共查询到20条相似文献，搜索用时 250 毫秒
1.
An analysis is made of the implications of assuming that suprathermal dust grains (a3×108 cm) of intergalactic origin may acquire cosmic ray energies as high as 1020 eV. These dust grains may attain suprathermal energy (v
g3×108 cm s–1) by the Fermi process. Initially the dust grains are accelerated by the radiation pressure against the drag of the ambient gas of the medium, but once these dust grains attain a terminal velocity (U105 cm s–1), then they may be expelled out of the galactic region into the intergalactic medium and finally acquire high energy 相似文献
2.
Ajoy Kumar Dasgupta 《Astrophysics and Space Science》1978,59(2):347-354
Charged dust grains of radiia3×10–6 cm could be a help in understanding the production of primary cosmic ray particles in extensive air showers (EAS). A two-stage acceleration mechanism is proposed in order to accelerate dust grains up to relativistic energy. In the first stage, dust grains acquire suprathermal energy (Suprathermal Grains) by the Fermi mechanism. In the second stage, suprathermal grains attain relativistic energy by the Alfvén magnetic pumping mechanism yielding the primary cosmic ray particles. Ionization loss has been considered to be a most important loss mechanism for charged dust grains in a fully ionized medium. It is suggested that graphite dust grains of intergalactic origin may be responsible for high energy (>1020 eV) cosmic rays. 相似文献
3.
A. K. Dasgupta 《Astrophysics and Space Science》1980,72(2):271-280
The physical conditions under which suprathermal grains can be produced when they are accelerated by radiation pressure against the drag of ambient gas are investigated. It is found that dust grains may attain a terminal velocityU (=105 cm s–1) in most regions and move out of the midplane of the source region about a distance |z|100 pc. Once clear of the main gas/dust layer the dust grains (a3×10–6 cm) may then attain suprathermal energy (V
g
3×108 cm s–1) by the Fermi process. 相似文献
4.
The observations of the reddening of the distant galaxies and the weak diffuse radiation in the clusters of galaxies can be interpreted as a consequence of the presence of dust grains in the intergalactic medium. When allowance is made for the destruction of the grains in collision with particles of the hot gas, its lifetime is about 107–108 yr at a gas concentrationn
g
10–3 cm–3. The detection of the infrared (IR) emission from the galaxy clusters might be the test for the proof of the presence of dust grains in the intergalactic medium. In this paper the estimates of the expected intensities and fluxes of IR emission for the spectral region 50–300 are presented for two galaxy clusters in Coma and Perseus. The parameters of the hot gas spatial distribution are chosen from X-ray observations. Having assumed that intergalactic dust can be ejected only from the galaxies, we used such a model for intergalactic dust grains which explains very well the interstellar dust effects. It is shown that the dust temperature, which is determined from the general energetic balance of the dust grains, can achieve some scores of degrees of Kelvin. Two models of the dust spatial distribution are considered. It is found that the maximum of IR flux for the Coma cluster lies near =100 and the same for the Perseus cluster near 50–70. The total fluxes of IR emission from these clusters are about 105–106 Jy and can be detected by modern observational methods. 相似文献
5.
6.
High resolution OVRO CO 1–0 observations of the inner 30 in the LINER galaxy NGC 5218 reveal the presence of a double centrally peaked molecular concentration with extensions out to a radius of 12. The molecular mass detected is 2.4 × 109 M and the gas surface density is high, 3000 M pc square in the inner 500 pc. The SFR is 2–3 M yr–1 and the SFE is 13, which are low or moderate values for that gas surface density. We interpret the inner feature as a rotating molecular ring with a radius of 200 pc. We furthermore suggest that the LINER activity in NGC 5218 is not caused by an aging starburst, but by a buried AGN. 相似文献
7.
Analytic and numerical results are presented for the growth rate of Langmuir waves due to a loss-cone distribution of energetic electrons. The effect of the magnetic field on the wave-particle interaction is ignored, and the resonance condition is described in terms of a resonance hyperboloid in momentum space. The collisional evolution of a distribution of magnetically trapped electrons is followed numerically to show how a gap distribution develops. The growth is most favorable for an intermediate sized loss cone ( 45 °) and a gap distribution in which the mean energy of the suprathermal electrons is much larger than the thermal energy of the background electrons. It is plausible that loss-cone gap distributions do develop in the solar corona, and that they should lead to second harmonic plasma emission weakly polarized in the x-mode. 相似文献
8.
Ajoy Kumar Dasgupta 《Astrophysics and Space Science》1979,63(2):517-523
Charged dust grains of radiia3×10–63×10–5 cm may acquire relativistic energy (>1018 eV) in the intergalactic medium. In order to attain relativistic energy, dust grains have to move in and out (scattering) of the magnetic field of the medium. A relativistic grain of radiusa10–5 cm with Lorentz factor 103 approaching the Earth will break up either due to electrostatic charge or due to sputtering about 150100 km, and may scatter solar photons via a fluorescence process. Dust grains may also melt into droplets in the solar vicinity and may contribute towards observed gamma-ray bursts. 相似文献
9.
