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1.
Previous analyses of the orbits of spherical balloon satellites have attempted to satisfy residuals in observed perturbations in Keplerian elements, assumed to be caused by diffuse radiation pressure, by introducing small variations ins, the parameter representing the reflection characteristics of the satellite's surface. It is difficult to distinguish, however, between those perturbations caused by diffuse radiation and those caused by reflected radiation, as a result of the deformation of the assumed sphere. Following the derivation by Lucas of exact expressions for both incident and reflected radiation forces on a prolate spheroidal satellite, and the subsequent work of Aksnes pertaining to spherical satellites, the theory is extended to include the effects of diffuse radiation whilst at the same time qualifying the assumption that the radiation force acting along the Sun-satellite line can be taken as parallel to the Sun-Earth line. 相似文献
2.
3.
Transfer of resonance radiation in an 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. 相似文献
4.
Etienne Van Hemelrijck 《Earth, Moon, and Planets》1988,40(2):149-164
The latitudinal and seasonal variation of the direct solar radiation incident at the top of the atmosphere of Uranus and Neptune has been recalculated by use of updated values for the period of axial rotation and the oblateness. Values for the solar radiation are given in Watt per square meter instead of the unit used in earlier papers (calories per square centimeter per planetary day). The solar radiation averaged over a season and a year as a function of planetocentric latitude has also been reviewed. In addition, attention is made to the ratio of the solar radiation incident on an oblate planet to that incident on a spherical planet. 相似文献
5.
Akio K. Inoue Akinori Oka Taishi Nakamoto 《Monthly notices of the Royal Astronomical Society》2009,393(4):1377-1390
The temperature in the optically thick interior of protoplanetary discs is essential for the interpretation of millimetre observations of the discs, for the vertical structure of the discs, for models of the disc evolution and the planet formation, and for the chemistry in the discs. Since large icy grains have a large albedo even in the infrared, the effect of scattering of the diffuse radiation in the discs on the interior temperature should be examined. We have performed a series of numerical radiation transfer simulations, including isotropic scattering by grains with various typical sizes for the diffuse radiation as well as for the incident stellar radiation. We also have developed an analytic model including isotropic scattering to understand the physics concealed in the numerical results. With the analytic model, we have shown that the standard two-layer approach is valid only for grey opacity (i.e. grain size ≳10 μm) even without scattering. A three-layer interpretation is required for grain size ≲10 μm. When the grain size is 0.1–10 μm, the numerical simulations show that the isotropic scattering reduces the temperature of the disc interior. This reduction is nicely explained by the analytic three-layer model as a result of the energy loss by scatterings of the incident stellar radiation and of the warm diffuse radiation in the disc atmosphere. For grain size ≳10 μm (i.e. grey scattering), the numerical simulations show that the isotropic scattering does not affect the interior temperature. This is nicely explained by the analytic two-layer model; the energy loss by scattering in the disc atmosphere is exactly offset by the 'green-house effect' due to the scattering of the cold diffuse radiation in the interior. 相似文献
6.
When coronal mass ejections (CMEs) interact with the solar corona and the interplanetary medium, emissions at different wavelengths occur. On the basis of study of the various radiation mechanisms of space plasma in the case of absence of CMEs, the radio radiation mechanisms of the plasma close to the Lagrange point L1 and affected by large CMEs from February to August 1999 are statistically analyzed. As shown by the results, the main radiation mechanisms are the Bremsstrahlung, a small amount of cyclotron radiation and a still weaker recombination radiation. Also, solar microwave bursts which are associated with CMEs in the same period are investigated. The results show that the microwave bursts are of the gradual type as well as spike bursts, and that the chief radiation mechanisms are the Bremsstrahlung, cyclotron resonance radiation, plasma radiation and electronic cyclotron maser radiation. 相似文献
7.
