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1.
In this paper of the series, the literal analytical expressions for the Fourier expansion of the Earth's spherical harmonic potential will be explored in terms of the sectorial variables j (i) introduced in Paper IV (Sharaf, 1982) to regularize the highly-oscillating perturbation force of some orbital systems.Now at the Department of Astronomy, King Abdulaziz University Jeddah, Saudi Arabia.  相似文献   

2.
In this paper of the series, a special perturbation technique of Encke-type associated with the KS regularized variables will be developed for satellite motions in the Earth's gravitational field with axial symmetry. Its computational algorithm is of recursive nature and could be applied for any perturbed conic motion whatever the number of the zonal harmonic coefficients may be. Applications of the algorithm are also included.Now at the Department of Mathematics, Girls College of Education, Jeddah, Saudi Arabia.  相似文献   

3.
The crash of comet Shoemaker-Levy 9 fragments with Jupiter was observed at Aziziah Observatory, Hail, in Saudi Arabia. Three different observational methods (CCD photometric, spectroscopic, and photoelectric photometric) were used. The observations began on the 13th of July and ended on the 23 of July 1994. The CCD photometric results of the impact of fragmentsG andL are presented here, showing clearly the dark clouds resulted from those impacts. The measurements of the Titanium Oxide (TiO) absorption depth of impactsG andL showed an increase compared to the absorption depth of undisturbed regions, which indicates an increase in the TiO abundance. The increase in the colour reddening towards shorter wavelength found inG andL impacts indicate a composition of small size dust particles. Based on observations obtained at Aziziah Observatory, Saudi Arabia.  相似文献   

4.
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Shock features (right) identifi ed in the core (left) taken at a depth of 120 m from the Saqqar structure in Saudi Arabia prove the structure was formed by a hypervelocity impact event. Thomas Kenkmann et al. discuss the structure in their article on pp. 1925–1940. Images courtesy of T. Kenkmann.  相似文献   

5.
This report presents bulk composition data for 10 lunar meteorite stones from Oman for which the names have been approved since June, 2012. On the basis of composition and reported find location, four new meteorites are represented among this group of stones. Data from neutron activation analysis of 371 subsamples of all lunar meteorites from Oman and Saudi Arabia analyzed in this laboratory are presented.  相似文献   

6.
Astronomy is a very interesting subject for undergraduate students studying physics. In this paper, we report astronomy education for undergraduate students in the Physics Department of Guangzhou University, and how we are teaching astronomy to the students. Astrophysics has been rapidly developing since 1994, when the center for astrophysics was founded. Now, astrophysics has become a key subject in Guangdong Province, and the Astronomy Science and Technology Research Laboratory one of the key laboratories of the Department of Education of the Guangdong Province. Many undergraduate students, working under the tutorship of faculty members completed their thesis at the Center for Astrophysics in Guangzhou.  相似文献   

7.
The stratified core sample returned from Mare Crisium by the Luna 24 unmanned space probe is composed primarily of a new variety of subophitic to ophitic basalt with very low contents of TiO2 and MgO. This consists of clinopyroxene, calcic plagioclase, olivine, and minor amounts of silica, chromite, ulvöspinel, ilmenite, troilite, apatite, and Fe-metal. Granular metabasalts have the same bulk composition, but mineral phases exhibit less compositional variation. Fine-grained impact melts have similar compositions and are apparently derived from these basalts. We conclude that the basalts, which are chemically distinct from the very-low-titanium basalts found elsewhere on the Moon, represent the local surface flows of Mare Crisium.Sparse fragments of an olivine vitrophyre that is low in TiO2 but high in MgO and approaches the composition of the Apollo 15 green glasses may be derived from patches of dark mantling materials 20 km from the landing site.Now at Department of Geology, University of California at Davis, Davis, Calif., U.S.A.Now at Department of Geological Sciences, The University of Tennessee, Knoxville, Tenn., U.S.A.  相似文献   

