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1.
An extended current sheet characterized by two peculiarities was formed in a configuration with opposite magnetic fields in a laboratory plasma on a -pinch device. First, development of the small scale turbulence leads to abnormal low sheet conductivity, through-sheet plasma diffusion and establishes the sheet thickness an order greater than the skin thicknessc/ pe ( pe is electron plasma frequency). Second, there develops and quickly stabilizes in a sheet the magnetic force line reconnection. As a result, a stable neutral sheet has the complicated structure of a magnetic field, including closed magnetic loops elongated along the axis of the system. The neutral sheet plasma becomes intensively heated, probably due to ion-sound turbulence, while a group of accelerated electrons, which on the energy spectrum lead to a plateau formation, are observed. The absence of any predominant direction is a typical feature for the motion of accelerated particles. The experimental data, obtained over a broad range of plasma densities and magnetic field values typical for the solar atmosphere, show that the antiparallel magnetic field turbulent dissipation could play an important role in the mechanism of solar energy release. The parameters of accelerated particles (energy 4–12 keV, the energy content being 10–1–102 of all the energy dissipated in a sheet) agree nicely with the data of astrophysical observations.  相似文献   

2.
Explorer 34 (Imp 4) 2.56 s magnetic data during 131 traversals of the tail current sheet are presented along with simultaneous 2.5 min auroral electrojet indices AE and AL. The normal magnetic field,B , satellite crossing times and positions are tabulated for these 131 crossings.B is defined in the center of the sheet: it is the vector magnetic field at the time of field minimum during the crossing (B x component changes sign). It is remarkable that the only normal components too large in magnitude to be classified as fine structure occur near the time of onset of an AE event. Cases are discussed where the normal component, defined near the plasma sheet edges, has the opposite sign compared to the normal component defined at the sheet center. For quiet times, the current sheet may be only about 1000 km thick within a 3R e (Earth-radii) plasma sheet, and may carry some 10–15% of the total tail current.  相似文献   

3.
A simple self-consistent model of a high-temperature turbulent current sheet (HTCS) is considered. The anomalous character of plasma conductivity in a sheet is assumed to be due to gradient instabilities. The possibility of a low threshold of their excitation is demonstrated by an example of temperature-drift instability.Application of the HTCS model to the hot or main phase of a solar flare is discussed. The model consistently explains many observed properties of this phase.  相似文献   

4.
Using the results of numerical simulations of the solar atmospheric response to heating by nonthermal electron beams during solar flares, we have calculated the spatial and temporal evolution of both (i) the direct (beam-target) nonthermal bremsstrahlung and (ii) the thermal bremsstrahlung arising from the hot plasma energized by the electron beam. Typically, we find that below a certain cross-over energy E *, the emission is dominated by the thermal component, while at higher energies the direct bremsstrahlung component becomes more important. This cross-over energy is dependent on the position within the loop, generally increasing with height.We have also investigated the dependence of the cross-over energy E * on the parameters of the electron energy input. At the time of peak electron flux injection the cross-over energy E * can, for plausible parameters, be as high as 52 keV at the top 1 pixel, and as low as 16 keV at the bottom 1 pixel. We conclude that a possible reassessment of SMM HXIS data as an indicator of the thermal or nonthermal character of the primary energy release (based primarily on the geometric properties of the hard X-ray source) is required. Our results also point to the minimum photon energy that future instruments should observe (where practical, giving due consideration to detector sensitivity) in order to be sure that, in the context of the thick-target interpretation, the nonthermal component is not swamped by the self-consistent thermal counterpart created by the beam heating.  相似文献   

5.
It is found that the relationship between the potential energy and the moment of the inertia independent of the radial mass distribution obtained earlier for the sphere also holds in the case of the ellipsoidal mass distribution for the ellipsoid of rotation.The possibility of application of the energy virial relations for solution of the evolutionary problems of the gravitating gaseous sphere, with the help of the relationship found earlier, is demonstrated. The physical conditions on the gaseous sphere boundary are introduced. The existence of two branches of evolution, the proton one and the electron one, is established. The problem of the gravitational contraction velocity during sphere evolution is solved. The relationship between the boundary temperature and the gaseous sphere radius as well as between the luminosity and the body mass is obtained. Some limiting relations for the final stage of the gaseous sphere evolution are found.
, , , . . . — . . , . .
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6.
Simple self-consistent models for non-neutral current sheets are considered. Characteristics of high-temperature turbulent current sheets (HTCS) with a small transverse component of magnetic field are determined for conditions in the solar corona. The energy output of such an HTCS is much larger than that of a neutral sheet. This makes it possible to consider the HTCS as an energy source not only in long-lived X-ray loops but also in flaring loops during the not or main phase of a flare. In this case, the magnetic reconnection velocity agrees with the observed velocity of the loop rise. Thus, these phenomena can be interpreted as a result of magnetic reconnection, for example, between new flux emerging from under the photosphere and an old magnetic field.The role of a longitudinal magnetic field in a current sheet is less important for HTCS. As a result of the compression of a longitudinal field, there appears an electric current circulating around the sheet. This current may induce strong Joule heating, if the compression is large. This additional heating is realized because of the annihilation of the main component, not the longitudinal component of magnetic field. The effect is small for HTCS, but may be significant for preflare current sheets.  相似文献   

