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1.
Using the explicit form of the functions to describe the monopole and dipole spectra of the Cosmic Microwave Background (CMB) radiation, the exact expressions for the temperature dependences of the radiative and thermodynamic functions, such as the total radiation power per unit area, total energy density, number density of photons, Helmholtz free energy density, entropy density, heat capacity at constant volume, and pressure in the finite range of frequencies v 1≤v≤v 2 are obtained. Since the dependence of temperature upon the redshift z is known, the obtained expressions can be simply presented in z representation. Utilizing experimental data for the monopole and dipole spectra measured by the COBE FIRAS instrument in the 60–600 GHz frequency interval at the temperature T=2.72548 K, the values of the radiative and thermodynamic functions, as well as the radiation density constant a and the Stefan-Boltzmann constant σ are calculated. In the case of the dipole spectrum, the constants a and σ, and the radiative and thermodynamic properties of the CMB radiation are obtained using the mean amplitude T amp=3.358 mK. It is shown that the Doppler shift leads to a renormalization of the radiation density constant a, the Stefan-Boltzmann constant σ, and the corresponding constants for the thermodynamic functions. The expressions for new astrophysical parameters, such as the entropy density/Boltzmann constant, and number density of CMB photons are obtained. The radiative and thermodynamic properties of the Cosmic Microwave Background radiation for the monopole and dipole spectra at redshift z≈1089 are calculated.  相似文献   

2.
A model calculation to predict infrared Shuttle flow due to the radiative relaxation of vibration of the NO molecule is presented. Space Shuttles hit atmospheric NO molecules at a very high speed (≈ 8 km s?1) and excite vibrational and rotational motions up to the temperature of 54,000 K. With the electric dipole radiation of Δν = 1, 2, 3, and particularly 4 (ν is the vibrational quantum number), the excited NO molecules emit infrared radiation before they collide with other molecules. The total radiation power is estimated to be 170AμW, where A is the cross-section area of the Shuttle in m2 if no adsorption of the NO molecule takes place on the Shuttle surface. The intensity of each infrared line is calculated as a function of time, including all vibrational states up to ν = 35. For example, the 5039 cm?1 line (ν = 24 → 20) has a maximum intensity of about 2.3 × 10?21 W molecule at around 0.2 ms, which corresponds to 80 cm from the Shuttle surface if the recoil speed of the molecules is 4 km s?1.  相似文献   

3.
Degeneracy effects for bosons are more important for smaller particle mass, smaller temperature and higher number density. Bose condensation requires that particles be in the same lowest energy quantum state. We propose a cosmic background Bose condensation, present everywhere, with its particles having the lowest quantum energy state, ?c/λ, with λ about the size of the visible universe, and therefore unlocalized. This we identify with the quantum of the self gravitational potential energy of any particle, and with the bit of information of minimum energy. The entropy of the universe (～10122 bits) has the highest number density (～1036 bits/cm3) of particles inside the visible universe, the smallest mass, ～10?66 g, and the smallest temperature, ～10?29 K. Therefore it is the best candidate for a Cosmic Background Bose Condensation (CBBC), a completely calmed fluid, with no viscosity, in a superfluidity state, and possibly responsible for the expansion of the universe.  相似文献   

4.
The Picard spacecraft was successfully launched on 15 June 2010, into a Sun-synchronous orbit. The mission represents one of the European contributions to solar observations and Essential Climate Variables (ECVs) measurements. The payload is composed of a Solar Diameter Imager and Surface Mapper (SODISM) and two radiometers: SOlar VAriability Picard (SOVAP) and PREcision MOnitor Sensor (PREMOS). SOVAP, a dual side-by-side cavity radiometer, measures the total solar irradiance (TSI). It is the sixth of a series of differential absolute-radiometer-type instruments developed and operated in space by the Royal Meteorological Institute of Belgium. The measurements of SOVAP in the summer of 2010 yielded a TSI value of 1362.1 W?m?2 with an uncertainty of ±?2.4 W?m?2 (k=1). During the periods of November 2010 and January 2013, the amplitude of the changes in TSI has been on the order of 0.18 %, corresponding to a range of about 2.4 W?m?2.  相似文献   