8.
We report detailed observations of the herringbone (HB) fine structure on type II solar radio bursts. Data from the Culgoora radiospectrograph, radiometer and radioheliograph are analyzed. We determine the characteristic spectral profiles, frequency drift rates and exciter velocities, fluxes, source sizes, brightness temperatures, and polarizations of individual HB bursts. Correlations between individual bursts within the characteristic groups of bursts and the properties of the associated type II bursts are examined. Our data are compatible with HB bursts being radiation at multiples of the plasma frequency generated by electron streams accelerated by the type II shock. We conclude that HB bursts are physically distinct phenomena from type II and type III bursts, differing significantly in emission processes and/or source conditions; this conclusion indicates that many of the presently available theoretical ideas for HB bursts are incorrect.Now at: Department of Physics and Astronomy, University of Iowa, U.S.A.Now at Anglo-Australian Observatory, Sydney, Australia.  相似文献   

9.
By using solar spectrum intensity measurements, the aerosol optical depth and the atmospheric turbidity coefficients of Bahrain's atmosphere, i.e. the Linke turbidity factorT and Ångström coefficient, have been calculated at discrete wavelengths from 350 to 800 nm. A linear regression model was fitted forT versus for such a humid climate and it was compared to models reported for desert (Dhahran, Saudi Arabia) and temperate (Avignon, France) climates. A relationship between the linear regression slope,b, and the function of concentration and size distribution of particles,, over wide wavelength range was found.  相似文献   

10.
Solar disturbances modulate primary cosmic rays on different time scales. Studying cosmic ray variation is an important subject that attracts scientists from different disciplines. We have constructed and installed (in Riyadh, Saudi Arabia, Rc =14.4 GV) a three-layer small (20 × 20 cm2) MultiWire Chamber (MWC) telescope to study cosmic ray variations and investigate their influence on various atmospheric and environmental processes. Preliminary results obtained from the developed detector are given. The influence of both atmospheric pressure and temperature was studied. Both the temperature and pressure coefficients were calculated and were consistent with those previously obtained. Short-term cosmic ray periodicities, such as the 27-day period, and its two harmonics, have been identified. Sporadic variations caused by some solar activity processes have been inspected. The obtained results from this detector have been compared to the existing 1 m2 scintillator detector, as well as to some of the neutron monitors, showing comparable results.  相似文献   

11.
The large-scale photospheric magnetic field has been computed by allowing observed active region fields to diffuse and to be sheared by differential rotation in accordance with the Leighton (1969) magnetokinematic model of the solar cycle. The differential rotation of the computed field patterns as determined by autocorrelation curves is similar to that of the observed photospheric field, and poleward of 20° latitude both are significantly different from the differential rotation of the long-lived sunspots (Newton and Nunn, 1951) used as an input into the computations.Now at Department of Physics, Victoria University of Wellington, Wellington, New Zealand.  相似文献   

12.
We generalize previous studies of Alfvénic oscillations in the solar atmosphere to geometries in which the background magnetic field is not parallel to the gravitational acceleration. A uniform but inclined field produces only subtle changes in the mathematics, and virtually no changes to the coronal energy flux, over previous vertical field studies. We show that simple, two-layer models agree remarkably well with more sophisticated, multi-layer calculations. In addition, we derive several useful and accurate analytic results with which we highlight many features and parameter dependences. We also study a model with a spreading field geometry. For low magnetic fields (- 10 G) the corona still appears WKB to the oscillations and we do not find any significant deviations from the uniform field calculations. This is not the case for higher magnetic fields in active regions (- 3000 G) where we confirm previous results which suggest an order of magnitude increase in the coronal flux. Again, we derive useful analytic approximations.Now at: Mathematics Department, Monash University, Clayton, Victoria, Australia.  相似文献   

13.
A review of the available spectral geometric albedo measurements for Mars was presented earlier for the spectral region 0.3 to 1.1μ. A new observational study has greatly increased the store of data, especially for small Martian regions and for the infrared spectral region 1.0 to 2.5μ. Here we combine the new data with data both from the earlier review and, for the infrared spectral region, from the literature. We present a more complete picture of Martian spectral reflectivity properties than was available. This study should provide a more firm basis upon which models of Martian surface composition can be built. At visible wavelengths the Mars dark area Syrtis Major is red rather than green or grey in color; the bright area Arabia is even redder than Syrtis Major. Absorption bands, which differ between bright and dark areas, appear in the reflection curves. The 1μ absorption feature for dark areas is confirmed and more completely described. A previously unreported absorption band near 0.95μ for bright areas appears along with several absorption features in the infrared. The geometric albedo for Arabia reaches a maximum of about 0.43 at 1μ. The Bond albedo for this same area reaches a maximum of 60%. The bright area Arabia is occasionally three times brighter than the dark area Syrtis Major at red wavelengths. Published infrared reflection data available for Mars are not in complete agreement. Changes in brightness and color of Arabia are discussed which are not in agreement with traditional darkening wave theory.  相似文献   

