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1.
It is shown that the mean value for the heat flow of a gravitationally-differentiated Moon of fission origin is about 13 erg cm?2 s?1 and that the heat flow varies regionally from about 3 erg cm?2s?1 to more than 45 erg cm?2s?1. These regional variations in the heat flow are caused by a non-uniform distribution of K, U and Th in the KREEP zone at the crust-upper mantle boundary and the redistribution of crustal materials and K, U and Th rich KREEP materials by basin-forming impacts. The scale of these regional variations is hundreds of km. The models presented are in accord with the Apollo 15 and 17 heat flow measurements.  相似文献   

2.
Mid-infrared extinction coefficients of five natural amorphous silicates and seven synthetic glasses were measured. Three bands at about 10, 12, and 20 μm were seen for all the measured samples. The quantities of these bands are found to have good correlations with the SiO2 content of the samples. The correlations are the most remarkable for the 10 μm band. As the SiO2 content decreases, the peak wavelengthλ m shifts to longer side, the peak heightK m decreases and the full width of half maximumW increases. A quantityλ m K m W is constant within 15%. Empirical formula $$\lambda_m (\mu m) = {11.10-2.30 x 10^-2} {[SiO_2 wt.\%]} \pm 0.15$$ and $$W(\mu m) = {5.14-4.68 x 10^- 2} {[SiO_2 wt.\%]} \pm 0.30$$ are obtained for the measured samples. Therefore, the correlation is present between the 10 μm peak wavelengthλ m and peak widthW for amorphous silicates. The change in peak widthW is remarkable compared the change in peak wavelengthλ m as the SiO2 content varies. For the 12 μm band the correlations with the SiO2 content are not so good. A tendency that theλ m shifts to the red and theK m lowers as the decreasing SiO2 content are found. For the samples with SiO2 content less than 50% the 12 μm band cannot recognized as the peak. For the 20 μm band, theλ m is almost independent on SiO2 content and theK m lowers with decreasing SiO2 content. The results are compared with the observed 10 μm band of the astronomical objects. A method to estimate the SiO2 content of astronomical grain materials is proposed and 48±8% SiO2 wt.% is found corresponding to the peak wavelength of 9.7 μm and the peak width of 2.5–3.0 μm of typical celestial objects.  相似文献   

3.
The observations of VV Ori inUBV and inuvby obtained by Chambliss in 1975–79 have been re-analyzed with the use of an updated version of the WINK program of Wood. Several solutions were obtained using the normal points (ca. 80 per light curve). These establish fairly reliable values for the linear limb-darkening coefficient of VV Ori A and approximate values for the luminosity of the third component of this system. Attempts to determine non-linear coefficients of limb darkening for the primary component, however, proved to be unsuccessful. Solutions were also obtained using all observations (ca. 620 per light curve). Very close agreement was found between the values of the geometric elements determined from these solutions and those determined by use of the normal points only. The solutions based on all observations produced reliable values foru 1, the limb darkening coefficient of VV Ori A, (typically, 0.30±-0.04). These results are in good agreement with theoretical limb darkening coefficients derived from model atmospheres calculations. The contribution of VV Ori C to the light of the system was also ascertained, and it was found that this could be best interpreted, if this component has a spectral type of A3V. The other orbital elements of VV Ori were also discussed, and the differences between the various solutions were noted. Since VV Ori A is one of the very few early-type stars for which reliable limb-darkening coefficients can be empirically determined, this system is viewed as being of considerable importance.  相似文献   

4.
John A. Eddy 《Solar physics》1983,89(1):195-207
  相似文献   

5.
Lunar electric fields,surface Potential and Associated Plasma Sheaths   总被引：1，自引：0，他引：1  
This paper reviews the electric field environment of the Moon. Lunar surface electric potentials are reported as follows: Solar Wind - Dayside: øo + 10 to + 18 V Solar Wind - Terminator: øo ç ? 10 to ? 100 V Electron and ion densities in the plasma sheath adjacent to each surface potential regime are evaluated and the corresponding Debye length estimated. The electric fields are then approximated by the surface potential over the Debye length. The results are: Solar Wind - Dayside: Eo ? 10 V m?1 outward Solar Wind - Terminator: Eo ç 1 to 10 V m?1 inward These fields are all at least 3 orders of magnitude higher than the pervasive solar wind electric field; however they are confined to within a few tens of meters of the lunar surface.  相似文献   