Juri Poutanen 《Monthly notices of the Royal Astronomical Society》2002,332(2):257-270
Observations suggest that accretion discs in many X-ray binaries are likely flared. An outer edge of the disc intercepts radiation from the central X-ray source. Part of that radiation is absorbed and re-emitted in the optical/UV spectral ranges. However, a large fraction of that radiation is reflected and appears in the broad-band X-ray spectrum as a Compton reflection bump. This radiation is delayed and variability is somewhat smeared compared with the intrinsic X-ray radiation. We compute response functions for flat and flared accretion discs and for isotropic and anisotropic X-ray sources. A simple approximation for the response function which is valid in the broad range of the disc shapes and inclinations, inner and outer radii, and the plasma bulk velocity is proposed. We also study the impact of the X-ray reprocessing on temporal characteristics of X-ray binaries such as the power spectral density, auto- and cross-correlation functions, and time/phase lags. We propose a reprocessing model which explains the secondary peaks in the phase lag Fourier spectra observed in Cyg X-1 and other Galactic black hole sources. The position of the peaks could be used to determine the size of the accretion disc. 相似文献
8.
We discuss the prompt emission of gamma-ray bursts (GRBs), allowing for γγ pair production and synchrotron self-absorption.
The observed hard spectra suggest heavy pair-loading in GRBs. The re-emission of the generated pairs results in the energy
transmission from high-energy gamma-rays to long-wavelength radiation. Due to strong self-absorption, the synchrotron radiation
by pairs is in optically thick regime. Thus, the re-emission would appear as a thermal-like spectral bump in the extreme-ultraviolet/soft
X-ray band, other than the peak from the main burst. The confirmation of the thermal-like feature and the double-peak structure
by future satellites, such as Swift, would indicate that the dominant radiation mechanism in GRBs is synchrotron rather than inverse-Compton radiation. 相似文献
9.
The linear stability of the triangular equilibrium points in the photogravitational elliptic restricted three-body problem is examined and the stability regions are determined in the space of the parameters of mass, eccentricity, and radiation pressure, in the case of equal radiation factors of the two primaries. The full range of values of the common radiation factor is explored, from the gravitational caseq
1 =q
2 =q = 1 down to the critical value ofq = 1/8 at which the triangular equilibria disappear by coalescing on the rotating axis of the primaries. It is found that radiation pressure exerts a significant influence on the stability regions. For certain intervals of radiation values these regions become qualitatively different from the gravitational case as well as the solar system case considered in Paper I. There exist values of the common radiation factor, in the range considered, for which the triangular equilibrium points are stable for the entire range of mass distribution among the primaries and for large eccentricities of their orbits. 相似文献
10.
O. Bschorr 《Solar physics》1982,79(2):327-331
In addition to the heating the corona by sound waves, there exists a radiation pressure caused by the absorption of acoustic waves as well as plasma waves. Whereas in the hydrostatic balance of the solar atmosphere, the light pressure can be neglected, the radiation pressure due to acoustic waves and Alfvén waves is much higher and has to be taken into account.In the solar atmosphere, the acoustic radiation pressure is generated by (i) absorption of sound energy, (ii) reflection of sound energy, and (iii) change of the sound velocity.The radiation pressure caused by absorption is dominating within the solar corona. The radiation pressure caused by reflection and the wave velocity change probably produce a pressure inversion in the transition zone between chromosphere and corona. Furthermore, the spicule phenomena are due to instationary radiation pressure. 相似文献
11.
We have numerically investigated the stability of retrograde orbits/trajectories around Jupiter and the smaller of the primaries in binary systems RW-Monocerotis (RW-Mon) and Krüger-60 in the presence of radiation. A trajectory is considered as stable if it remains around the smaller mass for at least few hundred binary periods. In case of circular binary orbit, we find that the third order resonance provides the basis for reduction of stability region of retrograde motion of particle in RW-Mon and Sun-Jupiter system both in the presence and absence of radiation. Considering finite ellipticity in Sun-Jupiter system we find that for distant retrograde orbits, radiation from the Sun increases the width of the stable region and covers a significant portion of the region obtained in the absence of solar radiation. Further, due to solar radiation pressure, the stable region in the neighborhood of Jupiter has been found to shift much below the characteristic asymptotic line for the periodic retrograde orbits. In case of Krüger-60 we observe the distant retrograde orbits around the smaller of the primaries get affected considerably with increase in radiation parameter β1. Further the range of velocities for which stable motion may persist narrows down for distant retrograde orbits in this system. 相似文献
12.