14.
Abstract Al-Jimshan is a highly weathered 11.45 kg chondrite that was found in 1955 in the Rub' al Khali Desert, Saudi Arabia (20*42′N, 52*50E) about 240 km south-east of the town of al-Hadidah. The main mass is now at UCLA. Based on texture and mineral composition (olivine Fa17.7 ± 0.4; pyroxene Fs15.7 ± 1.0 Wo13 ± 0.4), al-Jimshan is classified as an H4 chondrite of shock stage S2. The Bir-Hadi and ad-Dahbubah H chondrites, which also were found in the Rub'al Khali (Holm, 1962), are probably not paired with al-Jimshan. They are classified as H5, shock stage S3 (Fa18.1 ± 0.5, n = 10; Fs16.0 ± 0.6, Wo1.1 ± 0.4, n = 9) and H5, shock stage S2 (Fa17.9 ± 0.3, n = 10; FS15.5 ± 0.2 Wo1.0 ± 0.4, n = 10), respectively.  相似文献   

15.
A discussion is given of slitless spectrograms of the chromosphere obtained by an expedition of the High Altitude Observatory, Sacramento Peak Observatory, and National Bureau of Standards at the eclipse of 4–5 February 1962. The data which are considered consist of previously published line intensities plus continuum data presented here for the first time.The data reduction procedure is briefly reviewed and a source of error introduced during the reduction is described. The error can possibly affect many of the reported line intensities.Comparison of the 1962 observations with the HAO data from the 1952 eclipse indicates that the previously suggested factor-of-two decrease in the earlier data should be modified to a wavelength-dependent correction: a decrease by a factor of three or four at the high Balmer lines, a decrease by a factor of two at 4700 A, no change at H, and an increase by a factor of about 1.5 at the Paschen lines. The observed Balmer-to-Paschen line intensity ratios are therefore in the theoretically acceptable range, in contrast to the 1952 results. The height gradients of the Balmer line intensities agree reasonably well although the 1962 data tend to curve downward relative to a simple exponential distribution.Based in part on a Ph.D. thesis submitted to the Department of Astro-Geophysics, University of Colorado.Now at the Department of Astronomy, Indiana University.  相似文献   

16.
Intrigued by the recent advances in research on solving Kepler's equation, we have attacked the problem too. Our contributions emphasize the unified derivation of all known bounds and several starting values, a proof of the optimality of these bounds, a very thorough numerical exploration of a large variety of starting values and solution techniques in both mean anomaly/eccentricity space and eccentric anomaly/eccentricity space, and finally the best and simplest starting value/solution algorithm: M + e and Wegstein's secant modification of the method of successive substitutions. The very close second is Broucke's bounds coupled with Newton's second-order scheme.This work was sponsored by the Department of the Air Force under Contract F19628-85-C-0002. The views are those of the authors and do not reflect the official policy or position of the U.S. Government.Now at Space Telescope Science Institute operated by AURA, Inc. for NASA.  相似文献   

