Dynamic Mobility of Two Spherical Particles with Thick Double Layers

The dynamic electrophoretic mobility of a pair of nearby spherical particles is analyzed in the case when the thickness of the electrical double layer around each particle is comparable to the particle radius. By means of an integral reciprocal relation, a formal expression is obtained for the force and torque on N spheres subject to an oscillating electric field which may be spatially varying. Upon linearizing in the surface potential, this expression is shown to depend upon a set of purely hydrodynamic problems involving N neutral spheres, the calculation of the electric field around N neutral spheres, and the equilibrium charge distribution around N charged spheres. In the case of a single particle, the known analytic formula for the dynamic mobility is recovered. For a pair of identical particles, the dynamic mobility is calculated numerically, using known solutions to the required subproblems. An analytical expression for the mobility of a pair of widely separated spheres is also obtained by a method of reflections, and this is in excellent agreement with the numerical results outside the range of double layer overlap. Copyright 2000 Academic Press.     

Interaction of high-speed and transient fluxes of solar wind at the maximum of solar cycle 24

The interaction of the interplanetary coronal mass ejection (ICME) and the high-speed solar wind flux (HSSWF) associated with the coronal hole (CH) is considered. By the examples of two events at the maximum of solar cycle 24 from June 4 to June 16 and from June 30 to July 10, 2012 it is shown that the temperature-dependent parameters of the SW ionic composition appear closer to the values in the HSSWF than in the ICME due to mixing of fluxes in the corona when the ICME source is near the CH boundary.     

Problem of a solid half-space melted by a hot rotating disk or ring

The sliding friction of solids at high speed and under heavy load may be accompanied by a transition to the plastic or fluid state in the friction contact zone [1]. The stage corresponding to a developed fluid layer is investigated without taking into account the plastic deformation of the rubbing bodies; it is assumed that all the heat released is expended exclusively on melting the solid. Previous attempts to investigate this stage theoretically have been based on the approximation of a fluid layer of constant thickness and the use of the heat balance equation [1, 2]. Here, the velocity and temperature profiles are approximated by relations quadratic in the transverse coordinate with coefficients that depend on the longitudinal coordinate. These are determined from the boundary conditions and the integral relations of boundary layer theory. The relations obtained are used to determine the rate at which a hot rotating ring melts through a block of ice.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 3, pp. 30–34, May–June, 1990.     

The dynamics of relativistic electron fluxes in the near-Earth space in 2001–2005

This paper presents data on relativistic electron fluxes (1.5–3 MeV) measured at altitudes of 360–500 km onboard the CORONAS-F satellite. The monthly average fluxes of these particles in the Earth’s outer radiation belt are shown to greatly increase from August 2001 to September 2003. The monthly average fluxes of relativistic electrons in the Earth’s outer radiation belt in the period from August 2001 to July 2004 are also found to be strongly correlated with the monthly average velocities of the solar wind and values of the Kp-index, with this correlation breaking down after July 2004. This paper discusses the possible reasons for the discovered patterns.     

Absolute, convective, and global instability of a magnetic liquid jet

An infinite or semi-infinite jet of non-conductive magnetic liquid in a uniform longitudinal magnetic field can be absolutely or convectively unstable for different values of the flow parameters. Though the higher field inhibits the absolute instability, this inhibition is maximum at some field intensity. A critical value of the surface tension exists, above which the instability is absolute for any intensity of the field. If the jet has a large but finite length and proper boundary conditions are held at its beginning and end, it is always globally unstable. The unstable global mode is based on a pair of waves that propagate in opposite directions and reflect from one into the other at the flow boundaries.     

Experimental study of high-speed friction on ice

Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 1, pp. 175–177, January–February, 1991.     

Dynamic Mobility of Particles with Thick Double Layers in a Nondilute Suspension

The dynamic mobility of a nondilute suspension of spherical particles is investigated in the case where the thickness of the electrical double layer around each particle is comparable to the particle radius. A formula is obtained for the O(φ) correction in a random suspension of particles with volume fraction φ, involving an integral over the dynamic mobility of a pair of spheres. This formula is then evaluated using both analytical approximations and numerical results previously obtained for the pair mobilities and valid for low surface potentials. The effect of double-layer thickness on the O(φ) coefficient is most pronounced at low frequencies, and lessens once the hydrodynamic penetration depth is smaller than the particle radius. Various approximations are considered that use the O(φ) result to predict the dynamic mobility in concentrated suspensions, and at high frequencies these approximations are shown to give results qualitatively different from those of recent cell models. Copyright 2000 Academic Press.     

The influence of solar flares on the near-Earth space radiation environment in March and April 2013: Possibilities of operational monitoring

This paper deals with the operational analysis of the influence of solar flares, which produced solar cosmic rays, on the near-Earth radiation environment in space during the period from March 1 to April 18, 2013.     

Experimental investigation of high-speed fluid friction

The experimental investigation of the laws of friction at high relative speeds involves difficulties associated with ensuring that the experimental apparatus provides a sufficiently long slide path. In this paper an automated experimental apparatus is described. This makes it possible to study in a compact fashion the laws of fluid friction at speeds of approximately 150 m/sec under widely variable load and external pressure. The experimental relations for the friction moment coefficient for water in the laminar and turbulent regimes are compared with calculations made by the integral relations method of boundary layer theory. The results of series of experimental and theoretical studies of high-speed friction against ice in the developed fusion layer regime are presented. Questions of the effectiveness of using polymer additives to reduce friction at high speeds are considered. The experimental method described can be used to investigate friction problems involving pastes, emulsions, and other rheologically complex continuous media, in which under conditions of high velocity gradients (strain rates) qualitatively new effects are to be expected.Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 3, pp. 74–82, May–June, 1994.