首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 31 毫秒
1.
We develop here theoretical relations between fluctuations of airglow brightness, fluctuations of temperature as revealed by airglow, and the atmospheric gravity waves that are believed to cause these fluctuations. We note and account for differences between our relations and those obtained by Krassovsky (1972, Ann. Geophys. 28, 739) and Weinstock (1978, J. geophys. Res. 83, 5175), correcting both of the latter in the process. We explicitly repudiate the need for a nonlinear treatment of O2(1Σg) emissions as it was asserted by Weinstock, one aspect of the nonlinear treatment he gave, and the conclusions he drew from that treatment, including, inter alia, the conclusion that temperature fluctuations carry more meaning as a diagnostic than do brightness fluctuations. Instead, we note the dependence of both types of fluctuation on variable gravity-wave parameters, which dependence can be applied to the study of gravity waves via airglow or of airglow via gravity waves. As a first step, we note the ability of the present analysis to account for certain observations of OH and O2(1Σg) emissions that have been, until now, inadequately or incorrectly explained, and we stress the importance of the proper measurement of parameters such as wave frequency and propagation speed if our own tentative explanations are to be put to the test and further progress is to be made.  相似文献   

2.
《Icarus》1987,70(1):111-123
Measurements of total yields, temperature dependences, mass spectra, and energy spectra of molecules sputtered from condensed sulfur (S8) at low temperatures by keV ions are reported and results are given for Jovian plasma ion bombardment of Io. A change in the reflectance of the sulfur, which can be removed by annealing, is produced by the most penetrating ions and may be connected with the darker, colder polar regions on Io. The measured sputtering yields are much lower than those estimated earlier for room temperature sulfur films but are comparable to previous measurements of keV ion sputtering of SO2 at low temperatures. The corrected mass spectrum indicates that ≈66% of the total yield corresponds to S2 ejection while only 5 and 16% correspond to S and S3, respectively. Therefore, if ions reach the surface of Io its atmosphere will have a non-negligible sulfur component of primarily S2. The ejection of S and S2 is temperature independent for temperatures characteristic of most of the surface of Io. The energy spectrum for S has an approximate 1/E2 dependence at high ejection energies, whereas S2 and S3 fall off more rapidly. Assuming 50% coverage of both sulfur and SO2 and a thin atmosphere (e.g., nightside and polar region) the direct sputter injection of sulfur atoms and molecules into the Jovian plasma torus and the indirect injection due to coronal processes are estimated. These injection rates for sulfur are compared to those for SO2 showing that injection from sulfur deposits contributes 13% to the total mass injection rate of ∼2–3 × 1029 amu/sec.  相似文献   

3.
We observed Saturn at far-infrared and submillimeter wavelengths during the Earth's March 1980 passage through the plane of Saturn's rings. Comparison with earlier spectroscopic observations by D. B. Ward [Icarus32, 437–442 (1977)], obtained at a time when the tilt angle of the rings was 21.8°, permits separation of the disk and ring contributions to the flux observed in this wavelength range. We present two main results: (1) The observed emission of the disk between 60 and 180 μm corresponds to a brightness temperature of 104 ± 2°K; (2) the brightness temperature of the rings drops approximately 20°K between 60 and 80 μm. Our data, in conjunction with the data obtained by other observers between 1 μm and 1 mm, permit us to derive an improved estimate for the total Saturnian surface brightness of (4.84 ± 0.32) × 10?4W cm?2 corresponding to an effective temperature of 96.1 ± 1.6°K. The ratio of radiated to incident power, PR/PI, is (1.46 ± 0.08)/(1 - A), where A is the Bond albedo. For A = 0.337 ± 0.029, PR/PI = 2.20 ± 0.15 and Saturn's intrinsic luminosity is LS = (2.9 ± 0.5) × 10?10L⊙.  相似文献   

4.
The astrophysical S-factor for 4He-3He radiative capture is calculated at very low-energies. We construct conserved two- and three-body electromagnetic currents, using minimal substitution in the explicit momentum dependence of the two- and three-cluster interactions. The realistic Argonne v 18 two-nucleon and Urbana IX or Tucson-Melbourne three-cluster interactions are considered for calculation. The zero energy S-factor is found to be S(0)=0.563 (0.581) keV?b, with (without) three-body interactions, in satisfactory agreement with other theoretical results and experiment data.  相似文献   