6.
In this paper, the presence of Faraday rotation in measurements of the orientation of a sunspot's transverse magnetic field is investigated. Using observations obtained with the Marshall Space Flight Center's (MSFC) vector magnetograph, the derived vector magnetic field of a simple, symmetric sunspot is used to calculate the degree of Faraday rotation in the azimuth of the transverse field as a function of wavelength from analytical expressions for the Stokes parameters. These results are then compared with the observed rotation of the field's azimuth which is derived from observations at different wavelengths within the Fei 5250 Å spectral line. From these comparisons, we find: the observed rotation of the azimuth is simulated to a reasonable degree by the theoretical formulations if the line-formation parameter η o is varied over the sunspot; these variations in η o are substantiated by the line-intensity data; for the MSFC system, Faraday rotation can be neglected for field strengths less than 1800 G and field inclinations greater than 45°; to minimize the effects of Faraday rotation in sunspot umbrae, MSFC magnetograph measurements must be made in the far wings of the Zeeman-sensitive spectral line.  相似文献   

7.
The amplitude of the 11-year cycle measured in the cosmogenic isotope 10Be during the Maunder Minimum is comparable to that during the recent epoch of high solar activity. Because of the virtual absence of the cyclic variability of sunspot activity during the Maunder Minimum this seemingly contradicts an intuitive expectation that lower activity would result in smaller solar-cycle variations in cosmogenic radio-isotope data, or in none, leading to confusing and misleading conclusions. It is shown here that large 11-year solar cycles in cosmogenic data observed during periods of suppressed sunspot activity do not necessarily imply strong heliospheric fields. Normal-amplitude cycles in the cosmogenic radio-isotopes observed during the Maunder Minimum are consistent with theoretical expectations because of the nonlinear relation between solar activity and isotope production. Thus, cosmogenic-isotope data provide a good tool to study solar-cycle variability even during grand minima of solar activity.  相似文献   

8.
A. Duijveman  P. Hoyng 《Solar physics》1983,86(1-2):279-288
We review some recent advances in our understanding of impulsive solar flare phenomena obtained through new hard X-ray and radio imaging instruments (the Solar Maximum Mission and Hinotori satellites, the VLA and VLBI).  相似文献   

9.
This paper describes the detailed calibration at soft X-ray energies (0.1–2.0 keV; 125 Å-6 Å) of gold coated, paraboloidal X-ray mirrors, four of which were subsequently flow on the Ariel-6 satellite. Uncertainties in the attitude of the satellite together with an apparent reduction in sensitivity of the soft X-ray experiment necessitated observations using the Crab Nebula as a reference. These showed that a dramatic reduction in the reflection efficiencies of all four mirrors had occurred, almost certainly after or during launch. An initial recalibration of the mirrors using the Crab observation is described.  相似文献   

10.
A distinct magnetic cloud (MC) was observed in-situ at the Solar TErrestrial RElations Observatory (STEREO)-B on 20?–?21 January 2010. About three days earlier, on 17 January, a bright flare and coronal mass ejection (CME) were clearly observed by STEREO-B, which suggests that this was the progenitor of the MC. However, the in-situ speed of the event, several earlier weaker events, heliospheric imaging, and a longitude mismatch with the STEREO-B spacecraft made this interpretation unlikely. We searched for other possible solar eruptions that could have caused the MC and found a faint filament eruption and the associated CME on 14?–?15 January as the likely solar source event. We were able to confirm this source by using coronal imaging from the Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI)/EUVI and COR and Solar and Heliospheric Observatory (SOHO)/Large Angle and Spectrometric Coronograph (LASCO) telescopes and heliospheric imaging from the Solar Mass Ejection Imager (SMEI) and the STEREO/Heliospheric Imager instruments. We use several empirical models to understand the three-dimensional geometry and propagation of the CME, analyze the in-situ characteristics of the associated ICME, and investigate the characteristics of the MC by comparing four independent flux-rope model fits with the launch observations and magnetic-field orientations. The geometry and orientations of the CME from the heliospheric-density reconstructions and the in-situ modeling are remarkably consistent. Lastly, this event demonstrates that a careful analysis of all aspects of the development and evolution of a CME is necessary to correctly identify the solar counterpart of an ICME/MC.  相似文献   

