On the structure of the middle Jovian magnetosphere

A model of the plasma distribution in the middle Jovian magnetosphere is considered. The distribution of the background plasma along the magnetic lines of force under the action of the centrifugal force and the force of gravity is analyzed in the framework of the diffusive equilibrium, taking into account the finite angle between the magnetic and rotational axes. It is shown that the dense structures of the background plasma have the form of a warped sheet located between the magnetic and centrifugal equators, and of two mirror symmetrical petals in the vicinity of the polar cusps. The hydrodynamic stability of the dense plasma sheet, formed under the action of the centrifugal force, is studied. The steady state radial plasma distribution at the threshold of the instability with respect to the small-scale MHD perturbations is determined. The finite conductivity of the Jovian ionosphere is taken into account. The influences of the longitudinal inhomogeneity of the perturbations, the finite ion Larmor radius, and the curvature of the magnetic field lines on the threshold of the instability are estimated. Some aspects of the formation of the energetic particle distribution in the middle Jovian magnetosphere are considered. The suggested model shows reliable agreement with the known experimental data and is also useful in describing the background plasma distribution in the magnetospheres of Neptune and Uranus.Institute of Applied Physics, Russian Academy of Sciences, Nizhny Novgorod. Traslated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 37, No. 5, pp. 580–595, May, 1994.     

Effect of limiting polarization in the Jovian inner magnetosphere

Jovian decameter emission is known to exhibit almost total polarization. We consider the elliptical polarization to be a consequence of linear-mode coupling in the Jovian magnetosphere outside the source region. We determine conditions of emission propagation along the ray path that are necessary for self-consistent explanatation of the polarization observations and show that the ellipticity (axial ratio of the polarization ellipse) is determined by the magnetospheric plasma density n_e in a small region a distance of about half the Jovian radius from the radiation source. The plasma density in the region is quite low, n_e<0.4 cm⁻³, and the geometrical-optics approximation of emssion propagation in front of the region converts to the vacuum approximation behind it. The latter means that the linear-mode coupling in the Jovian inner magnetosphere is manifested as the effect of limiting polarization. Sources of decameter emission emitting at different frequencies f are located at heights corresponding to gyrofrequency levels f _Be ≅f and at magnetic-force lines that belong to L-shells passing through the satellite Io. The location of the transitional region in the Jovian magnetosphere varies depending on the emission frequency and the time. For each given decameter radio emission storm occupying some region in frequencytime space, we have a number of transitional regions located in a certain region of the Jovian magnetosphere—the interaction region of the magnetosphere (IRM) for the given emission storm. The distribution of magnetospheric plasma in an IRM is found from data of observations of the polarization ellipiicity of the given decameter radio emission storm. By matching the calculated ellipticity of emission with the observed ellipticity at every point of frequency-time space of the emission dynamic spectrum one finds a recurrent relation between the local values of the magnetospheric plasma density N_c and the planetary magnetic field B in the IRM, which allows evaluation of the distribution of plasma density if a definite model of the Jovian magnetic field has been adopted. Institute of Applied Physics, Russian Academy of Sciences, Nizhny Novgorod, Russia; Space Research Institute, Austrian Academy of Sciences, Austria. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 41, No. 2, pp. 177–193, February, 1998.     

Collisionless magnetic reconnection in the magnetosphere

Magnetic reconnection underlies the physical mechanism of explosive phenomena in the solar atmosphere and planetary magnetospheres, where plasma is usually collisionless. In the standard model of collisionless magnetic reconnection, the diffusion region consists of two substructures: an electron diffusion region is embedded in an ion diffusion region, in which their scales are based on the electron and ion inertial lengths. In the ion diffusion region, ions are unfrozen in the magnetic fields while electrons are magnetized. The resulted Hall effect from the different motions between ions and electrons leads to the production of the in-plane currents, and then generates the quadrupolar structure of out-of-plane magnetic field. In the electron diffusion region, even electrons become unfrozen in the magnetic fields, and the reconnection electric field is contributed by the off-diagonal electron pressure terms in the generalized Ohm's law. The reconnection rate is insensitive to the specific mechanism to break the frozen-in condition, and is on the order of 0.1. In recent years, the launching of Cluster, THEMIS, MMS, and other spacecraft has provided us opportunities to study collisionless magnetic reconnection in the Earth's magnetosphere, and to verify and extend more insights on the standard model of collisionless magnetic reconnection. In this paper, we will review what we have learned beyond the standard model with the help of observations from these spacecraft as well as kinetic simulations.     

Structure and magnetic field of periodic permanent magnetic focusing system with open magnetic rings

The magnetic field along the central axis for an axially magnetized permanent magnetic ring was investigated by analytical and finite element methods. For open magnetic rings, both calculated and measured results show that the existence of the radial magnetic field creates a remarkable cosine distribution field along the central axis. A new structure of periodic permanent magnet focusing system with open magnetic rings is proposed. The structure provides a satisfactory magnetic field with a stable peak value of 120 mT for a traveling wave tube system.     

Nonlinear model for coherent electric field structures in the magnetosphere

A new pseudo-three-dimensional electron hole in a magnetized plasma is possible when the low-frequency ion dynamics is taken into account. The newly found nonlinear Bernstein-Greene-Kruskal stationary solution, whose parallel phase velocity ranges between almost zero and the electron thermal speed, has the form of a cylinder that is tilted relative to the magnetic field. These structures are interpreted as three-dimensional electron holes coupled with hydrodynamic vortices, and provide a possible theoretical explanation for the POLAR and FAST satellite observations of coherent structures characterized by bipolar spikes of the parallel electric field and large perpendicular ion kinetic energies.     

