Equilibrium of toroidal configurations

A solution of the equilibrium equation for plasma has been found up to any degree of nonlinearity in form of double series. Applications are presented for the zero- and first-order approximation.     

Influence of a dipole magnetic field on the topology of toroidal magnetic configurations around a gravitating body

The topological structure of the toroidal magnetic field, which is affected by a dipole magnetic field, is studied. It is shown, that a dipole magnetic field is able to split the initial toroidal configuration into two toroids and, at a certain critical value of the magnetic dipole, can completely destroy the toroidal configuration. The dependence of the total mass excess on the dipole magnetic field is found.     

The study of toroidal magnetic configurations in a spherically symmetric gravitational field with applications to coronal loops and transients

One procedure for solving MHD equations is to search for a solution in an area that is restricted by boundary surfaces. This procedure requires the magnetic field to be truncated on the boundary. As a result, boundary current sheets appear. This approach is certainly acceptable for laboratory plasma experiments in which these surfaces are made of metal. For astrophysically relevant plasma, an alternative approach has been formulated by the author. We require the total magnetic energy,W, to be finite and, simultaneously, the magnetic fieldB to be continuous. The proposed approach leads to an eigenvalue problem that is treated analytically. The complete set of exact MHD solutions with multi-toroidal structure is obtained. These solutions are applied to coronal loops and transients, using the similarity assumption for time-dependent solutions.The derived pressure and density excess distributions are discussed. The estimation of the total mass excess, as well as the minimum value of the magnetic field intensity, is demonstrated. An indirect way of obtaining magnetic field measurements for transients, based on the developed model, is proposed.     

Magneto-dipole configurations in general relativity

The solution of the system of Maxwell-Einstein equations, which determines the external gravitational and electromagnetic fields of magneto-dipole configurations, has been obtained to a quadratic approximation of magnetic momentum.     

Seasonal variations in the north toroidal sporadic meteor source

Abstract— Determining the origins of the sporadic meteoroid sources helps determine their current properties. We have analyzed four years of orbital radar data, looking at how the rates, radiants, and orbits of meteoroids in the north toroidal sporadic source change throughout the year. Twelve broad radiant concentrations, separated in either time or radiant location, are identified. Six are broad distributions associated with more focused shower activity, and six are not associated with major showers. Four of the six concentrations not associated with showers have been named Toroidal, Toroidal A, Toroidal B, and Toroidal C, because of their constant location at the north toroidal centre. The other two, which appear close to the north toroidal source and drift toward the helion and antihelion sources respectively, have been named the Helion Arc and the Antihelion Arc. The twelve radiant concentrations generally last for more than ten degrees solar longitude, and those which may have a single parent are likely composed of orbitally evolved material.     

Drift Kelvin-Helmholtz instabilities in space plasmas

We implement a complex-plane strategy and a multiple partition technique to the computation of polytropic models distorted by very strong and very rapid differential rotation. We also verify with our numerical results a heuristic relation between stability and virial theorem.     

Seven-body central configurations: a family of central configurations in the spatial seven-body problem

The main result of this paper is the existence of a new family of central configurations in the Newtonian spatial seven-body problem. This family is unusual in that it is a simplex stacked central configuration, i.e the bodies are arranged as concentric three and two dimensional simplexes.      

The dynamics of a toroidal magnetic ring

Solving the nonlinear partial differential equations of magnetohydrodynamics numerically, we examine (1) the time development of a purely toroidal magnetic field (a magnetic ring) and (2) the interaction of a magnetic ring with a poloidal magnetic field. Axisymmetry and incompressibility are assumed. Parameters are chosen to correspond to photospheric conditions. In case (1), the magnetic ring contracts to the axis and then splits in two with one ring travelling up along the axis and the other down. In case (2), a large toroidal velocity field is generated which has opposite direction of flow above and below the magnetic ring. The magnetic and flow patterns of case (2) may persist with little change for a relatively long time. We conjecture that toroidal magnetic fields may be involved in the bright rings of sunspots or in the dynamics of spicules.The National Center for Atmospheric Research is sponsored by the National Science Foundation.     

Chaos-induced resistivity in different magnetic configurations

It is widely believed that magnetic reconnection plays an important role in various eruptive phenomena of space and astrophysical plasmas.The mechanism of anomalous resistivity,however,has been an open and unsolved problem.The chaos-induced resistivity proposed by Yoshida et al.is one of possible mechanisms for anomalous resistivity.By use of the test particle simulation,the present work studies the chaos-induced resistivity for different configurations of reconnection magnetic fields and its distribution in different chaos regions of reconnection current sheets.The results show that the chaos-induced resistivity can be 6-7 orders of magnitude higher than the classical Spitzer resistivity in the X-type chaos regions and 5 orders of magnitude in the O-type chaos regions.Moreover,in the X-type chaos regions the chaosinduced resistivity of the magnetized case is higher by a factor of 2 to 3 times than that of the unmagnetized case,but in the O-type chaos regions the chaos-induced resistivity of the magnetized case is close to or lower than that of the unmagnetized case.The present work is helpful to the understanding of the dynamics of reconnection current sheets,especially of the generation mechanism of the anomalous resistivity of collisionless reconnection regions.     