5.
Two-deuteron radiative capture reaction is one of the deuterium-burning processes that the cross section is not well known at very low-energies. We develop the formalism based on pionless Effective Field Theory (EFT) for deuteron–deuteron (dd) scattering to derive the cross section of two-deuteron radiative capture. Within this formalism the two- and three-body forces, should also be included in the capture cross section calculations. The aim of the present work is to calculate the observables of the low-energy dd photonuclear reactions. The cross section and the astrophysical S-factor for the 2H(d,γ)4He reaction have been calculated. The 4He is studied as four-body bound states in the pionless EFT. The theoretical uncertainties for observables are estimated based on the variation of the cutoffs. The astrophysical S-factor is accurately determined to be 6.9×10?6 keV?b (6.1×10?6 keV?b) for two-body (two- and three-body) at zero energy. A satisfactory agreement between theory and experiment for dd radiative capture observables up to order of calculation has been found by insertion of three-body force.  相似文献   

6.
The transport of energy in space plasmas, especially in the solar wind, is far from being understood. Measuring the temperature of the electrons and their non-thermal properties is essential to understand the transport properties in collisionless plasmas. Quasi-thermal noise spectroscopy is a reliable tool for measuring the electron temperature accurately since it is less sensitive to the spacecraft perturbations than particle detectors. We apply this method to Ulysses radio data obtained during the first pole-to-pole fast latitude scan in the high-speed solar wind, using a kappa function to describe the electron velocity distribution. We deduce the variations with heliocentric distance between 1.5 and 2.3 AU in the fast solar wind at high latitude in terms of three fitting parameters: the electron density varies as n e??R ?1.96±0.08, the electron temperature as T e??R ?0.53±0.15, and the kappa index of the distribution remains constant at ??=2.0±0.2. These observations agree with the predictions of the exospheric theory.  相似文献   

7.
We provide our estimates of the intensity of the gamma-ray emission with an energy near 0.1 TeV generated in intergalactic space in the interactions of cosmic rays with background emissions. We assume that the cosmic-ray sources are pointlike and that these are active galactic nuclei. The following possible types of sources are considered: remote and powerful ones, at redshifts up to z = 1.1, with a monoenergetic particle spectrum, E = 1021 eV; the same objects, but with a power-law particle spectrum; and nearby sources at redshifts 0 < z ≤ 0.0092, i.e., at distances no larger than 50 Mpc also with a power-law particle spectrum. The contribution of cosmic rays to the extragalactic diffuse gammaray background at an energy of 0.1 TeVhas been found to depend on the type of sources or, more specifically, the contribution ranges from f ? 10?4 to f ≈ 0.1, depending on the source model. We conclude that the data on the extragalactic background gamma-ray emission can be used to determine the characteristics of extragalactic cosmic-ray sources, i.e., their distances and the pattern of the particle energy spectrum.  相似文献   

8.
Strong (B?109 G) and superstrong (B?1014 G) magnetic fields profoundly affect many thermodynamic and kinetic characteristics of dense plasmas in neutron star envelopes. In particular, they produce strongly anisotropic thermal conductivity in the neutron star crust and modify the equation of state and radiative opacities in the atmosphere, which are major ingredients of the cooling theory and spectral atmosphere models. As a result, both the radiation spectrum and the thermal luminosity of a neutron star can be affected by the magnetic field. We briefly review these effects and demonstrate the influence of magnetic field strength on the thermal structure of an isolated neutron star, putting emphasis on the differences brought about by the superstrong fields and high temperatures of magnetars. For the latter objects, it is important to take proper account of a combined effect of the magnetic field on thermal conduction and neutrino emission at densities ρ?1010 g?cm?3. We show that the neutrino emission puts a B-dependent upper limit on the effective surface temperature of a cooling neutron star.  相似文献   