Г. И. Ширмин 《Celestial Mechanics and Dynamical Astronomy》1975,11(4):483-515
1937 - (, 1938). , , , , . , . . (, 1938), , . - (, 1938; Szebehely, 1967)., , . . - (, 1938), . — — . , , . , . . , . , , . . (, 1944). , .
In 1937, the Celestial Mechanics and Cosmogony section of the Sternberg State Astronomical Institute undertook the task of evaluating the Gylden-Moulton hypothesis on the origin of the Gegenshein from the standpoint of celestial mechanics. That investigation, which the authors themselves considered preliminary, contains nonetheless a series of important results. For example, G. N. Duboshin showed that in the planar, circular, restricted three-body problem, periodic motion of finite amplitude in the neighborhood of a collinear libration point is unstable according to Lyapunov's criterion both in the proper and in the orbital sense. The latter result is incompatible with the above named hypothesis, and thus appears as one of the serious objections among the many known negative conclusions relative to the existence of the Gylden-Moulton cluster.Unfortunately, most of the specific problems which arose in the above named research have not been considered since. One of these, the problem of the stability of three-dimensional periodic orbits in the neighborhood of a collinear libration point is solved in the present paper, within the limits of the three-dimensional, circular, restricted, three-body problem. Major attention is given to the investigation of stability in the orbital sense, since in the proper sense all orbits are unstable according to Lyapunov theory. It is shown that in order to resolve the question of stability, it is sufficient to consider the equations in their variational form. Analysis of the roots of the corresponding characteristic equations determines the orbital stability of planar and three-dimensional solutions, which later can be confirmed by calculation of the characteristic exponents appearing in the periodic solutions of the N. A. Artemiev method. Finally, the possibility of conditional stability in the linear approximation is proved.相似文献
10.
A. K. Dasgupta 《Astrophysics and Space Science》1981,76(1):119-128
The physical conditions under which suprathermal grains may loose energy and the processes involving the grains (a3×10–6 cm) destruction are investigated. It is found that the dust grain once attaining the velocityU (105 cm s–1) may attain suprathermal energy (v
g3×108 cm s–1) and subsequently may also attain relativistic energy are almost indestructible in the accelerating phase. 相似文献
11.
M. Fracassini F. Manzolini L. E. Pasinetti M. Ruggenini 《Astrophysics and Space Science》1980,69(2):401-423
Apparent radius, visual brightness, effective temperature and absolute radius for 416 B5 v-F5 v stars of the catalogue of the Geneva Observatory (Rufener, 1976) have been determined.Twenty-eight stars, anomalous in log versus (m
v)0 diagrams, have been singled out. A good correlation for seven stars, in common with the list of Hanbury Brownet al. (1974), has been found. Similar parameters determined for 279 B5 v-F5 v stars of two preceding papers (Fracassiniet al., 1973, 1975) have allowed us to determine the averaged diagrams logq
v/q, logR/R
and logT
e versus (B-V)0 for 695 B5 v-F5 v stars.Moreover, in the present paper a good correlation logq
v/q versus logR/R
and careful relation M
v=–7.40logR/R
+3.31 for B5 v-F5 v stars have been determined. Plain correlations between logR/R
and blanketing parameterm
2 for some spectral types seem to point out that there arereal differences in the absolute radii of stars of thesame spectral type, in agreement with recent researches on the HR diagram (Houck and Fesen, 1978).Systematic differences between double (spectroscopic and visual) and single stars are found. In particular, the averaged relation m
2 versus logR/R
shows that A2 v-F5 v double stars may have a higher metallicity indexm
2 and smaller absolute radii than single stars. Finally, the diagram logv sini versus logR/R
confirms some properties of binary systems found by other researchers (Huang, 1966; Plavec, 1970; Levato, 1974; Kitamura and Kondo, 1978).Thesis for the degree in Applied Physics. 相似文献
12.
( , 1977; , 1977). , , , . . 相似文献
13.
Chiyoe Koike Hiroichi Hasegawa Noriaki Asada Takeshi Hattori 《Astrophysics and Space Science》1981,79(1):77-85
Extinction measurements were made for some silicate and iron-oxide mineral grains in mid- and far-infrared region. For far-infrared region, high temperature magnesium silicates such as olivine and pyroxenes show the absorption spectra of steep dependence as –3 ( being the wavelength) with some peak structure, but the spectrum of magnetite shows –1 dependence. 相似文献
14.