Particle dynamics in reconnection field configurations

Trajectories of test particles are studied numerically in two types of reconnection magnetic field configurations, a single X-line magnetic field configuration and a tearing magnetic field configuration. Both adiabatic and nonadiabatic motions are examined, with special emphasis on net energy gain and time spent in the neutral line regions. They spend typically one characteristic gyroperiod in the X-line region and are ejected predominantly along field lines in the vicinity of the separatrix. Both adiabatic and nonadiabatic test particles in the tearing-type field configuration are channelled into and accelerated along the O-line region. It may be inferred from these test particle results that particle energizations are significant along the O-line region, but not along the X-line region. These results are in qualitative agreement with those obtained by a self-consistent particle simulation.     

The central drop configurations

This paper deals with the investigation of central configurations consisting of a point body, a homogeneous sphere and some drops of homogeneous ideal fluid. The existence of such central configurations, as well as the stability of the drops in linear approximation, has been proved by using the virial method (Chandrasekhar, 1969).     

Drift Scanning from Ground and in Space

The drift scanning technique offers, in principle, a simple and efficientmethod for imaging wide regions of the sky with intrinsic high astrometricaccuracy. Its performance is analyzed in two distinct environments, namelyfrom a small class ground based telescope and a spaceborne interferometer. Inparticular, the study is referred to the proposed ESA cornerstone missionGAIA (Global Astrometric Interferometer for Astrophysics).The constant clock rate of a CCD, due to the declination dependentsidereal speed variation, results in a systematic image smearing, whichlimits the positional accuracy. Moreover, the readout timing accuracyprovides an additional random noise corresponding to a drift speed jitter.Stability requirements on the order of 10-6 or better have to be fulfilledfor the space option.Both effects can be addressed by proper system design; provisionalimplementation strategies are discussed for both applications.     

Additional results for unstable stratified toroidal magnetic fields in stars

General conditions for adiabatic instability of weak axisymmetric toroidal magnetic fields are obtained. In particular all fields which haveH =0 and H ² />0 simultaneously are unstable. This includes all fields which exist near to the axis of symmetry and, indeed, any without an infinite current density anywhere. A detailed discussion is given of fields with an angular dependenceH ² |P (cos )|. These fields are dynamically unstable with respect to both axisymmetric and non-axisymmetric perturbations for all values of the azimuthal wave number |m|. The maximum growth rates are independent ofm and they are largest for the fields that are defined in the regions closest to the polar axis.     

Vertically self-gravitating ADAFs in the presence of toroidal magnetic field

Force due to the self-gravity of the disc in the vertical direction is considered to study its possible effects on the structure of a magnetized advection-dominated accretion disc. We present steady-sate self similar solutions for the dynamical structure of such a type of the accretion flows. Our solutions imply reduced thickness of the disc because of the self-gravity. It also imply that the thickness of the disc will increase by adding the magnetic field strength.     

Generation of a toroidal magnetic field in rotating neutron stars

The electromagnetic properties of neutron stars (pulsars) are studied. It is shown that taking the presence of two angular rotation velocities of the components of neutron stars and the first corrections to the general theory of relativity into account in the equations of hydrodynamic equilibrium for the plasma and in Maxwell’s equations leads to the generation of toroidal magnetic fields in the depths of a neutron star. __________ Translated from Astrofizika, Vol. 49, No. 1, pp. 97–101 (February 2006).     

Equilibrium structure of polytropes with toroidal magnetic fields

Structure equations for the equilibrium of the gaseous polytropes with toroidal magnetic fields are solved numerically for two values of polytropic indexn-1.5 and 3, using a variant of Stoeckly's method. In addition to the structure parameters frequencies of the characteristic modes of oscillation are calculated. The results are considerably different from the values obtained by Anand for weak toroidal fields.     

Solar Drift Pair Bursts in the Decameter Range

The results of observations of solar decametric drift pair bursts are presented. These observations were carried out during a Type III burst storm on July 11–21, 2002, with the decameter radio telescope UTR-2, equipped with new back-end facilities. High time and frequency resolution of the back-end allowed us to obtain new information about the structure and properties of these bursts. The statistical analysis of more than 700 bursts observed on 13–15 July was performed separately for “forward” and “reverse” drift pair bursts. Such an extensive amount of these kind of bursts has never been processed before. It should be pointed out that “forward” and “reverse” drift pair bursts have a set of similar parameters, such as time delay between the burst elements, duration of an element, and instant bandwidth of an element. Nevertheless some of their parameters are different. So, the absolute average value of frequency drift rate for “forward” bursts is 0.8 MHz s⁻¹, while for “reverse” ones it is 2 MHz s⁻¹. The obtained functional dependencies “drift rate vs. frequency” and “flux density vs. frequency” were found to be different from the current knowledge. We also report about the observation of unusual variants of drift pairs, in particular, of “hook” bursts and bursts with fine time and frequency structure. A possible mechanism of drift pairs generation is proposed, according to which this emission may originate from the interaction of Langmuir waves with the magnetosonic waves having equal phase and group velocities.