5.
Régis Courtin 《Icarus》1982,51(3):466-475
The pressure-induced absorptions of gaseous nitrogen (N2) and methane (CH4) are computed on the basis of the collisional lineshape theory of G. Birnhaum and E.R. Cohen [Canad. J. Phys.54, 593–602 (1976)]. Laboratory data at 300 and 124°K for N2 and at 296 and 195°K for CH4 are used to determine the collisional time constant and their temperature dependence. The spectrum of Titan from the microwave to the far-infrared region (0.1–600 cm?1) is then modeled using these opacities and a temperature profile of Titan's atmosphere derived from the Voyager 1 radio occultation experiment. The model atmosphere is composed of N2 and CH4, their relative proportions being determined by the vapor pressure law of CH4. A model with gaseous opacity alone is ruled out by the far-infrared observations. An additional opacity, thought to be associated with a methane cloud, is confirmed. The effective temperature of Titan is estimated at Te = 83.2 ± 1.4°K.  相似文献   

6.
The galactic dynamical system expressed by a third-order axisymmetric polynomial potential is investigated numerically by computing periodic solutions. We define as Sthe compact set of initial conditions generating bounded motions, and as S p , with S p ? S, the countable set of all initial conditions generating periodic solutions. Then, we consider the subsets S s p and S a p of S p , where S s p ∪ S a p = S p , S s p S a p = Ø, the first of which corresponds to symmetric periodic solutions, and the second to asymmetric solutions. Then, we approximate the set S s p , leaving treatment of the set S a p of asymmetric solutions for a future publication. The set S s p is known to be dense in S (‘Last Geometric Theorem of Poincar;’, Birkhoff, 1913). Using a computer programme capable to locate all elements of the set S s p that generate symmetric periodic solutions that re-enter after intersecting the axis of symmetry from 1 to ntimes. The results of the approximation of S s p in the total domain and in the sample sub-domains of zooming, we present in graphical form as family curves in the (x, C) plane. The solutions located with the largest periods re-enter after 440 galaxy revolutions while the families calculated fully (initial conditions, period, energy, stability co-efficient) include solutions that re-enter after 340 galaxy revolutions. To advance further the approximation of the set S s p thus obtained, we applied the same procedure inside eight sub-domains of the domain Sinto which we ‘zoomed’ through selection of finer search steps and double maximum periods. The family curves thus calculated presented in the (x, C) plane do not intersect anywhere in some sub-domains and their pattern resembles that of laminar flow. In other sub-domains, however, we found family curves from which branching families emanate. The concepts of completeand non-completeapproximation of S s p in sub-domains of laminar and sub-domains with branching family curves, respectively, is introduced. Also, the concept of basic family of order1, 2, ..., n, are defined. The morphology of individual periodic solutions of all families is investigated, and the types of envelopes found are described. The approximate set S s p was also checked by computing Poincar; sections for energy values corresponding to the mean energy range of the eight sub-domains of zooming mentioned above. These sections show that most parts of the compact domain in Sgenerating non-periodic but bounded solutions correspond to with well-shaped tori that intersect the x-axis, a fact that implies that dominant to exclusive type of periodic solutions are the symmetric ones with two normal crossings of this axis. The presence of non-symmetric periodic solutions as well as of chaotic regions is encountered. All calculations reported here were performed using the variable step R-K 8th-order direct integration and setting the allowable energy variation Δ C= |C start? C end| < 10?13. The output, consisting of many thousands of families and their properties (initial conditions, morphology, stability, etc.), is stored in a directory entitled ‘Atlas of the Symmetric Periodic Solution of the Galactic Motion Problem’.  相似文献   