Gordon E. Bromage 《Astrophysics and Space Science》1972,15(3):426-461
The possibility that the diffuse interstellar lines and bands are but structure in the continuous extinction by dust grains is considered in detail. The lines are assumed to arise from impurities in the grains. Profiles of the strongest diffuse features are computed for a wide variety of host grain types and sizes, including size distributions of particles, and spheroidal and coated spherical grains.New observational profiles, of which 4430, 4765 and 4885 have been derived from automated spectrophotometry of electronographic spectra, are also presented; and comparison is made between theory and observation. The most useful tool of comparison is found to be the ratio of maximum apparent emission in the violet wing to maximum apparent absorption, . This ratio increases with size of the host particle, and with both real and imaginary parts of its refractive index; but is independent of the observed variations in strength and width of a particular line. The ratio is larger for 4430 than for the other lines.Taking into account current opinion as to the composition of interstellar dust, the observations may be explained by the presence of impurities in either silicate grains with effective radii of about 120 nm, or possibly graphite grains about 50 nm in radius coated with a thin dielectric condensate. None of the observed profiles are at variance with the hypothesis that all the lines arise from the same impurities in the same type of grains. The concentration of such impurities needed to reproduce the observed line profiles and strengths is only about one in 104 atoms in the grain. 相似文献
15.
Masaya Saitou 《Astrophysics and Space Science》1989,162(1):47-56
Some peculiarities in the behaviour of a model self-gravitating system described by hydrodynamical equations and isothermal equation of state connected with the presence of thermodynamical fluctuations in real systems were investigated in numerical experiment. The values of density and velocity , , respectively, were computed by numerical code perturbed on each time-step and in each computational cell by random values , for modeling such fluctuations. Perturbed values
i
=
i
+
i
,v
i
=
i
+ v
i
were used to initiate the next step of computations. This procedure is equivalent to an introduction into original hydrodynamical equations of Langevin sources which are random functions. It is shown that these small fluctuations (= v =0,2 =v
2 = 10–8) grow many times in marginally-stable state. 相似文献
16.
We present near infrared maps of the planetary nebula IC 418 taken at 5 arc sec spatial resolution. These show an extremely compact source structure at 1.65 m, and very much broader and more elliptical emission distributions at 2.2 and 3.6 m. The possibility that the near infrared continuum derives from small grains with low thermal capacity is discussed, and synthetic spectra are derived. These indicate a very much slower variation of flux with wavelength than would be deduced for grains at unitary temperature, and imply a near infrared continuum which is significantly cooler than maximum grain temperatures. Fits to the spectrum of IC 418 suggest that peak grain temperatures may approachT
p0103 K (for –2), for instance, compared to the observed colour temperature of 650 K.Finally, the relevant grains are required to be refractory and, given the large C/O ratio in this nebula, probably consist of graphite. Their mass is also required to be small, and is probably of order 2×10–7
M
. This compares with the probable total mass for large dust grains of 10–4
M
. Although they are both small and warm, such grains would be expected to persist over the lifetime of the nebula, and may also be responsible for various NIR band emission features. 相似文献
17.
, , , , . . . , . , . . ( , 1970) . , . 相似文献
18.
The aim of the present paper is to prove that the system of partial differential equations, which define a set of curvilinear coordinates , , that are orthogonal to the Roche equipotentials (r, , ) incorporating the effects of both rotationaland tidal distortion, does not admit of any formal integrals; and can be solved only numerically in an asymptotic manner. This fact is related with analytic properties of the problem of three bodies, in which represents the potential. 相似文献
19.
The tenth list of objects from the BIG (Byurakan-IRAS Galaxies) sample, containing 104 galaxies identified with 60 point sources from the IRAS PSC catalog, is introduced. The identifications have been made in the region +69°+73° and 09h50m15h20m with an area of 107 sq.deg. The identified objects include 13 Sy candidates, 5 compact star-formation galaxies, 11 interacting pairs (including 5 merger candidates) and 1 interacting triple system, 5 LSB galaxies, and 5 groups. 21 objects are also identified with radio sources. The optical coordinates, their deviations from the IR coordinates, V stellar magnitudes, morphological types, angular sizes of the central regions, and position angles have been determined. The identified galaxies are of Sa-Sc, SB, and Irr morphological types, the optical stellar magnitudes lie in the range 15m.0-21m.5, and the angular sizes of the central regions lie in the range 3-32. Finding charts from the DSS2 are included for these objects. 相似文献
20.
A. Hruška 《Astrophysics and Space Science》1977,50(1):153-161
One component of a three-fluid adiabatic plasma is under certain conditions contained in a restricted region of space by a large-scale electrostatic field generated within the plasma. The containment is discussed here for plasma consisting of ions and two populations of electrons characterized by different pitch angle distribution functions.The bouncing motion of electrons along open fieldlines between a magnetic mirror and an electrostatic mirror produces a velocity distribution function similar to that generated by bouncing particles on closed fieldlines. 相似文献