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1.
Hong Wei Li 《Solar physics》1986,104(1):131-136
The variations of the growth rates of ECM at first four harmonics in X-, Z-, and O-modes excited by a hollow beam distribution of weakly relativistic electrons with a parameter
p
/
e
are presented in this paper. The results show that the second harmonic of ECM in X-mode dominates the instability if < 1, and if 1.2 , 2 or 2.2 3 the third or fourth harmonic will dominate. The second and third harmonics of Z-mode waves grow faster only if 2 2.2 and 3 3.2, respectively, so it would not be a competition in most cases. It is suggested that the ECM emission at these harmonics in X-mode is a possible mechanism to produce solar spike emissions with high brightness temperature at shorter and longer decimetric wavelengths.Proceedings of the Workshop on Radio Continua during Solar Flares, held at Duino (Trieste), Italy, 27–31 May, 1985.On leave from the Department of Astronomy, Nanjing University, Nanjing, The People's Republic of China. 相似文献
2.
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
3.
Analytic structure of high-density steady isothermal spheres is discussed using the TOV equation of hydrostatic equilibrium which satisfies an equation of state of the kind:P = K
g
, =
g
c
2.Approximate analytical solutions to the Tolman-Oppenheimer-Volkoff (TOV) equations of hydrostatic equilibrium in (, ), (,U) and (u, v) phase planes in concise and simple form useful for short computer programmes or on small calculator, have been given. In Figures 1, 2, and 3, respectively, we display the qualitative behaviours of the ratio of gas density
g
to the central density
gc
,
g
/
gc
; pressureP to the
gc
,P/
gc
; and the metric componente
–, for three representative general relativistic (GR) isothermal configurations =0.1, 0.2, and 0.3. Figure 4 shows the solution curve (, ) for =0.1, 0.2, and 0.3 (=0 represents the classical (Newtonian) curve). Numerical values of physical quantitiesv (=4r
2
P
*(r)), in steps ofu (=M(r)/r)=0.03, and the mass functionU, in steps of =0.2 (dimensionless radial distance), are given, respectively, in Tables I and II. Other interesting features of the configurations, such as ratio of gravitational radius 2GM/c
2 to the coordinate radiusR, mass distributionM(r)/M, pressure (or density) distributionP/P
c
, binding energy (B.E.), etc., have also been incorporated in the text. It has further been shown that velocity of sound inside the configurations is always less than the velocity of light.Part of the work done at Azerbaijan State University, Baku, U.S.S.R., and Mosul University, Mosul, Iraq, 1985-1986 相似文献
4.
V. V. Markellos 《Astrophysics and Space Science》1975,36(2):245-272
This paper reports on the numerical determination of families of periodic oscillations in the case =0.000 95 of the restricted problem. The families emanating out of the collinear Lagrangian pointsL
1,L
2,L
3 are examined as well as some asymmetric periodic oscillations related to them. An effort is made to complete the global picture of simple-periodic symmetric oscillations in the present case of the problem (the S-J case). This is done by examining the orbits with initial conditions such that the infinitesimal body starts from a position on the 1-axis (02 = 0) with a negative initial velocity
perpendicular to this axis
. In a previous article this investigation has been carried out for negative values of 01, where the position of the small primary defines 1=0. Now we proceed to consider orbits with 01>0. The phase portrait of asymmetric periodic orbits is also examined. 相似文献
5.
Robert F. Howard 《Solar physics》1991,135(2):327-337
Digitized Mount Wilson sunspot data from 1917 to 1985 are analyzed to examine meridional motion and rotation properties as a function of latitude and distance () from the average latitude of activity (0) in each hemisphere. Latitude dependence similar to previous results is found, but only for spot groups whose areas are decreasing from one day to the next. A previous study of active region magnetic fields, using this technique of motions as a function of the average latitude of activity, had shown meridional motions on average toward 0. In this analysis of spot data some evidence is seen for motion away from 0, with some slight evidence for faster rotation equatorward of 0 and slower motion poleward of 0, similar to the torsional oscillation phenomenon. For reasons that are not clear, both of these effects are significantly more pronounced for sunspot groups whose areas are decreasing.Operated by the Association of Universities for Research in Astronomy, Inc., under Cooperative Agreement with the National Science Foundation. 相似文献
6.