9.
Our knowledge of the high-energy universe is undergoing a period of rapid change as new astronomical detectors of high-energy radiation start to operate at their design sensitivities. Now is a boomtime for high-energy astrophysics, with new discoveries from Swift and HESS, results from MAGIC and VERITAS starting to be reported, the upcoming launches of the γ-ray space telescopes GLAST and AGILE, and anticipated data releases from IceCube and Auger. A formalism for calculating statistical properties of cosmological γ-ray sources is presented. Application is made to model calculations of the statistical distributions of γ-ray and neutrino emission from (i) beamed sources, specifically, long-duration GRBs, blazars, and extragalactic microquasars, and (ii) unbeamed sources, including normal galaxies, starburst galaxies and clusters. Expressions for the integrated intensities of faint beamed and unbeamed high-energy radiation sources are also derived. A toy model for the background intensity of radiation from dark-matter annihilation taking place in the early universe is constructed. Estimates for the γ-ray fluxes of local group galaxies, starburst, and infrared luminous galaxies are briefly reviewed. Because the brightest extragalactic γ-ray sources are flaring sources, and these are the best targets for sources of PeV–EeV neutrinos and ultra-high energy cosmic rays, rapidly slewing all-sky telescopes like MAGIC and an all-sky γ-ray observatory beyond Milagro will be crucial for optimal science return in the multi-messenger age.  相似文献   

10.
The extragalactic background radiation produced by distant galaxies emitting in the far infrared limits the sensitivity of telescopes operating in this range due to confusion. We have constructed a model of the infrared background based on numerical simulations of the large-scale structure of the Universe and the evolution of dark matter halos. The predictions of this model agree well with the existing data on source counts. We have constructed maps of a sky field with an area of 1 deg2 directly from our simulated observations and measured the confusion limit. At wavelengths 100–300 μm the confusion limit for a 10-m telescope has been shown to be at least an order of magnitude lower than that for a 3.5-m one. A spectral analysis of the simulated infrared background maps clearly reveals the large-scale structure of the Universe. The two-dimensional power spectrum of these maps has turned out to be close to that measured by space observatories in the infrared. However, the fluctuations in the number of intensity peaks observed in the simulated field show no clear correlation with superclusters of galaxies; the large-scale structure has virtually no effect on the confusion limit.  相似文献   

11.
To choose the best strategy for conducting a deep extragalactic survey with the ART-XC X-ray telescope onboard the Spectrum–Röntgen–Gamma (SRG) observatory and to estimate the expected results, we have simulated the observations of a 1.1° × 1.1° field in the 5–11 and 8–24 keV energy bands. For this purpose, we have constructed a model of the active galactic nuclei (AGN) population that reflects the properties of the X-ray emission from such objects. The photons that “arrived” from these sources were passed through a numerical model of the telescope, while the resulting data were processed with the standard ART-XC data processing pipeline. We show that several hundred AGNs at redshifts up to z ≈ 3 will be detected in such a survey over 1.2 Ms of observations with the expected charged particle background levels. Among them there will be heavily obscured AGNs, which will allow a more accurate estimate of the fraction of such objects in the total population to be made. Source confusion is expected at fluxes below 2 × 10?14 erg s?1 cm?2 (5–11 keV). Since this value can exceed the source detection threshold in a deep survey at low particle background levels, it may turn out to be more interesting to conduct a survey of larger area (several square degrees) but smaller depth, obtaining a sample of approximately four hundred bright AGNs as a result.  相似文献   

12.
Alpha radiative capture reactions offers the opportunity to study nuclear processes of astrophysical interest. Most of the existing data on these processes have been gained by means of gamma-ray spectroscopy, where the measurements are very difficult due to the low cross sections and the relatively high background in the detectors. We have calculated the two-alpha radiative capture process and excitations of 8Be nuclei interacting using current conservation realistic two- and three-nucleon potentials, at settler energies. We have presented the results of Faddeev-type calculations for current conservation of two- and three-body interactions to cluster nuclear reactions. Our results for cross sections are found to be 128 (140) nanobarn for the current conservation two-body (two-body and three-body) interactions, at the resonance energy with an 14 % (6 %) accuracy in comparison with the recent experimental data, respectively. The results for B (E2) value of 8Be is also found to be 21.7 (20.8) e 2 fm 4, in comparison with the very recent experimental data with an error of 7 % (2 %). Our calculation show that the bulk energies are corrected by improved few-body potentials.  相似文献   