11.
Pioneer VI was launched into a circumsolar orbit on December 16, 1965, and was occulted by the sun in the latter half of November, 1968. During the occultation period, the 2292-MHz S-band telemetry carrier underwent Faraday rotation due to the interaction of this signal with the plasma and magnetic field in the solar corona. The NASA/JPL 210-ft diameter antenna of the Deep Space Network near Barstow, California, was used for the measurement. The antenna feed was modified for automatic polarization tracking for this experiment. The measurement results are interpreted with a theoretical model of the solar corona. This model consists of a modified Allen-Baumbach electron density and a coronal magnetic field calculated both from Mount Wilson magnetograph observations using a source surface model and field extrapolations from the Explorer 33 satellite magnetometer. The observations and the calculated rotation show general agreement with respect to magnitude, sense, and timing, suggesting the source-surface model and field extrapolations from 1 AU are a valid technique to obtain the magnetic field in the corona from 4 to 12 solar radii. Variations present can easily be ascribed to density enhancements known to be present in the corona. Longitudinal variations of the density in the corona cannot be obtained from coronagraph observations, and thus a purely radial variation was assumed. An improved fit to the Faraday rotation data is obtained with an equatorial electron density $$N = 10^8 \left( {\frac{{6000}}{{R^{10} }} + \frac{{0.002}}{{R^2 }}} \right)...{\text{ cm}}^{{\text{ - 3}}} {\text{ (4 < }}R < 12){\text{ }}...$$ where R is in solar radii. The work of W. V. T. Rusch and J. E. Ohlson was supported in part by research sponsored by the Joint Services Electronics Program through the Air Force Office of Scientific Research under Grant AF-AFOSR 69-1622A at the University of Southern California. The work done by K. H. Schatten was in part supported by the National Academy of Science on a National Research Council postdoctoral fellowship. The work of J. M. Wilcox was supported in part by the Office of Naval Research under Contract Nonr 3656(26), by the National Aeronautics and Space Administration under Grant NGR 05-003-230, and by the National Science Foundation under Grant GA-1319 at the University of California at Berkeley.  相似文献   

12.
We have studied the dynamical properties of convective overstability and Kelvin-Helmholtz instability in a vertical magnetic field with a downdraft. The Kelvin-Helmholtz instability and overstability produce the upward downward propagating Alfvén waves depending upon the magnitudes of the kinematic viscosity coefficient (eddy viscosity) ν, and thermometric conductivity κ. It is found that the instability may be driven by the density stratification and the effect of the eddy viscosity is to make the system stable. We discuss also the interaction of the overstability inx<0 and the downdraft inx>0, and the overstability at a vertical boundary of the field.  相似文献   

13.
We present the results of spectroscopic and photometric observations for three hot southern-hemisphere post-AGB objects, Hen 3-1347 = IRAS 17074-1845, Hen 3-1428 = IRAS 17311-4924, and LSS 4634 = IRAS 18023-3409. In the spectrograms taken with the 1.9-m telescope of the South African Astronomical Observatory (SAAO) in 2012, we have measured the equivalent widths of the most prominent spectral lines. Comparison of the new data with those published previously points to a change in the spectra of Hen 3-1428 and LSS 4634 in the last 20 years. Based on ASAS data, we have detected rapid photometric variability in all three stars with an amplitude up to 0 · m 3-0 · m 4 in the V band. A similarity between the patterns of variability for the sample stars and other hot protoplanetary nebulae is pointed out. We present the results of UBV observations for Hen 3-1347, according to which the star undergoes rapid irregular brightness variations with maximum amplitudes ΔV = 0 · m 25, ΔB = 0 · m 25, and ΔU = 0 · m 30 and shows color-magnitude correlations. Based on archival data, we have traced the photometric history of the stars over more than 100 years. Hen 3-1347 and LSS 4634 have exhibited a significant fading on a long time scale. The revealed brightness and spectrum variations in the stars, along with evidence for their enhanced mass, may be indicative of their rapid post-AGB evolution.  相似文献   

14.
L. Mollwo 《Solar physics》1983,83(2):305-320
The earlier interpretation of the Zebra patterns by the concept of double resonance is examined for a realistic magneto-hydrostatic model of a coronal condensation over a bipolar spot group. It appears that the frequency drift of the Zebra stripes over a longer time can scarcely be explained by a change of state of the plasma as done till now. The proposed modified mechanism is based on a helical beam of electrons forming fronts that excite radiation at places of double resonance. Considering the field and density configuration conditions are found which produce drifting Zebra stripes. Structures of longer duration and absorptions arise from more or less overlapping stripe segments, which are excited by the fronts following one another in a beam of sufficient great length. The second stripe system of other drift direction found by Slottje (1972a) arises from lateral splitting of the beam.  相似文献   