The present paper extends the analysis by Sakurai, Goossens, and Hollweg (1991) on resonant Alfvén waves in nonuniform magnetic flux tubes. It proves that the fundamental conservation law for resonant Alfvén waves found in ideal MHD by Sakurai, Goossens, and Hollweg remains valid in dissipative MHD. This guarantees that the jump conditions of Sakurai, Goossens, and Hollweg, that connect the ideal MHD solutions for
r
, andP across the dissipative layer, are correct. In addition, the present paper replaces the complicated dissipative MHD solutions obtained by Sakurai, Goossens, and Hollweg for
r
, andP in terms of double integrals of Hankel functions of complex argument of order
with compact analytical solutions that allow a straightforward mathematical and physical interpretation. Finally, it presents an analytical dissipative MHD solution for the component of the Lagrangian displacement in the magnetic surfaces perpendicular to the magnetic field lines which enables us to determine the dominant dynamics of resonant Alfvén waves in dissipative MHD. 相似文献
7.
R. Grant Athay 《Solar physics》1988,116(2):223-237
An attempt is made in this paper to determine the coefficient a in a power-law relationship of the form V
~T
between the r.m.s. velocity fluctuation, V
for raster images with 3 resolution and the temperature, T of line formation using SMM solar data. For T between 8000 and 105 K, the data suggest a best fit with 3/4 < 1. It is argued, however, that unresolved fine structure tends to reduce the observed value of V
and that higher resolution data may yield different values for . Skylab data have shown that the non-thermal line broadening velocity, , is proportional to T
1/2. Also, for all temperatures less than 105 K, V
. This latter result, however, is again dependent on spatial resolution and may not be true in observations made with sufficient spatial resolution. The magnitudes of both V
and indicate that bulk motions play important roles in the structure of the solar atmosphere as well as in its energy and momentum balance. It is important, therefore, to identify the true nature of such motions with better accuracy than is possible with currently available data.The National Center for Atmospheric Research is sponsored by the National Science Foundation. 相似文献
8.
The exact geometry of the Roche curvilinear coordinates (, , ) in which corresponds to the zero-velocity surfaces is investigated numerically in the plane, as well as in the spatial, case for various values of the mass-ratio between the two point-masses (m
1,m
2) constituting a binary system.The geometry of zero-velocity surfaces specified by -values at the Lagrangian points are first discussed by taking their intersections with various planes parallel to thexy-, xz- andyz-planes. The intersection of the zero-velocity surface specified by the -value at the Lagrangian equilateral-triangle pointsL
4,5 with the planex=1/2 discloses two invariable curves passing through the pointsL
4,5 and situated symmetrically with respect to thexy-plane whose form is independent of the mass-ratio.The geometry of the remaining two coordinates (, ) orthogonal to the zero-velocity surfaces is investigated in thexy- andxz-planes from extensive numerical integrations of differential equations generated from the orthogonality relations among the coordinates. The curves (x, y)=constant in thexy-plane are found to be separated into three families by definite envelopes acting as boundaries whose forms depend upon the mass-ratio only: the inner -constant curves associated with the masspointm
1, the inner -constant curves associated with the mass-pointm
2 and the outer -constant curves. All the -constant curves in thexy-plane coalesce at either of the Lagrangian equilateraltriangle pointsL
4,5, except for a limiting case coincident with thex-axis. The curves (x, z)=constant in thexz-plane are also separated by definite envelopes depending upon the mass-ratio into different families: the inner -constant curves associated with the mass-pointm
1, the inner -constant curves associated with the mass-pointm
2 and the outer -constant curves on both sides out of the envelopes. For larger values ofz, the curves =constant tend asymptotically to the line perpendicular to thex-axis and passing through the centre of mass of the system, except for a limiting case coincident with thex-axis. The geometrical aspects of the envelopes for the curves (x, y)=constant in thexy-plane and the curves (x, z)=constant in thexz-plane are also discussed independently.In the three-dimensional space, the Roche coordinates can be conveniently defined in such a way as to correspond to the polar coordinates in the immediate neighbourhood of the origin, and to the cylindrical coordinates at great distances. From numerical integrations of simultaneous differential equations generating spatial curves orthogonal to the zero-velocity surfaces, the surfaces (x, y, z)=constant and the surfaces (x, y, z)=constant are constructed as groups of such spatial curves with common values of some parameters specifying the respective surfaces.On leave of absence from the University of Tokyo as an Honorary Fellow of the Victoria University of Manchester. 相似文献
9.
