • 8
    Electronic Resource
    Electronic Resource
    Solar-interplanetary modeling: 3-D solar wind solutions in prescribed non-radial magnetic field geometries (1975)
    Springer
    Solar physics 40 (1975), S. 461-486 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A model is presented which describes the 3-dimensional non-radial solar wind expansion between the Sun and the Earth in a specified magnetic field configuration subject to synoptically observed plasma properties at the coronal base. In this paper, the field is taken to be potential in the inner corona based upon the Mt. Wilson magnetograph observations and radial beyond a certain chosen surface. For plasma boundary conditions at the Sun, we use deconvoluted density profiles obtained from synopticK-coronameter brightness observations. The temperature is taken to be 2 × 106 K at the base of closed field lines and 1.6 x 106K at the base of open field lines. For a sample calculation, we employ data taken during the period of the 12 November 1966 eclipse. Although qualitative agreement with observations at 1 AU is obtained, important discrepancies emerge which are not apparent from spherically symmetric models or those models which do not incorporate actual observations in the lower corona. These discrepancies appear to be due to two primary difficulties - the rapid geometric divergence of the open field lines in the inner corona as well as the breakdown in the validity of the Spitzer heat conduction formula even closer to the Sun than predicted by radial flow models. These two effects combine to produce conductively dominated solutions and lower velocities, densities, and field strengths at the Earth than those observed. The traditional difficulty in solar wind theory in that unrealistically small densities must be assumed at the coronal base in order to obtain observed densities at 1 AU is more than compensated for here by the rapid divergence of field lines in the inner corona. For these base conditions, the value ofβ(ratio of gas pressure to magnetic pressure) is shown to be significantly greater than one over most of the lower corona - suggesting that, for the coronal boundary conditions used here, the use of a potential or force-free magnetic field configuration may not be justified. The calculations of this paper point to the directions where future research on solar-interplanetary modelling should receive priority: (a) better models for the coronal magnetic field structure (b) improved understanding of the thermal conductivity relevant for the solar wind plasma.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00162392
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  • 9
    Electronic Resource
    Electronic Resource
    Pulsation Periods of Rotating White Dwarfs (1968)
    [s.l.] : Nature Publishing Group
    Nature 219 (1968), S. 20-21 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] When uniform rotation is included, the periods of pulsation for white dwarfs can become as small as 0.9 s. With non-uniform rotation, periods as short as 0.1 s may be ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/219020a0
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  • 10
    Electronic Resource
    Electronic Resource
    Stability of Rotating Massive Stars in General Relativity (1965)
    [s.l.] : Nature Publishing Group
    Nature 208 (1965), S. 1304-1305 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] In a recent publication, Roxburgh6, using a virial theorem approach, found that rotation had a considerable stabilizing effect, changing the radius at which instability occurred by a very large factor. In view of the large change produced by rotation it is desirable to have a proper stability ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/2081304a0
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