13.
Having analyzed high-resolution observations of extragalactic compact radio sources with modern systems of radio telescopes, we obtained an estimate of the upper limit for the photon electric charge, eγ ? 3×10?33 of the elementary charge (assuming the photon charge to be energy independent). This is three orders of magnitude better than the limit obtained from radio pulsar timing. We also set a limit on the charge of a gamma-ray (energy ～0.1 MeV) photon. In the future, the estimate based on extragalactic sources can be improved significantly.  相似文献   

14.
Using the supplementary advances of the perihelia provided by INPOP10a (IMCCE, France) and EPM2011 (IAA RAS, Russia) ephemerides, we obtain preliminary limits on a logarithmic correction to the Newtonian gravitational potential in the solar system. This kind of correction may originate from fundamental frameworks, like string theories or effective models of gravity due to quantum effects and the non-local gravity scheme. We estimate upper limit of Tohline-Kuhn-Kruglyak parameter λ and lower bound of Fabris-Campos parameter α, which parametrize the correction and connect each other by αλ=?1. In our estimation, we take the Lense-Thirring effect due to the Sun’s angular momentum and the uncertainty of the Sun’s quadrupole moment into account. These two factors were usually absent in previous works. We find that INPOP10a yields the upper limit as α=?(0.66±5.82)×10?4 kpc?1 [or the lower limit as λ=(0.15±8.76)×105 kpc] while EPM2011 gives α=(0.52±1.74)×10?4 kpc?1 [or the lower limit as λ=?(0.19±3.29)×105 kpc]. The limits of |λ| are greater than the result based on the rotation curves of spiral galaxies by about 3 orders of magnitude, indicating its effects might be screened in high density regions.  相似文献   

15.
We construct the maps of temperatures, geometrical thicknesses, electron densities and gas pressures in a quiescent prominence. For this we use the RGB signal of the prominence visible-light emission detected during the total solar eclipse of 1 August 2008 in Mongolia and quasi-simultaneous Hα spectra taken at Ond?ejov Observatory. The method of disentangling the electron density and geometrical (effective) thickness was described by Jej?i? and Heinzel (Solar Phys. 254, 89?–?100, 2009) and is used here for the first time to analyse the spatial variations of prominence parameters. For the studied prominence we obtained the following range of parameters: temperature 6000?–?15?000 K, effective thickness 200?–?15000 km, electron density 5×109?–?1011 cm?3 and gas pressure 0.02?–?0.2 dyn?cm?2 (assuming a fixed ionisation degree n p/n H=0.5). The electron density increases towards the bottom of the prominence, which we explain by an enhanced photoionisation due to the incident solar radiation. To confirm this, we construct a two-dimensional radiative-transfer model with realistic prominence illumination.  相似文献   

16.
The r ?4 law of cold collapse has been explained in other work. Here we try to explain the density profile of mild relaxation by statistical mechanics. In this paper we first generate many kinds of initial conditions with the same mass and energy to see whether there are other initial factors that can change the density profile of an isolated equilibrium self-gravitating system; then for a more general initial condition we discuss the role of mass and energy in determining the final density profile. Next we use our previous results obtained from statistical mechanics to fit these simulations, and find that when the masses of the particles in clumps are less than 5 % of the total mass, or the initial density is shallower than r ?2, the whole virialized density profile (VDF) can be fitted well by our equation of state with three parameters, and some other cases can be explained by the theory with the r ?4 law. We conclude that statistical physics may play an important role in determining the shape of VDF in the mild relaxation, mass and energy can control the values of the central density and the system’s radius, but there are still other initial configurations that can affect the VDF.  相似文献   