A spectroscopic investigation of a quiescent prominence has been performed: the line profiles of the H and K lines have been carefully determined in all regions of the prominence where these emissions are likely to originate in optically thin layers. Therefore we have been able to study the electron temperature T
e and the microturbulent velocity in the outer parts of the prominence. We find that on the average, T
e = 5700 K (Figure 1) and = 6.7 km s-1 (Figure 2) which are in very good agreement with classical data. Figure 3 represents the radial velocity measurements and Figure 4 the ratio of the total intensity of H to K lines. Thus the prominence we have observed does not show for T
e and the regular increase outward which has been described by Hirayama (1971). On the other hand increases towards the Equator, in the dynamically active part of the prominence, which could indicate that represents the effect of macroturbulence rather than microturbulence (Kawaguchi, 1966). In this part of the prominence only the K line is in emission and the average value of the microturbulence is 9.4 km s-1, the radial velocity is also generally increasing. At last, according to the absolute intensities of the H and K lines, the electron density in the outer layers of the prominence is no more than 1 × 1010 cm-3. 相似文献
10.
Résumé On étudie les spectres des spicules observés simultanément dans les raies K et D3 en fonction du temps et de l'altitude (2000<h<5000 km). Les mesures de la variation de l'intensité centrale I
0 avec l'altitude, sont données dans le Tableau I. On donne des résultats comparatifs concernant l'énergie émise E
k et E
D3.La Figure 1 représente les variations de la largeur à mi-intensité des profils d'émission, (L) en fonction du temps et la Figure 2 en fonction de la hauteur.La classification des spicules en deux groupes: profil large (LW) et profil étroit (LN) a été confirmée. Il y a 2 fois plus de spicules LW que LN, la durée de vie des LN étant <2,5 min. Le Tableau II donne les valeurs moyennes de la largeur réduite L/.A l'aide des valeurs L, on détermine la microturbulence () dans les spicules en fonction de la hauteur (Figure 3, pour la raie K). La turbulence de la raie D3 est donnée dans un tableau dans le texte. Les résultats sont en bon accord. L'interprétation de ces résultats suggère que la microturbulence a deux composantes
0 et
e. Pour les LN on a
0 seul pour les LW on a
0 +
0, où
0 est la turbulence au centre des spicules à l'endroit du champ magnétique fort (Figure 4a) et
0 est la turbulence vers l'extérieur des spicules LW, là où le champ est faible (Figure 4b).
We study in this paper the spectra of spicules on the solar limb observed simultaneously in the K and D3 lines in terms of time and altitude (2000<h<5000 km). The measures of the variation of the central intensity I 0 with the altitude are given in Table I. We are also giving comparative results concerning the energy emitted EK and ED3 (Section 4).For different spicules, Figure 1 represents the variations of the total width at half intensity (L) of the emission profiles in terms of time and Figure 2 in terms of height.The classification of spicules in two groups: wide profile (LW) and narrow profile (LN) has been confirmed. There are approximately twice as many LW spicules as LN, the lifetime of LN spicules seems to be <2.5 min. Table II gives the average values of L/.With the help of L values, we can determine the microturbulence () in the spicules in function of the height (Figure 3, for the K line). The turbulence of the D3 line is given in a table in the text (Section 5.3). The results of both lines are concordant and the interpretation which we suggest (Section 5.4) is that the microturbulence has, generally speaking, two components 0 and 0. For the LN we have 0 alone, and for the LW we have 0 + e, 0 being the turbulence at the center of spicules where the magnetic field is strong (Figure 4a), whereas the e is the turbulence towards the exterior of the LW spicules, where the magnetic field is weak (Figure 4b).相似文献
11.