Structure of the intersubband collective excitations in quasi-two-dimensional systems in a magnetic field

The spectrum of intersubband collective spin-and charge-density excitations is calculated for a system of quasi-two-dimensional electrons with ν≤10 (ν is the filling factor) in a magnetic field. The transitions both without changing the Landau level and with its change (Bernstein modes) are considered. All excitations are shown to have a multimode structure, the number of modes being determined by the filling factor. The dispersion and interaction of small-quasimomentum collective excitations are also considered. The possibility of observing the multimode structure is predicted.     

斜磁场作用下的射频等离子体平板鞘层结构

建立一个一维坐标空间、三维速度空间的斜磁场作用下的射频等离子体平板鞘层模型，讨论了磁场对射频鞘层结构及其参数特性的影响.研究结果表明：磁场对鞘层结构有不可忽略的影响，特别是能够使鞘层边界附近的离子速度分布和密度分布产生明显的变化.此外，虽然磁场不能改变离子总的能量密度分布，却能改变离子的运动状态，并同时影响着基板上离子在各个方向上的能量分布和入射偏移角度. 关键词： 射频 鞘层 磁场     

Structure of the magnetic field perturbations of a low-frequency dipole by a metallic sphere

The potentials of the magnetic field of a low-frequency magnetic dipole reflected by a sphere are analyzed. It is shown that for short ranges between the dipole and the sphere this field can be described by one potential, where the field is equivalent to the field of a system of dipoles and charges.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 73–77, March, 1976.     

Structure and dynamic properties of the twisted magnetic domain wall in an electric field

The structure of the domain wall in a magnetically uniaxial ferromagnetic film placed in an external electric field has been studied. It has been shown that the domain wall has a complex twisted structure whose characteristics (thickness, profile, and limit velocity of steady motion) depend on the film thickness, quality factor, and external electric field. The effect of the electric field on the domain wall is caused by inhomogeneous magnetoelectric coupling taking place in domain walls with a twisted structure.     

Structure and electrical properties of polyaniline synthesized in presence of low magnetic field

Chemical polymerization of aniline is carried out in the presence of low magnetic field (1 kG and 2 kG). The impact of application of magnetic field externally during polymerization increases the electrical conductivity by two orders of magnitude. This enhanced electrical conductivity depends on ordering of polymer chain, structure, molecular weight, magnetic susceptibility, and thermal characteristics of polyaniline which has been studied and reported.     

The magnetic field of the planets

Summary The predictions of a model of the magnetic field of rotating bodies are compared with the results of observations of the magnetic fields of the planets. Further observations of the Mars and the lumar magnetic fields are suggested.

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Riassunto Si confrontano le previsioni di un modello del campo magnetico di un corpo rotante con i risultati di osservazioni dei campi magnetici dei pianeti. Si suggeriscono ulteriori osservazioni di campi magnetici di Marte e della Luna.

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Резюме Предсказания модели магнитного поля вращающихся тел сравниваются с результатами наблюдений магнтных полей планет. Предлагаются дальнейшие исследования магнитных полей Марса и Луны.

     

Structure of the Abrikosov vortex lattice in a thin superconducting film in a parallel magnetic field

The structure of a vortex lattice in thin (d<λ, where d is the film thickness and λ is the London penetration depth) superconducting films is investigated in a magnetic field parallel to the film surface. It is shown that the stable configuration has the form of discrete vortex rows whose number changes discretely with an increase in the applied magnetic field. The entry fields H _c1 ^(N) (d) for vortex rows are calculated for N=1, 2. It is shown that the structural transition in the vortex ensemble is a second-order phase transition. A simpler method (as compared to the Monte Carlo technique) is proposed for calculating the vortex lattice parameters.     

Structure factor of ferrofluids with chain aggregates: Influence of an external magnetic field

In this paper we present the structure factor of ferrofluid with chain aggregates under the influence of an externally applied magnetic field. On the basis of the equilibrium chains distribution the structure factor is calculated as Fourier transform of the radial distribution function. An extensive comparison of the theoretical model to the results of computer simulations showed a qualitative agreement of the data. The existence of the chains leads to strong anisotropy of the structure factor for the cases parallel and perpendicular to the external magnetic field.     

Electrohydrodynamics of the pulsar magnetosphere

The dispersion relations for weak waves in a cold, charge-separated plasma (due to a strong rotating magnetic field) show that radio waves, and even low frequency waves can propagate through a (one-component) pulsar magnetosphere.     

Breakdown in the transverse magnetic field

The breakdown between coaxial cylindrical electrodes in the homogeneous axial magnetic field in the pressure range around the Paschen minimum is studied. On the right of this minimum the breakdown voltage is not practically influenced by a weak magnetic field. On the left of this minimum the breakdown U-B curves can be divided into two branches: the upper ones can be approximated by the magnetron cut-off parabola, the lower ones correspond qualitatively in some cases to the second solution of the equation for breakdown in the inhomogeneous electric field corrected with respect to the losses of electrons caused by recapturing on the cathode.     

Conductance distribution in the magnetic field

Using a modification of the Shapiro scaling approach, we derive the distribution of conductance in the magnetic field applicable in the vicinity of the Anderson transition. This distribution is described by the same equations as in the absence of a field. Variation of the magnetic field does not lead to any qualitative effects in the conductance distribution and only changes its quantitative characteristics, moving a position of the system in the three-parameter space. In contrast to the original Shapiro approach, the evolution equation for quasi-1D systems is established from the generalised DMPK equation, and not by a simple analogy with one-dimensional systems; as a result, the whole approach became more rigorous and accurate.