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1.
S. M. Molodensky 《Izvestiya Physics of the Solid Earth》2011,47(7):559-574
In the first part of the paper [Molodenskii, 2011], we considered the problem of ambiguity in the solution of the inverse
problem of retrieval of density distribution in the Earth’s core and mantle and determination of the Q factors in the mantle
from the entire set of modern data on seismic velocities (V
p
and V
S
), the frequencies f
i
and quality factors Q
i
of free oscillations of the Earth, and the amplitudes and phases of its forced nutations. We have constructed the model distributions
of these parameters, in which the root-meansquared (rms) deviations of all observed values from the predicted ones are much
smaller than in the PREM model. Below, we compare the observed amplitudes of the forced nutation with the values predicted
by our model. In order to understand how rigid are the constraints imposed by the amplitudes of forced nutation, we not only
calculate the deviations of the observed amplitudes of nutation from the predictions by our model but also estimate the changes
in these deviations caused by small variations in several parameters of the model. To the parameters to be varied we refer
those which have no or barely any effect on the periods and damping constants of free oscillations but have a pronounced effect
on the amplitudes of forced nutation. These parameters include (1) the rheological properties of the mantle in the interval
of periods from an hour to a day; (2) the dynamical flattening of the liquid core; (3) the dynamic flattening of the solid
inner core; (4) the viscosity of the liquid core; and (5) the moment of inertia of the solid inner core. In addition, we estimate
the effects of variations in the moment of inertia of the liquid core to be small (±0.2%) and not to affect, within the observation
error, the periods of free oscillations. We show that the uncertainty in the model depth distributions of density considerably
decreases when the new data on the amplitudes and phases of the forced nutation of the Earth are taken into account. With
these data, it is possible to estimate the creep function for the lower mantle in a wide range of periods from a second to
a day. 相似文献
2.
Model calculations of plasma drifts in the solar corona were performed. We established that only drifts in crossed fields could result in velocities V of several hundred kilometers per second. Such velocities are typical of coronal mass ejections (CMEs). We derived an analytic expression for V where n, the expansion harmonic of the magnetic-field strength, varies with time. As follows from this expression, V is a power function of the distance with index (2?n) and the radial component changes sign (n?1) times in the latitude range from ?π/2 to +π/2. We found that if the magnetic dipole moment varies with time, the similarity between the spiral structures of coronal plasma is preserved when they displace within several solar radii and the density gradient at the conical boundaries increases (the apparent contrast is enhanced). There is a correspondence between the inferred model effects and the actually observed phenomena that accompany CMEs. 相似文献
3.
M. M. Molodensky 《Solar physics》1975,43(2):311-316
The exact limit of stability of force-free fields for the case α=const and spherical region of the disturbances is obtained. The stable fields of active regions must be close to the harmonical ones for length scales which are less than the linear dimensions of spots. 相似文献
4.
The problem to compute the magnetic field above the chromosphere using data of the vector = B
t/Bt that gives the projected field direction can be solved with different approximations. The field of direction vectors is, however, not the only field accessible to observations. The Stokes parameters, which are components of the radiation tensor, can be measured at each point of the image plane. The directions of the eigenvectors of the radiation tensor define two mutually orthogonal systems of integral curves in the image plane. These families of curves have singular points, which are generally of different type than those of the vector field. When the morphology of H chromospheric fibrils are used to infer the topology of the magnetic field, a similar problem is met, suggesting that singular points should also be present there. 相似文献
5.
S. M. Molodensky 《Izvestiya Physics of the Solid Earth》2008,44(7):519-526
Asymptotic analysis of low-frequency oscillations of a rotating liquid bounded by a solid surface is performed under the condition
that the oscillation frequency is much smaller than the angular rate of rotation. Simple analytical relations describing comprehensively
asymptotic modes of these oscillations are obtained. 相似文献
6.