15.
Photodesorption from dust grains by an anisotropic radiation field will lead to much greater momentum transfer than that associated with radiation pressure. This can cause the segregation of dust to the centres of moderately dense interstellar clouds.  相似文献   

16.
We describe briefly the Ultraviolet Spectrometer and Polarimeter on the Solar Maximum Mission and discuss data pertaining to the emissions observed in lines originating in the transition-region plasma, particularly during impulsive flares. The data pertain to lines from the following ions: SiII, CIV, OIV, SiIV, OV, and FeXXI.  相似文献   

17.
The paper describes a new sensor for the spatial registration and measurement of particle parameters in near and deep space. The following modern materials are applied in the sensor structure: a PVDF piezoactive film and lightweight heat-shielding high-temperature aerogel. The results from studying the aerogel morphology as well as its thermal conductivity depending on the air temperature are presented. The thermal conductivity of a SiO2-aerogel is compared with one of foreign aerogels and air. Its elemental quantitative chemical composition is determined.  相似文献   

18.
We analyse a simple one degree of freedom Hamiltonian system depending upon a parameter \(H = - 3(\delta + 1)R + R^2 - 2\sqrt {2R} \cos r\) . This model is much closer to resonance problems arising in Celestial Mechanics than the pendulum. We deduce from it the conditions of capture into resonance or escape from resonance for systems drifting slowly. We apply this analysis to the Enceladus-Dione resonance.  相似文献   

19.
Spectrograph and multiple-band polarimeter observations of the 24 April 1981 white-light flare indicate the presence of an optical continuum with intensity increasing strongly below 4000 Å. The flare emission (lines and continuum combined) is unpolarized and, at 3600 Å, exceeds the brightness of the background solar surface by 360%. Analysis of the spectrum between 3600 and 8200 Å, at a location three arc sec from the brightest point in the kernel, yields a probable temperature of 6700 K for the continuum emitting layer. The wavelength dependence of the continuum indicates emission by both negative hydrogen (H?) and Balmer continuum, with the H? probably originating in the upper photosphere at a height (above τ5000 Å = 1) in the range 200–300 km. Analysis of the Balmer lines and continuum yields an electron density 5.3 × 1013 cm?3 and a second-level hydrogen column density 1.1 × 1016 cm?2. The peak radiative output integrated over wavelength is 6.1 × 1027 erg s?1. The observed continuum intensity, if originating at a height of 300 km, implies an energy loss rate of 103 erg s?1 cm?3.  相似文献   

20.
The First Light Adaptive Optics (FLAO) system has been successfully commissioned at the Large Binocular Telescope. It delivers extreme adaptive optics performance using bright natural guide stars reaching 90 % Strehl Ratios in H-band. Observations with current adaptive optics systems are limited to the near infrared wavelengths, in these bands the diffraction limited resolution of the largest ground-based telescopes (8–10 meter class) is comparable to the one of the much smaller Hubble Space Telescope that observes in the visible bands. This study aims to demonstrate the feasibility of an adaptive optics system designed to achieve very high order correction at visible wavelengths (0.5 to 0.8 μ m) with significant sky coverage. Upgrading the FLAO design with a low noise CCD relaxes the reference magnitude limit needed to achieve greater performance. In particular, we demonstrate that a gain of 1–2 magnitudes is possible by upgrading the wavefront sensor with a very low read out noise CCD. For future AO systems, in addition to low noise CCDs, deformable (secondary) mirrors with a higher actuator density will be able to move the high order correction capability from the near infrared to the visible wavelengths (Strehl Ratio of 80 % in R (0.7 μ m), 60 % in V (0.5 μ m)). We investigate, by means of numerical simulation, the gain in imaging performance obtained at Near Infrared, Visible, and UV wavelengths. The results of these simulations have been used to derive the empirical relation between Strehl Ratio and magnitude of the reference star and we then use this relationship to perform a detailed sky coverage analysis based on astronomical catalog data. The detailed simulations of the Point Spread Functions allow us to compute Ensquared Energy and Strehl Ratio for the magnitude working range of such an Adaptive Optics system. We present the results of the instrumental isoplanatic angle determination. We then used these values to compute the relationship between correction level and the off-axis angle from the reference star. The Strehl Ratio relationship with the reference magnitude and the angular distance provides the information needed to perform the sky-coverage analysis, which demonstrates that the designed system is able to provide V and R bands correction on a not negligible few percent of the sky.  相似文献   

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