共查询到20条相似文献，搜索用时 156 毫秒
1.
Charged particle motion in magnetoactive plasma with an axially symmetric electrostatic field has been studied. It has been indicated that a difference between drift velocities of electrons and ions leads to a magnetic field disturbance. The equations for stationary magnetic field disturbances stretched along the magnetic field, which can be magnetic ducts for propagation of whistlers, have been obtained. The possibility of formation of such ducts by electrostatic fields from thunderstorm sources, penetrating into the ionosphere, has been estimated. 相似文献
2.
The magnetic field generated by an acoustic wave from a nonstationary point source in an infinite marine medium has been considered.
The spatial-temporal structure of the induced field has been studied in a quasistatic approximation and taking into account
self-induction. The magnetic field in the transient and stationary regimes has been considered. 相似文献
3.
Torsten Bergmark 《Surveys in Geophysics》1984,6(3-4):381-391
A fluxgate magnetometer has been developed at the Geological Survey of Sweden. It measures the field in three orthogonal directions and has sensor elements forming bridges. The instrument can have direct readout in both digital and analogue form with a resolution of 0.1 nT.An instrument of this type has been adopted for stationary recording of geomagnetic elements in digital form. Special attention has been paid to insure good long term stability and high reliability. Experience from routine recording is described. 相似文献
4.
Jyotirmay Mukherjee 《Pure and Applied Geophysics》1970,82(1):11-18
Summary In this paper, the waves propagated in an infinite medium has been considered by disturbances on the surface of a burried spherical source. The disturbances are produced by two types of forces viz. i) Transient normal force, ii) Transient twist applied on the surface of the source. The solutions are obtained in a very simple form. Graphical representations of some numerical solutions has been added at the end of each problem. 相似文献
5.
Summary The present note, as its title implies, is concerned with the investigation of disturbances in an infinite elastic medium containing an initial magnetic field in the axial direction. The equations ofMaxwell, those of elasticity have been effectively made use of to solve the problem. 相似文献
6.
Ballooning disturbances in a finite-pressure plasma in a curvilinear magnetic field are described by the system of coupled equations for the Alfvén and slow magnetosonic modes. In contrast to most previous works that locally analyzed the stability of small-scale disturbances using the dispersion relationship, a global analysis outside a WKB approximation but within a simple cylindrical geometry, when magnetic field lines are circles with constant curvature, is performed in the present work. This model is relatively simple; nevertheless, it has the singularities necessary for the formation of the ballooning mode: field curvature and non-uniform thermal plasma pressure. If the disturbance finite radial extent is taken into account, the instability threshold increases as compared to a WKB approximation. The simplified model used in this work made it possible to consider the pattern of unstable disturbances at arbitrary values of the azimuthal wavenumber (k y ). Azimuthally large-scale disturbances can also be unstable, although the increment increases with decreasing azimuthal scale and reaches saturation when the scales are of the order of the pressure nonuniformity dimension. 相似文献
7.
Summary The author describes a method of determining the size and shape of a gravitating disturbance, treated as a surface-reaching a) vertical cylinder, b) infinite parallelepipedon, when the local Bouguer anomaly field has a) radial symmetry, b) axial symmetry. He introduces the quantity which e. g. serves the purpose of distinguishing very easily between deepseated and shallow disturbances.Presented at the IUGG-Meeting, Helsinki 1960 (IAG, Sec. V). 相似文献
8.
A. V. Mezentsev 《Geomagnetism and Aeronomy》2013,53(3):307-312
The magnetic field behavior in the magnetosheath, when the IMF and the solar wind velocity are almost collinear, has been analyzed based on the perturbation method. Magnetic disturbances are considered against a background of the stationary MHD solar wind flow around the magnetosphere when the magnetic field and the solar wind velocity are strictly collinear. It has been indicated that the angle between the magnetic field and velocity vectors increases considerably in a relatively thin layer near the magnetopause. The angle rise factor profiles have been determined for different distances from the subsolar point. The thickness of the layer, where the angle reaches values of about unity and more, has been estimated. It is important to take this layer into account when the magnetopause stability with respect to Kelvin-Helmholtz waves is analyzed. 相似文献
9.
Ajoy Roy Choudhury 《Pure and Applied Geophysics》1970,80(1):137-146
Summary The propagation of disturbances in cylindrical surfaces of visco-elastic material of general linear type (i) cylinder surrounded by a vacuum (ii) and on an infinite body of same material having a cylindrical cavity, when the surface is subjected to an initially static magnetic field, making use of the electro-magnetic equations of Maxwell, equations of elasticity and the stress-strain relations of the material. 相似文献
10.
B. Yadava 《Pure and Applied Geophysics》1970,78(1):78-85
Summary The transform calculus has been applied to investigate the disturbances in a composite piezoelectric media traversed by a magnetic field. 相似文献
11.
S. L. Ghosh M.Sc. 《Pure and Applied Geophysics》1968,69(1):12-16
Summary In this note the disturbances in an infinite viscoelastic medium ofViogt type with a spherical cavity have been considered. The problem has been solved separately for (1) transient radial forces and (2) transient twist acting on the inner spherical surface of the cavity. Exact solutions have been obtained in both cases. 相似文献
12.