17.
Based on the most complete list of the results of an individual comparison of the proper motions for stars of various programs common to the Hipparcos catalog, each of which is an independent realization of the inertial reference frame with regard to stellar proper motions, we redetermined the vector ω of residual rotation of the ICRS system relative to the extragalactic reference frame. The equatorial components of this vector were found to be the following: ωx=+0.04±0.15 mas yr?1, ωy=+0.18±0.12 mas yr?1, and ωz=?0.35±0.09 mas yr?1.  相似文献   

18.
The propagation and modulation of electrons in the heliosphere play an important part in improving our understanding and assessment of the modulation processes. A full three-dimensional numerical model is used to study the modulation of galactic electrons, from Earth into the inner heliosheath, over an energy range from 10 MeV to 30 GeV. The modeling is compared with observations of 6–14 MeV electrons from Voyager 1 and observations at Earth from the PAMELA mission. Computed spectra are shown at different spatial positions. Based on comparison with Voyager 1 observations, a new local interstellar electron spectrum is calculated. We find that it consists of two power-laws: In terms of kinetic energy E, the results give E ?1.5 below ～500 MeV and E ?3.15 at higher energies. Radial intensity profiles are computed also for 12 MeV electrons, including a Jovian source, and compared to the 6–14 MeV observations from Voyager 1. Since the Jovian and galactic electrons can be separated in the model, we calculate the intensity of galactic electrons below 100 MeV at Earth. The highest possible differential flux of galactic electrons at Earth with E=12 MeV is found to have a value of 2.5×10?1 electrons m?2?s?1?sr?1?MeV?1 which is significantly lower (a factor of 3) than the Jovian electron flux at Earth. The model can also reproduce the extraordinary increase of electrons by a factor of 60 at 12 MeV in the inner heliosheath. A lower limit for the local interstellar spectrum at 12 MeV is estimated to have a value of (90±10) electrons m?2?s?1?sr?1?MeV?1.  相似文献   

19.
V.A. Krasnopolsky 《Icarus》1979,37(1):182-189
Observations and model calculations of water vapor diffusion suggest that about half the amount of water vapor is distributed with constant mixing ratio in the Martian atmosphere, the other half is the excess water vapor in the lower troposphere. During 24 hr the total content of water vapor may vary by a factor of two. The eddy diffusion coefficient providing agreement between calculations and observations is K = (3–10) × 106 cm2 sec?1 in the troposphere. An analytical expression is derived for condensate density in the stratosphere in terms of the temperature profile, the particle radius r, and K. The calculations agree with the Mars 5 measurements for r = 1.5 μm, condensate density 5 × 10?12 g/cm3 in the layer maximum at 30 to 35 km, condensate column density 7 × 10?6 cm?2, K = (1?3) × 106 cm2 sec?1, and the temperature profile T = 185 ? 0.05z ? 0.01z2 at 20 to 40 km. Condensation conditions yield a temperature of 160°K at 60 km in the evening; the scale height for scattered radiation yields T = 110°k at 80 to 90 km. The Mars model atmosphere has been developed up to 125 km.  相似文献   

20.
Quasars, pulsars and other cosmic sources of intense radiation are known to have large brightness temperature (kT b?mc 2) and relativistic electron density values. In this case the induced Compton scattering by relativistic electrons should be considered. The probability of scattering with decreasing radiation frequency is derived for isotropic radiation scattering. When induced scattering takes place, the relativistic electron obtains its energy by transforming high-frequency quanta into the low-frequency ones. In the most intensive sources electrons would receive energiesE?mc 2 ××(kT b/mc 2)1/7 due to the heating rate proportional toE ?5 with the cooling rate proportional toE 2. Considerable distortion of the quasar spectrum is possible for reasonably large values of relativistic electron density (N?106cm?3) notwithstanding that the heating is negligible. In pulsars relativistic electron heating and spectrum distortion appear to depend more on the induced Compton scattering.  相似文献   

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