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[en] Starting with basic data, a dynamical model is derived for the velocity dispersion in the bulge of M31. There is good agreement between the r.m.s. components and the experimental range. (C.F.)
[en] Transverse magnetic (TM) modes with phase velocities at or just below the speed of light, c, are intended to accelerate relativistic particles in hollow-core, photonic band gap (PBG) fibers. These are so-called 'surface defect modes', being lattice modes perturbed by the defect to have their frequencies shifted into the band gap, and they can have any phase velocity. PBG fibers also support so-called 'core defect modes' which are characterized as having phase velocities always greater than c and never cross the light line. In this paper we explore the nature of these two classes of accelerating modes and compare their properties.
[en] The effect of flowing metal walls on the resistive wall instabilities is analyzed for a general cylindrically symmetric diffusive pinch configuration. Two types of liquid metal flow are analyzed: a uniform flow which is poloidally symmetric, and a two-stream flow consisting of two opposite streams splitting at the top and merging at the bottom. It is found in both configurations that when the liquid wall flow velocity exceeds a critical value, the resistive wall mode is stabilized. However, for the two-stream flow the critical velocity is several times smaller than that for the uniform flow. Still in a realistic experiment one needs a flow velocity of a few tens m/s to stabilize the resistive wall mode
[en] On the basis of a two-component (two-fluid) hydrodynamic model, it is shown that the probable phenomenon of solar core rotation with a velocity higher than the average velocity of global rotation of the Sun, discovered by the SOHO mission, can be related to fast solid-body rotation of the light hydrogen component of the solar plasma, which is caused by thermonuclear fusion of hydrogen into helium inside the hot dense solar core. Thermonuclear fusion of four protons into a helium nucleus (α-particle) creates a large free specific volume per unit particle due to the large difference between the densities of the solar plasma and nuclear matter. As a result, an efficient volumetric sink of one of the components of the solar substance—hydrogen—forms inside the solar core. Therefore, a steady-state radial proton flux converging to the center should exist inside the Sun, which maintains a constant concentration of hydrogen as it burns out in the solar core. It is demonstrated that such a converging flux of hydrogen plasma with the radial velocity vr(r) = −βr creates a convective, vr∂vφ/∂r, and a local Coriolis, vrvφ/r,φ nonlinear hydrodynamic forces in the solar plasma, rotating with the azimuthal velocity vφ. In the absence of dissipation, these forces should cause an exponential growth of the solid-body rotation velocity of the hydrogen component inside the solar core. However, friction between the hydrogen and helium components of the solar plasma due to Coulomb collisions of protons with α-particles results in a steady-state regime of rotation of the hydrogen component in the solar core with an angular velocity substantially exceeding the global rotational velocity of the Sun. It is suggested that the observed differential (liquid-like) rotation of the visible surface of the Sun (photosphere) with the maximum angular velocity at the equator is caused by sold-body rotation of the solar plasma in the radiation zone and strong turbulence in the tachocline layer, where the turbulent viscosity reaches its maximum value at the equator. There, the tachocline layer exerts the most efficient drag on the less dense outer layers of the solar plasma, which are slowed down due to the interaction with the ambient space plasma (solar wind).
[en] The rotation of 47 Tuc (NGC 104) was determined using the radial velocity of 159 stars listed in the catalogue of Major et al. (1983). The rotation parameters are functions of the distance from the center of the cluster. In the center the projection of the angular velocity is of the order of 10-5 yr-1 and decreases rapidly with the distance