We have deduced the intensity spectral function for the spin-flip synchrotron radiation in the presence of a plasma. Using parameters appropriate to astrophysical conditions, we have attempted to compare the characteristics of the spin-flip synchrotron radiation and the normal synchrotron radiation in a magnetized plasma arising from an electron or positron rotating around the magnetic field. A rotating charge gives the maximum possible synchrotron radiative power as compared to a charge of the same energy but moving in a helical path. Since the spin-flip radiational does not depend on the form of the orbital path, whether circular or helical or along a straight line, the analysis presented here gives the lower limit of the relative importance of the spin-flip radiation to the normal synchrotron radiation emitted by the same radiator. 相似文献
13.
Yang Jiang-he Fan Jun-hui Zhang Yue-lian Yang Ru-shu Tuo Man-xian Nie Jian-jun 《Chinese Astronomy and Astrophysics》2019,43(1):23-33
The X-ray emissions of blazars are located at the end of synchrotron radiation and the beginning of inverse Compton radiation. Therefore, the origin of the X-ray emissions is rather complex. The spectral energy distributions (SEDs) of blazars from radio to X-ray bands can be fitted approximatively by a parabolic function. If we consider approximately the fitting curves as the physical spectra of blazars to analyze the X-ray emissions of Fermi blazars, the results show that: (1) The X-ray emissions of blazars contain two components, i.e. the synchrotron radiation and inverse Compton radiation, which can be simply separated by these fitting curves; (2) the higher the synchrotron peak frequency of the source, the greater the synchrotron radiation component, and the less the inverse Compton radiation component; (3) at 1 keV of the X-ray waveband, the synchrotron radiation component accounts for 17%, 27%, and 73% of the total X-ray emission, for FSRQs (Flat Spectrum Radio Quasars), LBLs (Low synchrotron peak frequency BL Lac objects), and HBLs (High synchrotron peak frequency BL Lac objects), respectively; (4) there is a strong positive correlation between the synchrotron peak frequency and the synchrotron radiation flux density at 1 keV, while no correlation exists between the synchrotron peak frequency and the inverse Compton radiation flux density; (5) the radiation mechanism of LBLs may be similar to that of FSRQs in the X-ray waveband. 相似文献
14.
G. A. Shah 《Astrophysics and Space Science》1991,178(2):251-260
The asymmetry parameter of the scattering diagram and the efficiency for radiation pressure for scattering by a very large dielectric sphere conforming to geometrical optics and diffraction, have been investigated beyond the limit of existing literature. A new feature of shallow broad extremum (resonance) has been found in the asymmetry parameter as well as in the radiation pressure both as function of the index of refraction. 相似文献
15.
The linear stability of the inner collinear equilibrium point of the photogravitational elliptic restricted three-body problem is examined and the stability regions are determined in the space of the parameters of mass, eccentricity and radiation pressure. The case of equal radiation factors of the two primaries is considered and the full range of values of the common radiation factor is explored, from the caseq
1 =q
2 =q = 1/8 at which the triangular equilibria disappear by coalescing on the rotating axis of the primaries transferring their stability to the collinear point, down toq = 0 at which value the stability regions in theµ - e plane disappear by shrinking down to zero size. It is found that radiation pressure exerts a significant influence on the stability regions. For certain intervals of radiation values these regions become qualitatively different from the gravitational case as well as the solar system case. They evolve as in the case of the triangular equilibrium point considered in a previous paper. There exist values of the common radiation factor, in the range considered, for which the collinear equilibrium point is stable for the entire range of mass distribution among the primaries and for large eccentricities of their orbits. 相似文献
16.