7.
We consider the system of neutrino-antineutrino – plasma taking into account theirweak Fermi interaction, when the density of neutrinos andthe plasma particles are rather high and their collective interactionplays a vital role. New fluid instabilities driven by strong neutrino flux in aplasma are observed. It is shown that a bunch of neutrinos, drifting witha constant velocity across a homogeneous plasma, can also induce emission oflower energy neutrinos due to scattering, i.e. the decay of a heavy neutrinoH into a heavy and a light neutrino L(HHL) in a plasma. Furthermore we find thatthe neutrino production in stars does not lead in general to energy lossesfrom the neutron stars.  相似文献   

8.
An analysis of the effects of Hall current on hydromagnetic free-convective flow through a porous medium bounded by a vertical plate is theoretically investigated when a strong magnetic field is imposed in a direction which is perpendicular to the free stream and makes an angle to the vertical direction. The influence of Hall currents on the flow is studied for various values of .Nomenclature c p specific heat at constant pressure - e electrical charge - E Eckert number - E electrical field intensity - g acceleration due to gravity - G Grashof number - H 0 applied magnetic field - H magnetic field intensity - (j x , j y , j z ) components of current densityJ - J current density - K permeability of porous medium - M magnetic parameter - m Hall parameter - n e electron number density - P Prandtl number - q velocity vector - (T, T w , T ) temperature - t time - (u, v, w) components of the velocity vectorq - U 0 uniform velocity - v 0 suction velocity - (x, y, z) Cartesian coordinates Greek Symbols angle - coefficient of volume expansion - e cyclotron frequency - frequency - dimensionless temperature - thermal conductivity - coefficient of viscosity - magnetic permeability - kinematic viscosity - mass density of fluid - e charge density - electrical conductivity - e electron collision time  相似文献   

9.
J. J. Aly 《Solar physics》1989,120(1):19-48
Using a simple model in which the corona is represented by the half-space domain = {z > 0} and the photosphere by the boundary plane = {z = 0}, we discuss some important aspects of the general problem of the reconstruction of the magnetic field B in a small isolated coronal region from the values of the vector B¦ measured by a magnetograph over its whole basis. Assuming B to be force-free in : (i) we derive a series of relations which must be necessarily satisfied by the boundary field B¦ , and then by the magnetograph data if the force-free assumption is actually correct; (ii) we show how to extract directly from the measured B¦ some useful informations about the energy of B in and the topological structure of its field lines; (iii) we present a critical discussion of the two methods which have been proposed so far for computing effectively B in from B¦ .  相似文献   