A model of a first generation intermediate star of 5M
, with Z=0 has been considered. The model is at an advanced stage of its evolution and has a double shell burning. It burns helium in the inner shell, and hydrogen, via CNO cycle, in the outer shell.
=(log/log)
T
and
T
=(log/logT)
were computed allowing for the oscillations of the relative mass abundance of the reagents in nuclear reactions. Including
=(log/log)
T
and
=(log/logT)
of mean molecular weight and the effect of the oscillations of abundances due to nuclear reactions, stability was studied. Contrary to the results of the static calculations, we found that instability due to the excitation mechanism provided by the high temperature sensitivity of energy generation rate propagates up to the surface. Thus the model in question was found to be unstable against radial adiabatic pulsations, in its fundamental mode. 相似文献
12.
P. M. Papaelias 《Earth, Moon, and Planets》1994,65(1):71-77
The lifetime of antimatter fragments which may enter the Earth's atmosphere in the form of meteors is determined in this paper, for cases in which the annihilation may be accompanied by the evaporation process. The antimatter object can be penetrated by the nucleon - antinucleon annihilation products, which can be generated by interactions of atoms of antimatter fragments with the atmospheric molecules. Vaporization of its own antiatoms may be followed, in case of a high rate of annihilation, so that the lifetime of the antimatter object may become shorter, compared with the case of annihilation without vapor production of the meteor. The lifetime of the antimatter fragment is dependent upon the temperature of the object and thus vaporization of such an object would last for as long as =R/, where is the intensity of evaporation, its density andR its radius. 相似文献
13.
Following up our previous analysis of cyclotron radiation in anisotropic plasmas, we derived expression for the power received at a far field point per unit frequency range along the group velocity direction dP(, )/d. We then carry out a series of numerical analysis presenting the spectral features rather than directional features of cyclotron radiation. In particular, we analyse the power received per unit solid angle per unit frequency range d2
P(, )/(d d). It is expected the analysis result presented here can be compared directly with observation for parameters pertaining to astrophysical plasmas in stellar and terrestrial atmospheres. 相似文献
14.
Various methods are explored for obtaining regularized solutions of the severely ill-posed Laplace inversion problem involved in deriving plasma temperature (T) structure (differential emission measure(T)) from bremsstrahlung spectra. Inversions of simulated data show that zero-order regularisation (Tikhonov regularisation inL
2 space) is very unsatisfactory even with weighting, while first-order regularisation (Tikhonov regularisation in Sobolev space) yields reasonable results.The method is applied to a high-resolution hard X-ray flare spectrum observed by Lin and Schwartz (1987) and yields a positive solution for(T) showing that a purely thermal interpretation is possible for that event. The form of(T) found has two broad features: one peaking at around 107 K and falling off steeply toward 2 × 108 K; a second spread around a peak near 4.5 × 108 K. The interpretation of such(T) in terms of plasma heating and conductive flux is discussed in terms of plasma heat fluxes and heating rates. For 1-D geometry, the distribution of the plasma heating rateH(T) per unit volume is inferred from(T) in the limits of classical diffusive conduction and of saturated heat flux, the former being relevant atT below around 5 × 107 K and the latter at much higherT. We find there exists a maximum inH(T) around 2 × 108 K, a fact which may be important for energy release theories. 相似文献
15.
Paul S. Wesson 《Astrophysics and Space Science》1978,54(2):489-495
An exact solution of Einstein's equation is stated in which the density (), pressure (p), scale factorS and metric coefficients are functions of only one dimensionless self-similar variable,ct/R, wheret is cosmic time andR is a co-moving radial coordinate. The solution represents a cosmology that begins as a static sphere having R
–2 and evolves into an expanding model which is pressure-free and has a hierarchical type of density law ( R
–, approximately, with =a number, 02). It is suggested that this model should supersede the previous models of Wesson and other workers, since it appears to be the simplest cosmology for a hierarchy. 相似文献
16.