17.
The dynamic spectral characteristics of the thermal model for solar hard X-ray bursts recently proposed by Brown et al. (1979) (BMS) are investigated. It is pointed out that this model, in which a single source is heated impulsively and cooled by anomalous conduction across an ion-acoustic turbulent thermal front, predicts that the total source emission measure should rise as the temperature falls. This prediction, which is common to all conductively cooled single-source models, is contrary to observations of many simple spike bursts. It is proposed, therefore, that the hard X-ray source may consist of a distribution of many small impulsively-heated kernels, each cooled by anomalous conduction, with lifetimes shorter than current burst data temporal resolution. In this case the dynamic spectra of bursts are governed by the dynamic evolution of the kernel production process, such as magnetic-field dissipation in the tearing mode. An integral equation is formulated, the solution of which yields information on this kernel production process, from dynamic burst spectra, for any kernel model.With a BMS-type kernel model in one-dimensional form, the derived instantaneous spectra are limited in hardness to spectral indices 4 for any kernel production process, due to the nature of the conductive cooling. Ion-acoustic conductive cooling in three dimensions, however, increases the limiting spectral hardness to 3. Other forms of anomalous conduction yield similar results but could permit bursts as hard as 2, consistent with the hardest observed.The contribution to the X-ray spectrum from the escaping tail of high-energy kernel electrons in the BMS model is calculated in various limits. If this tail dissipates purely collisionally, for example, its thick-target bremsstrahlung can significantly modify the kernel spectrum at the high-energy end. The energetics of this dynamic dissipation model for thermal hard X-ray bursts also are briefly discussed.Now at: Department of Mathematics, University of Waikato, Hamilton, New Zealand.  相似文献   

18.
The solar spectrum of wavelength 350–800 nm has been measured for the four seasons. The intensity of the solar radiation in W m-2 nm-1 has been calculated and used to estimate the monochromatic optical depth of Bahrain's sky. It was found that the optical depth (i.e., extinction coefficient,k) is least in winter and highest in summer. Comparison of the hourly variation of the optical depth between Bahrain's atmosphere and that of Dhahran (Saudi Arabia) shows that the abundance of small size particles in the former is more than in the latter. This causes more extinction effect in Bahrain than in Dhahran, especially in the wavelengths 350–525 nm. The relation betweenk and for each season in Bahrain is in the formk =A n , whereA is a constant andn is a negative integer, is reported in this study.  相似文献   

19.
It has been shown that the solar line 5250.2 (Fei) is weakly blended with a telluric line in the water vapor spectrum, and that magnetograms taken using this line are therefore inaccurate. We investigate the effects of this contamination on the Mount Wilson synoptic magnetograph data, which is based on 5250.2. Using spectrum scans taken at Kitt Peak, we model the contamination and develop a procedure that would correct for it, whenever the slant water vapor along the line of sight to the Sun is known. As this information is not available for the data collected thus far at Mount Wilson, we use the variation of determined quantities with airmass to obtain an average, or first-order, correction. Concentrating on the fitted coefficients for the solar rotation, the correction is found to be very slight, 0.5%, raising the value for the A coefficient, averaged over the period 3 December, 1985 to 22 July, 1990, from 2.8289 to 2.8422 rad s-1, The correction also removes a slight annual variation that has become discernible in the data collected since 1986.Now at Oregon Heath Sciences University, Portland, OR, U.S.A.Now at Department of Astronomy, University of Minnesota, U.S.A.  相似文献   

20.
A geologic analysis of 274 images acquired by the high-resolution MOC camera onboard the Mars Global Surveyor spacecraft within the Arabia Terra low neutron flux anomaly (which is indicative of an anomalously high abundance of hydrogen: up to 16 wt % of the equivalent amount of water) was performed. Correlation between the enhanced abundance of equivalent water with the presence of dust on the surface was found. Since dust plays a key role in condensation of water from the atmosphere, we suppose that the anomalies could result from the retention of atmospheric moisture. To analyze this suggestion, we performed a theoretical modeling that allowed us to map the planetary-scale distributions of several meteorological parameters responsible for the atmospheric moisture condensation. Two antipodal regions coinciding rather well with the Arabia Terra anomaly and the geographically antipodal anomaly southwest of Olympus Mons were found in the maps. This suggests that the anomalies are rather recent than ancient formations. They were probably formed by a sink of moisture from the atmosphere in the areas where present meteorological conditions support this sink. Geological parameters, primarily the presence of dust, only promote this process. We cannot exclude the possibility that the Martian cryosphere, rather than the atmosphere, supplied the studied anomalies with moisture during their formation: the thermodynamic conditions in the anomaly areas could block the moisture flux from the Martian interior in the upper regolith layer. The moisture coming from the atmosphere or from the interior is likely held as chemically bound water entering into the structure of water-bearing minerals (probably, hydrated magnesium sulfates) directly from the vapor; or the moisture precipitates as frost, penetrates into microfissures, and then is bound in minerals. Probably, another geologic factor—the magnesium sulfate abundance—works in the Arabia Terra anomaly.  相似文献   

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