M. M. Molodensky 《Astronomy Letters》2001,27(9):590-595
The expansion of solar coronal plasma is considered for the model described in Koutchmy et al. (1999). In addition to a spherical solar surface, the initial configuration represents a heliospheric sheet of dense plasma in the dipole equatorial plane. The heliospheric-sheet current decreases with distance as 1/r 2, with its sign being opposite to the sign of the initial-dipole current. The latter follows from the fact that the plasma sheet is denser than the surrounding corona and that the equilibrium condition for the sheet in the gravitational and magnetic fields is satisfied. The field lines of this configuration are nearly straight. We have obtained a general solution of the steady-state MHD equations, which depends not only on distance r but also on latitude θ. Applicability of the solution to interpreting observational data, in particular, those obtained from the Ulysses spacecraft, is discussed. 相似文献
7.
M. M. Molodensky 《Solar physics》1976,49(2):279-282
The condition of stability obtained earlier is generalized for the case of arbitrary force-free fields (f.f.f.). It is shown that the configurations are stable, if the ratio of the current to the field and its gradient are small enough. 相似文献
8.
S. M. Molodensky 《Solar System Research》2005,39(1):54-72
In the first part of this study (Molodensky, 2004; hereinafter, paper I), a survey of the theory of tides and nutation of the Earth was given with the inclusion of the dynamical effects of the elastic mantle and liquid core in the framework of a very simple model of a homogeneous, incompressible core. Here, effects of the inhomogeneity, compressibility, and viscosity of the liquid core are considered, along with those of electromagnetic coupling of the liquid core with the mantle and solid inner core. Errors in the present-day measurements of the amplitudes of forced nutation (of the order of 20 arc s) are well below not only the dynamical effects of the Earths liquid core but also the effects of the inelasticity of the mantle, the dynamical effects of the solid inner core, and the possible effects of electromagnetic coupling between the liquid core, solid inner core, and mantle. This opens up new avenues for astrometric studies of the mechanical properties and electrical conductivity of the mantle and solid inner core at very low frequencies. The modern data on the amplitudes and phases of the Earths forced nutation cannot be interpreted entirely unambiguously, since the following factors remain unknown: (i) the role of the core-mantle electromagnetic coupling compared to the coupling due to core viscosity near the core-mantle boundary and (ii) the frequency dependence of the creep function of the mantle at low frequencies. In large measure, the effects of electromagnetic and viscous coupling can be separated if high-precision data on the tidal variations in the gravitational force at periods of about a day are invoked and allowances are made for the differences between the effects of viscous and electromagnetic coupling on the amplitudes and phases of forced nutation and on the tidal variations in the gravitational force. Here, ranges of possible values of the creep function are constructed for periods from one hour to one day; for these calculations, values consistent with the entire set of data on the forced nutation of the Earth are assumed for the effective dynamical flattening of the liquid core-mantle and liquid core-solid inner core boundaries (these values describe the ellipticity of the boundaries of the inner core, outer core, and mantle, as well as the electromagnetic coupling between the liquid core, mantle, and solid inner core).Translated from Astronomicheskii Vestnik, Vol. 39, No. 1, 2005, pp. 61–80.Original Russian Text Copyright © 2005 by Molodensky. 相似文献
9.
We consider two types of streamer structures observed in the solar atmosphere. Structures of the first type are medium-scale configurations with scale lengths comparable to the scale height in the corona, kT/mg = 100 thousand km, which appear as characteristic plasma structures in the shape of a dome surrounding the active region with thin streamers emanating from its top. In configurations of this type, gravity plays no decisive role in the mass distribution. The plasma density is constant on magnetic surfaces. Accordingly, the structure of the configurations is defined by the condition ψ = const, where ψ is the flux function of the magnetic field. Structures of the second type are large-scale configurations (coronal helmets, loops, and streamers), which differ from the above structures in that their scale lengths exceed the scale height in the corona. For them, gravity plays a decisive role; as a result, instead of the magnetic surfaces, the determining surface is BgradΦ = 0. We constructed three-dimensional images of these structures. Some of the spatial curves called “visible contours” of the Br = 0 surface are shown to be brightest in the corona. We assume that the helmet boundaries and polar plumes are such curves. 相似文献
10.