Koujun Yamashita 《Astrophysics and Space Science》1968,2(1):4-22
Rocket-borne photon counters sensitive to bands 1060–1180, 1230–1350, and 1350–1480 were used to measure the celestial ultraviolet radiation above the terrestrial atmosphere. The energy spectra of six objects, Leo, CMa, Ori, , , Ori (combined), Ori, and Tau were obtained. The comparison of them with those calculated with the stellar model atmospheres indicates the deficiency of about 1 mag. in the ultraviolet region, when corrected for interstellar extinction, for all stars except Tau. The observed spectrum of Tau agreed with the theoretical one for normal interstellar extinction. The effects of line blanketing were examined for B1 and B2 stars, and found to account for a part of the difference between the observed and the theoretical values. 相似文献
17.
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
18.
Ioan Todoran 《Astrophysics and Space Science》1992,187(1):119-126
By use of the mass-point model, the equations of the equipotential surfaces are reviewed. A difference between the time-dependent potential function and zero relative velocity surfaces is put in evidence. A drawback in the time-dependent transformation between (, , ) and (x, y, z) coordinate systems is underlined. 相似文献
19.
I. E. Val'tts 《Astrophysics》1989,30(1):14-18
Conclusions Thus, we have considered the possibility of comparing unidentified lines of quasar spectra with unidentified lines of stellar spectra. Since the majority of absorption lines in the spectrum of Oph have wavelength shorter than 1000 Å, a comparison could be made in practice only with the absorption lines of Pup. Significant excesses in the number of coincidences over the mean level were not found, but in the case of the quasar 2351–154 the number of such coincidences within the reliable system is somewhat higher than for the other spectra. It is interesting that all the lines in the spectrum of this quasar that we distinguished belong to the unidentified lines.Of course, such comparison of the absorption lines of quasar spectra and the lines of stellar spectra can be regarded only as a weak attempt to win back in the L forest at least some lines for the absorption systems. However, for more distant absorption systems that could possibly be detected this method could play a more important part.Institute of Cosmic Research, USSR Academy of Sciences. Translated from Astrofizika, Vol. 38, No. 1, pp. 27–33, January–February, 1989. 相似文献
20.
From 15:33 through 16:02 UT on 13 June 1998, observations of an erupting filament as it crossed solar disk center were obtained with the NSO/KPVT and SOHO/CDS instruments as part of the SOHO Joint Observing Program 70. Context observations show that this event was the eruption of the north-east section of a small active region filament associated with NOAA 8237, that the photospheric magnetic field was changing in this active region between 12–14 June 1998, and that a coronal Moreton-wave disk event occurred, as well as a white-light CME off the south-west solar limb. The NSO/KPVT imaging spectroscopy data covered 512 × 512 arc sec of the disk center and were spectrally centered at the Hei 1083 nm line and captured ±1.0 nm of surrounding solar spectrum. The Hei absorption line is seen blue-shifted to velocities of between 200 and 300 km s–1. The true solar trajectory of the eruption is obtained by using the projected solar coordinates and by integrating the Doppler velocity. The filament travels with a total velocity of about 300 km s–1 along a path inclined roughly 49 deg to the solar surface and rises to a height of just over 1.5 solar radii before it becomes too diffuse to follow. The filament also shows internal motions with multiple Doppler components shifted by ±25 km s–1. Finally, the KPVT data show no Stokes V profiles in the Doppler-shifted Hei 1083.03 nm absorption to a limit of roughly 3×10–3 times the continuum intensity. The SOHO/CDS scanned the center of the KPVT FOV using seven EUV lines; Doppler-shifted filament emission is seen in lines from Hei 58.4 nm, Heii 30.4 nm, Oiv 55.5 nm, Ov 63.0 nm, Nevi 56.3 nm, and Mgx 61.0 nm representing temperatures from about 2×104K through 1×106K. Bound-free continuum absorption from Hi, without confusion from foreground emission and line emission, is seen as the filament obscures underlying chromospheric emission. A fit to the wavelength dependence of the absorption from five lines between 55.5 to 63.0 nm yields a column density H I =4.8±2.5×1017 cm–2. Spatial maps show that this filament absorption is more confined than the regions which show emission. 相似文献