10.
A limiting case of the problem of three bodies (m 0,m 1,m 2) is considered. The distance between the bodiesm 0 andm 1 is assumed to be much less than that between their barycenter and the bodym 2 so that one may use Hill's approximation for the potential of interaction between the bodiesm 1 andm 2. In the absence of resonant relations the potential, double-averaged by the mean longitudes ofm 1 andm 2, describes the secular evolution of the orbits in the first approximation of the perturbation theory.As Harrington has shown, this problem is integrable. In the present paper a qualitative investigation of the evolution of the orbits and comparison with the analogous case in the restricted problem are carried out.The set of initial data is found, for which a collision between the bodiesm 0 andm 1 takes place.The region of the parameters of the problem is determined, for which plane retrograde motion is unstable.In a special example the results of approximate analysis are compared with those of numerical integration of the exact equations of the three body problem.
m 0,m 1,m 2. , m 0 m 1. m 2, m 1 m 2 m 1 m 2 . , . . , m 0 m 1. , . .
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11.
An essential part in the mechanics under study is taking into consideration the effect of motions of the Universe objects upon that of an individual one surrounded by them including those infinitely far from it. Only macro-objects of the Universe are meant here.
Zusammenfassung Ein wesentlicher Bestandteil der Mechanik unter unserer Betrachtung ist die Berechnung des Einflusses auf die Bewegung eines individuellen Objektes von Bewegungen der Universum Objekte die es umringen einschließlich jene Objekte, die unendlich entfernt sind. Nur Makroobjekte des Weltalles sind in der Absicht dabei.
, . .
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12.
Since the average relation between the angular momentaP and the massesM of galaxies can be represented by a power lawPM , we can define a relative angular momentum =P/M (or a constant timeP/M ). For a random motion picture within protogalaxies, should follow a Maxwellian distribution and consequently the dispersion of log should be 0.210.For the reasonable range of ( to 2), the limited sample of galaxies with known dynamical parameters gives between and 1 times the Maxwellian value. For the plausible special case =2 the reciprocal of the maximum rotational velocityv m is already a measure of and the larger sample ofv m-values not only yields the Maxwellian but, moreover, shows the shape of the distribution.
PM , =constP/M . , (lg )=0.210. 7/42, . =2 v m- .
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13.
Orbital stability of quasiperiodic motions in the many dimensional autonomic hamiltonian systems is considered. Studied motions are supposed to be not far from equilibrium, the number of their basic frequencies may be not equal to the number of degrees of freedom, and the procedure of their construction is supposed to be converged. The stability problem is solved in the strict nonlinear mode.Obtained results are used in the stability investigation of small plane motions near the lagrangian solutions of the three-dimensional circular restricted three-body problem. The values of parameters for which the plane motions are unstable have been found.
. , , . . , . , .
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14.
The interaction processes governing the penetration of the interstellar gas into the solar neighbourhood are re-examined — as well as photo-ionization and charge-exchange processes, proton elastic collisions and electron ionizations help reduce the nearby gas densities. The total destruction rate varies little during the solar cycle, by perhaps 10%. Particle heating, particularly via the elastic collisions, determines the gas characteristics in the gravitationally focussed tail—enhanced H-density is prevented, while the He-tail is effectively hotter than 103 K.Termination of the solar wind is rediscussed in the light of both electron heating and the stronger gas/plasma interaction. The spiral interplanetary field is taken to break up and the subsonic plasma flow to be controlled by the pressure of slowly cooling electrons. The terminating collisionless shock is then, if it exists at all, very weak (M 1<1.4), subcritical, and energetically unimportant. Cosmic rays are little affected by this sonic transition, but at least the electron component should be modulated by plasma turbulence throughout the ionizing flow.
. , . , . . .
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15.
, , , , ,S , , , S Mg. , . , . , ( , ..). B5 B0; (<1%).  相似文献   

16.
(, 1969). ( ), ( ), , , . , (=), , , .. , . , , - ( ), ( ). , .
This paper is a continuation and a generalization of one published earlier (Duboshin, 1969): it discusses the problem whether there exist the Lagrangian and the Eulerian solutions of the generalized three-body (material points) problem. Every point in this generalized problem acts on another, one with a force (attractive or repulsive) directed along the straight line passing through these points, and in an arbitrary manner depending on time, mutual distance and its derivatives, the first and the second. Here, generally speaking, the third axiom of dynamics (law of action and reaction) is not presupposed as fulfilled, that is, it is supposed that every two material points interact in a different way.This most general assumption being made, we establish the conditions which must dictate the laws of the interactions, so that the three points can always remain at the apexes of the equilateral triangle (Langrangian solution), or remain always on a straight line (Eulerian solution).The author believes that such general treatment of the three-body problem can be useful for theoretical studies in celestial mechanics and also for practical applications in the study of isolated stellar systems.
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17.
The empirical evidence for a connection between type and relative angular momentum of galaxies is reviewed and some constraints for the theoretical explanation are discussed.
.
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18.
The problem of stability of the equilibrium points in the problem of motion of a mass point in the neighbourhood of a rotating triaxial ellipsoid in a degenerate case (the Gaussian of the Hamiltonian is equal to zero) is investigated.It is proved that the equilibrium points in the degenerate case are stable in the strict sence.
Résumé On étudie le problème de la stabilité des positions d'équilibre relatif dans le problème du mouvement du point matériel au voisinage de l'ellipsoid à trois axes tournant dans un cas dégénéré (le gaussian du Hamiltonian égal zéro).On a démontré que des positions d'équilibre relatif dans le dégénéré sont stables dans le sens rigoureux.
( )., .
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19.
The period of very high energy (E>2×1012 eV) gamma-ray emission of Cyg X-3 by using the data of observations of the source made during 6 years, 1972–1977, was specified. The value of the period is equal to 0.199 683±1×10–6 days. Phase histogram reveals two peaks, one lagging the other by 0.6 of the period. The averaged 6 year data amounts to 1.8×10–10 quanta cm–2 s–1 (peak intensity). It corresponds to luminosity of about 1.2×1037 erg s–1 if one assumes that an emission is isotropical and the distance is equal to 10 kpc.
- E>2×1012 Cyg X-3 . 1972–1977 . - T=0,199 683 ±10–6 . , 0,6 . 1,8×10–10 –2 –1 ( ), 1,2×1037 / 10 .
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20.
. . .
Transfer of resonance radiation in infinite medium is considered as a process of random walks of photons. Close relation is shown to exist between the problems of transfer of line radiation and the stable distributions of the probability theory. This relation is used as a basis of a new method for the investigation of the asymptotic properties of the radiation field far from the sources.

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