S. Hughes 《Planetary and Space Science》1977,25(9):809-815
An expression is derived for the solar radiation pressure disturbing function on an Earth satellite orbit which takes into account the variation of the solar radiation flux with distance from the Sun's centre and the absorption of radiation by the satellite. This expression is then expanded in terms of the Keplerian elements of the satellite and solar orbits using Kaula's method. The Kaula inclination functions are replaced by an equivalent set of modified Allan inclination functions.The resulting expression reduces to the form commonly used in solar radiation pressure perturbation studies (e.g. Aksnes, 1976), when certain terms are neglected. If, as happens quite often in practice, a satellite's orbit is in near-resonsnce with certain of these neglected terms, these near-resonant terms can cause changes in the satellite's orbital elements comparable to those produced by the largest term in Aksnes's expression. A new expression for the solar radiation pressure disturbing function expansion is suggested for use in future studies of satellite orbits perturbed by solar radiation pressure. 相似文献
17.
Krishna M. V. Apparao S. P. Tarafdar R. P. Verma K. V. K. Iyengar K. K. Ghosh 《Journal of Astrophysics and Astronomy》1993,14(3-4):131-134
The observed infrared excess in Be stars is usually interpreted as free-free and free-bound emission from a hot gas envelope
around the Be star. This hot gas should also emit H-alpha line radiation. Earlier observations had suggested that the infrared
excess and Hα radiation were not consistent with models in which they arise from the same ionized region; however the observations
were made at different times. We have made simultaneous observation of infrared and H-alpha line radiation. Our observations
imply that either both these radiations cannot arise from the same hot gas or additional processes have to be invoked to account
for the observed excess infrared radiation. 相似文献
18.
Ajoy Kumar Dasgupta 《Astrophysics and Space Science》1979,62(1):241-243
Transition radiation is emitted when a charged particle traverses a boundary separating two media. Such radiation must therefore be emitted as X-rays and ultraviolet radiation, from a medium where cosmic-ray electrons pass through dust grains. Calculation shows that transition radiation emitted in this way might account for soft X-rays emission from relativistic charged dust grains in the intergalactic medium (IGM). This could be a help in understanding the IGM as well as an indirect method of measuring the energies of high energy particles. 相似文献
19.
《New Astronomy》2013
We investigate the effect of mass on the radiation of a relativistically rotating neutron star. The method of Haxton and Ruffini is used to find the radiation flux from a relativistically rotating neutron star. By extending the idea of a point charge orbiting a black hole, a pulsar is modeled by simulating a relativistically rotating magnetic dipole embedded within a neutron star. The resulting equations retain the mass of the neutron star, thereby introducing effects of general relativity on the radiation from the dipole. We present exact solutions to the modeling equation as well as plots of energy spectra at different rotational velocities and inclination angles. We also present plots of total energy versus mass and two tables containing a comparison of energy ratios. These demonstrate that, for realistic neutron star masses, the high speed enhancement of the radiation is always more than compensated by the frame dragging effect, leading to a net reduction of radiation from the star. It is found that the inclusion of mass not only reduced the special relativistic enhancement, but negates it entirely as the mass of the neutron star approaches the mass limit. 相似文献
20.
It is shown that an outgoing null radiation field in the outer space of a Kerr-Newman black hole is darkened by the rotation
of the black hole. This rotational darkening is calculated for a spheroid emitting null radiation normally to its surface,
yielding the von Zeipel-like effectthat the equatorial region is darkened more strongly than the polar regions.This effect
is not confined to the case of black holes but is also observable for relativistically rotating fluid spheroids such as atmospheres
of pulsars or neutron stars. Moreover, application to Hawking radiation suggests that the black hole cannot be viewed as a
classical black body but that the Hawking radiationis a global geometric effect.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献