N. I. Izhovkina 《Geomagnetism and Aeronomy》2013,53(3):329-336
A vortex structure renders additional stability to plasma irregularities stretched along magnetic field lines. Plasma irregularities extended over several tens of kilometers are registered with rocket and satellite equipment in the topside ionosphere. The registered scale of irregularities depends on the spatial and time resolution of the equipment used. Irregular structures were registered in the ionosphere during experiments with barium clouds and jets, when a plasma irregularity separated into strata extended over several meters and several kilometers across the geomagnetic field. It has been indicated that plasma vortices can be generated in an unstable plasma in a situation when its quasi-neutrality is disturbed. Local geomagnetic field disturbances will be caused by the appearance of a proper vortex magnetic field. Plasma vortices can interact in an inhomogeneous plasma with an unstable electron component. Such interactions are related to the transformation of the phase volume of free electrostatic oscillations in the frequency-wave vector space. 相似文献
13.
M. C. Wadhawan 《Pure and Applied Geophysics》1973,102(1):37-50
Summary Using the generalised dynamical theory of thermoelasticity, thermoelastic problem for an isotropic infinite circular cylinder has been solved by approximate techniques. A two dimensional harmonic problem for a cylinder has also been considered and small amplitude vibrations of the circular cylinder have been studied further. 相似文献
14.
Dilip K. Sinha 《Pure and Applied Geophysics》1965,60(1):18-22
Summary The method of operational calculus has been used to deal with the disturbances in an elastic medium traversed by a magnetic field. 相似文献
15.
Nongyrotropic (gyrophase bunched) ion distributions in a magnetoplasma are studied by analytical methods and by two-dimensional hybrid code simulations. Nongyrotropy may not occur in a plasma being simultaneously homogeneous, stationary, and solenoidal in phase space. A detailed study is performed for a homogeneous and stationary plasma with sources and sinks in phase space. The analytical investigation cast in the framework of linearized Maxwell-Vlasov theory yields a coupling of low-frequency left-handed, right-handed, and longitudinal modes. Nongyrotropic ion distributions are unstable; they excite left-handed waves. The growth rate is comparable to that of the ion ring instability. The hybrid code simulation study confirms the expected propagation direction parallel to the background magnetic field. Three diffusion processes are studied: arc lengthening, arc broadening, and arc radius decreasing corresponding to particle energy diffusion. The characteristic diffusion time-scales are found to be of the order of 101 wave cycles. 相似文献
16.
Large-scale disturbances in the ionospheric plasma, caused by the spacecraft launches from the Baikonur site, have been analyzed based on the incoherent scatter radar measurements. The altitude-time dependences of the main plasma parameters (electron density and electron and ion temperatures at altitudes of ～100–600 km) have been analyzed. It has been indicated that spacecraft launches and flights are accompanied by the generation of wave-like disturbances in all considered parameters. It has been obtained that the relative amplitudes of these wave-like disturbances were usually 0.03–0.10, and the variation period was 20–60 min. The variations were shifted in phase relative to each other. The propagation velocities of wave-like disturbances were ～0.5–0.6 and 1.5–2 km/s. The up-to-date methods of spectral analysis, including the wavelet analysis, were used to estimate the parameters of the wave-like disturbances. 相似文献
17.
Summary The compressional angle of isallo stress theory for the case of a cylindrical (circular and elliptic) and spherical subsurface inhomogeneity, assuming that the conjugate fracture surfaces are inclined at a Mohr angle of 30° toward the largest compression, has been calculated. The solution for a spherical and cylindrical inclusion in an infinite medium subject to a uniform stress field (at infinity) were taken as the basis for the stress analysis. The stress angle was then calculated for the mentioned types of inclusions. 相似文献
18.
P. Roy 《Pure and Applied Geophysics》1970,82(1):29-33
Summary The propagation of longitudinal disturbances in a viscoelastic solid of Reiss type subjected to a magnetic field has been obtained in the present note. 相似文献
19.
N. Bhanja 《Pure and Applied Geophysics》1972,101(1):38-42
Summary The investigation of the stress-components in an infinite, plate of isotropic homogeneous material with a circular hole has been made by applying Cosserat's theory of couple-stresses. The plate is acted on by two equal concentrated forces at the diametrically opposite points of the inner boundary. 相似文献
20.
Kuo-Chin Hsu Kuan-Chih Chen 《Stochastic Environmental Research and Risk Assessment (SERRA)》2010,24(7):1053-1065
This paper proposes a multiscale flow and transport model which can be used in three-dimensional fractal random fields. The
fractal random field effectively describes a field with a high degree of variability to satisfy the one-point statistics of
Levy-stable distribution and the two-point statistics of fractional Levy motion (fLm). To overcome the difficulty of using
infinite variance of Levy-stable distribution and to provide the physical meaning of a finite domain in real space, truncated
power variograms are utilized for the fLm fields. The fLm model is general in the sense that both stationary and commonly
used fractional Brownian motion (fBm) models are its special cases. When the upper cutoff of the truncated power variogram
is close to the lower cutoff, the stationary model is well approximated. The commonly used fBm model is recovered when the
Levy index of fLm is 2. Flow and solute transport were analyzed using the first-order perturbation method. Mean velocity,
velocity covariance, and effective hydraulic conductivity in a three-dimensional fractal random field were derived. Analytical
results for particle displacement covariance and macrodispersion coefficients are also presented. The results show that the
plume in an fLm field moves slower at early time and has more significant long-tailing behavior at late time than in fBm or
stationary exponential fields. The proposed fractal transport model has broader applications than those of stationary and
fBm models. Flow and solute transport can be simulated for various scenarios by adjusting the Levy index and cutoffs of fLm
to yield more accurate modeling results. 相似文献