7.
Stratospheric temperature profiles of Uranus were derived from the stellar occultation of 22 April 1982 in the pressure range 5–30 μbar. The observations were made at the European Southern Observatory, Chile, and at the Observatoire du Pic du Midi et de Toulouse, France with two telescopes in both sites. The study of these profiles confirms that Uranus' stratosphere is warmer than had been expected from radiative models (J. F. Appleby, 1980, Atmospheric Structures of the Giant Planets from Radiative-Convective Equilibrium Models. PhD. Thesis, State University of New York at Stony Brook) and that there has been a general increase of temperature since 1977 (R. G. French, J. L. Elliot, E. W. Dunham, D. A. Allen, J. H. Elias, J. A. Frogel, and W. Liller, 1983, Icarus53, 399–414). Furthermore, the profiles exhibit a nonisothermal feature with a maximum temperature around the 8-μbar pressure level. The amplitude of this feature increases linearly with the diurnally averaged insolation 〈D〉 up to the observed value 〈D〉 ～ 0.15. Moreover, the temperature at 8 μbar, as well as the mean stratospheric temperature, reaches a plateau around the equator of the planet which is far from maximum insolation. For a nominal abundance of methane ηCH4 ～ 3 × 10?5 and normal incidence, the UV absorption could compete with the IR methane absorption bands at the pressure level 8 μbar. However, the high temperatures observed even at grazing incidence imply important circulation phenomena to isothermalize distant regions of the planet. Alternatively, the observed profiles may suggest that an optically thin aerosol layer distributed over one scale height is responsible for the temperature maximum at 8 μbar. The total mass of dust necessary to heat this region up significantly would be a small fraction (6 × 1010 g vs 5 × 1018 g) of the Uranian ring system, which appears then as a possible reservoir of dust. However, a falling rate of ～1 msec?1 would deplete the rings in a short time (≈2 × 105 years) so that a dynamical process is needed to sustain the aerosol layer.  相似文献   

8.
A variety of astronomical phenomena appear to not satisfy the ergodic hypothesis in the relevant stationary state, if any. As such, there is no reason for expecting the applicability of Boltzmann–Gibbs (BG) statistical mechanics. Some of these phenomena appear to follow, instead, nonextensive statistical mechanics. In the same manner that the BG formalism is based on the entropy S BG=?k∑ i p i ln p i, the nonextensive one is based on the form S q=k(1 ?∑ i p i q)/(q? 1) (with S 1=S BG). The stationary states of the former are characterized by an exponential dependence on the energy, whereas those of the latter are characterized by an (asymptotic) power law. A brief review of this theory is given here, as well as of some of its applications, such as the solar neutrino problem, polytropic self-gravitating systems, galactic peculiar velocities, cosmic rays and some cosmological aspects. In addition to these, an analogy with the Keplerian elliptic orbits versus the Ptolemaic epicycles is developed, where we show that optimizing S q with a few constraints is equivalent to optimizing S BG with an infinite number of constraints.  相似文献   

9.
Ground-based observations of the occultation of ? Gem by Mars on April 8, 1976 have been reduced in the manner of French et al. [Icarus 33, 186–202 (1978)] to yield the scale height and temperature profiles of the Martian atmosphere for number densities between 1013 and 1015 cm?3. The deduced variations in temperature are remarkably similar to those obtained by Elliot et al. [Astrophys. J.217, 661–679 (1977)] and to the in situ measurements from the Viking landers.  相似文献   

10.
The unexpectedly large scale height of Io's ionosphere (Kliore, A., et al., 1975, Icarus24, 407–410) together with the relatively large molecular weight of the likely principal constituent, SO2 (Pearl, J., et al., 1979, Nature280, 755–758), suggest a high ionospheric temperature. Electrical induction in Io's ionosphere due to the corotating plasma bound to the Jovian magnetosphere is one possible source for attainment of such high temperatures. Accordingly, unipolar induction models were constructed to calculate ionospheric joule heating numerically. Heating rates produced by highly simplified models lie in the range 10?9 to 10?8 W/m3. These heating rates are lower than those determined from uv photodissociative heating models (Kumar, S., 1980, Geophys. Res. Lett.7, 9–12) at low levels in the ionosphere but are comparable in the upper ionosphere. The low electrical heating rate throughout most of the ionosphere is due to the power limitation imposed by the Alfvén wings which complete the electrical circuit (Neubauer, F.M., 1980, J. Geophys. Res.85, 1171–1178). Contrary to the pre-Voyager calculations of Cloutier, P. A., et al. (1978, Astrophys. Space Sci.55, 93–112), our numerical results show that the J × B force density due to unipolar induction currents in the ionosphere is much less than the gravitational force density when the combined mass of the neutral species is included. The binding and coupling of the ionosphere is principally due to the relatively dense (possibly localized) neutral SO2 atmosphere. In regions where the ions and neutrals are collisionally coupled the ionosphere will not be stripped off by the J × B forces. However at a level above that (to which the ions move by diffusion only) the charged species would be removed. Thus there appears to be no need to postulate the existence of an intrinsic Ionian magnetic field as suggested by Kivelson, M. G., et al. (79, Science 205, 491–493) and Southwood, S. J., et al. (1980, J. Geophys. Res., in press) in order to retain the observed ionosphere.  相似文献   

