The lowest eigenmode of thin axisymmetric shells is investigated for two physical models (acoustics and elasticity) as the shell thickness (2ε) tends to zero. Using a novel asymptotic expansion we determine the behavior of the eigenvalue λ(ε) and the eigenvector angular frequency k(ε) for shells with Dirichlet boundary conditions along the lateral boundary, and natural boundary conditions on th...

Recent analyses of the helioseismic observations indicate that the previously observed surface torsional oscillations with periods of about 11 years extend significantly downwards into the solar convective zone. Furthermore, there are indications that the dynamical regimes at the base of the convection zone are different from those observed at the top, having either significantly shorter period...

The small-scale magnetic helicity produced as a by-product of the large-scale dynamo is believed to play a major role in dynamo saturation. In a mean-field model the generation of small-scale magnetic helicity can be modelled by using the dynamical quenching formalism. Catastrophic quenching refers to a decrease of the saturation field strength with increasing Reynolds number. It has been sugge...

Symmetry-breaking bifurcations have been studied for convection in a nonrotating spherical shell whose outer radius is twice the inner radius, under the influence of an externally applied central force field with a radial dependence proportional to 1/r(5). This work is motivated by the GeoFlow experiment, which is performed under microgravity condition at the International Space Station where t...

Increasing observations are becoming available about a relatively weak, but persistent, non-axisymmetric magnetic field co-existing with the dominant axisymmetric field on the Sun. It indicates that the non-axisymmetric magnetic field plays an important role in the origin of solar activity. A linear non-axisymmetric α − Ω dynamo model is set up to discuss the characteristics of the axisymmetric...

Observations show that solar activity is distributed non-axisymmetrically, concentrating at “preferred longitudes”. This indicates the important role of non-axisymmetric magnetic fields in the origin of solar activity. We investigate the generation of the non-axisymmetric fields and their coupling with axisymmetric solar magnetic field. Our kinematic generation (dynamo) model operating in a sph...

This paper is concerned with the airway closure problem and investigates the quasi-steady deformation characteristics of strongly collapsed (buckled) airways occluded by liquid bridges of high surface tension. The airway wall is modeled as a thin-walled elastic shell, which deforms in response to an external pressure and to the compression due to the surface tension of the liquid bridge. The go...

Recent analyses of the helioseismic observations indicate that the previously observed surface torsional oscillations with periods of about 11 years extend significantly downwards into the solar convective zone. Furthermore, there are indications that the dynamical regimes at the base of the convection zone are different from those observed at the top, having either significantly shorter period...

Pressure spectra at large wave numbers are calculated for Lundgren-Townsend vortex models of the fine scales of homogeneous turbulence. Specific results are given for the Burgers vortex and also for the Lundgren-strained spiral vortex. For the latter case, it is fqund that the contribution to the shell-summed spectrum produced by the interaction between the axisymmetric and nonaxisymmetric comp...