11.
The population densities of all levels with principal quantum numbern=2 in a number of helium-like ions with nuclear charge numberZ, in the range 6 to 28 have been evaluated as a function of various parameters, i.e., electron temperature,T e, electron density,N e, radiation temperature,T r, dilution factor,W, and of the state of ionization. The spectral line fluxes from all possible radiative transitions from these levels have been calculated for an optically thin plasma. The effects of cascades following collisional excitation of higher levels or radiative and dielectronic recombination have been computed in detail. Innershell ionization of the lithium-like ion to form the helium-like ion in a 23 S or 21 S state has been considered. It can have a strong influence on the forbidden line intensity in a non-equilibrium plasma. Collisional and radiative coupling of levels of the same multiplicity (e.g. 23 S 1 and 23 P 2,1,0) have been considered as a function ofT e, Ne orT r, W, respectively. The computations were performed both for stationary and time-varying plasmas. In the latter case strong departures from a stationary ionization equilibrium can significantly alter the line fluxes. A few examples of the results are shown and discussed.  相似文献   

12.
In a previous paper (Cosmic Electrodyn.3, 116) we had suggested the use of the radialr ?2/5 dependence rather than the often usedr ?2/7 one in approximations of the electronic temperature profile in some two-fluid models. This note is intended to clarify and restate some points on this subject.  相似文献   

13.
A four-parameter model which assumes a Gaussian dependence of both temperature and pressure on distance from center is used to fit the compact part of coronal active regions as observed in X-ray photographs from a rocket experiment. The four parameters are the maximum temperature T M, the maximum pressure P M= 2NMkTM, the width of the pressure distribution σ P, and the width of the temperature distribution σ T = α1/2σP. The maximum temperature T M ranges from 2.2 to 2.8 × 106K, and the maximum density N M from 2 to 9 × 109cm?3. The range of σ P is from 2 to 4 × 109 cm and that of α from 2 to 7.  相似文献   

14.
We considered three modes of black hole formation: (I) a black hole kernel first forms at the centre of a collapsing star and as the outer matter falls, the kernel grows until the whole star becomes a black hole; (II) all the layers of a collapsing simultaneously satisfy the Schwarzschild condition; (III) the outermost layer first satisfies the Schwarzschild condition. For each mode, we calculated the entropy carried by the collapsing matter, Sm, and the entropy of the black hole so formed, SBH. We found SBH to be 1019 times Sm and the lower limit of the mass capable of becoming a black hole to be the Planck mass, Mp = 10?5g. A discussion on the nature of SBH led us to think that SBH possibly contains things other than the ordinary thermodynamical entropy.  相似文献   

15.
Statistical analyses of solar radio observations have shown that proton events are likely to occur when the flux at 3 cm, S3, of the SVC is greater than 25 sfu and when S3/S8 is grater than 1. A theoretical explanation of this fact is attempted in this paper. I calculated the spectrum of the SVC using the gyro-radiation emission and found that the main reason for S3 >; 25sfu is a ten-fold increase in the conductive energy flux in the active region over the quiet region, raising the height of the gyro-resonance layer for the 3 cm emission, and that the main reason for S3/S8 ? 1 is an increase in the coronal magnetic field gradient in the active region, causing a decrease in the optical thickness for the gyro-resonance absorption at 3 cm. It is precisely these active regions that are most favourable for the production of proton events.  相似文献   

16.
In the framework of the MOdified Newtonian Dynamics (MOND), the internal dynamics of a gravitating system s embedded in a larger one S is affected by the external background field E of S even if it is constant and uniform, thus implying a violation of the Strong Equivalence Principle: it is the so-called External Field Effect (EFE). In the case of the solar system, E would be A cen≈10?10 m?s?2 because of its motion through the Milky Way: it is orders of magnitude smaller than the main Newtonian monopole terms for the planets. We address here the following questions in a purely phenomenological manner: are the Sun’s planets affected by an EFE as large as 10?10 m?s?2? Can it be assumed that its effect is negligible for them because of its relatively small size? Does E induce vanishing net orbital effects because of its constancy over typical solar system’s planetary orbital periods? It turns out that a constant and uniform acceleration, treated perturbatively, does induce non-vanishing long-period orbital effects on the longitude of the pericenter ? of a test particle. In the case of the inner planets of the solar system and with E≈10?10 m?s?2, they are 4–6 orders of magnitude larger than the present-day upper bounds on the non-standard perihelion precessions \(\Delta\dot{\varpi}\) recently obtained with by E.V. Pitjeva with the EPM ephemerides in the Solar System Barycentric frame. The upper limits on the components of E are E x ≤1×10?15 m?s?2, E y ≤2×10?16 m?s?2, E z ≤3×10?14 m?s?2. This result is in agreement with the violation of the Strong Equivalence Principle by MOND. Our analysis also holds for any other exotic modification of the current laws of gravity yielding a constant and uniform extra-acceleration. If and when other corrections \(\Delta\dot{\varpi}\) to the usual perihelion precessions will be independently estimated with different ephemerides it will be possible to repeat such a test.  相似文献   

17.
The rates of momentum and energy transfer have been obtained for charge exchange collisions between ion and neutral gases having arbitrary Maxwellian temperatures Ti and Tn and bulk transport velocities ci and cn. The results are directly applicable to the F-region of the ionosphere where O+ - O charge is the dominant mechanism affecting ion momentum and energy transfer.  相似文献   

18.
P. Persi 《Solar physics》1975,43(1):39-47
A new numerical method for the analysis of the high dispersion photospheric spectrum is described. In particular the method is applied to study the C2(0, 0) d 3 Πg-a a Πu molecular band. From measurements of the equivalent widths of C2 lines, a rotational temperature of 4450 ± 305 K is obtained, and the band intensity log W 0 /S 0 = ?0.051 ± 0.101 is found.  相似文献   

19.
We have analyzed spectra of CO recorded with the instrument PFS onboard Mars Express in the (1-0) band. The dataset we used ranges in time from January until June 2004 (LS=331°.17 until LS=51°.61; end of Mars Year 26, beginning of Mars Year 27). The aim of this work was to determine the amplitude of the CO mixing ratio departures from the mean globally averaged value currently admitted (8±3×10-4) [Kaplan, L.D., Connes, J., Connes, P., 1969. Carbon monoxide in the martian atmosphere. Astron. J. 157, L187-L192] as a function of season, local time and location on the planet. We therefore processed the data from 90 calibrated orbits. The globally averaged CO mixing ratio value we derive from our dataset, 11.1×10-4, is compatible with the range found by Kaplan et al. [1969. Carbon monoxide in the martian atmosphere. Astron. J. 157, L187-L192], although somewhat higher than the “standard” value. However, the CO mixing ratio we retrieve exhibits large variations (roughly between 3×10-4 and 18×10-4). Such relative variations have been used on a statistical basis to derive main trends as a function of latitude for three LS ranges: 331-360°, 0-30° and 30-52°. For the first LS range, we seem to have an enhancement of the CO mixing ratio towards the northern latitudes, probably linked to the CO2 condensation in winter on the north polar cap. The situation for the two other LS ranges is not so clear, mainly as we lack data on the southern hemisphere. We roughly agree with the work of Krasnopolsky [2007. Long-term spectroscopic observations of Mars using IRTF/CSHELL: mapping of O2 dayglow, CO and search for CH4. Icarus 190, 93-102] for LS=331-360°, thus confirming the effect of seasonal condensation of CO2 on the north polar cap, but we have no agreement for other seasons.  相似文献   

20.
The temperature dependence of the binary recombination coefficient, α2, for the reaction NO++NO2? → products has been obtained over the range 185–530 K. It is found that the corresponding mean cross section σ is described by the power law σ ? A · T?0.9, and that α2 ? B · T?0.4. Data has also been obtained for two cluster ion recombination reactions which indicate that their recombination cross sections are only about 40% larger than for the parent ions at a given temperature, the cross sections for these reactions also apparently increasing with decreasing temperature. In the light of this data and by considering the most probable positive and negative ions existing at various altitudes up to 90km in the atmosphere, the most appropriate ionic recombination coefficients in various altitude ranges are deduced. Thus, between 30 and 90 km, where the recombination process is two-body, the coefficient varies over the narrow range 5–9 × 10?8 cm3s?1, while below 30 km the process is predominantly three-body with an effective two-body rate increasing rapidly to a maximum value ≈3 × 10?6 cm3s?1 in the troposphere, these deductions being based on published laboratory determinations of three-body recombination coefficients.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号