共查询到20条相似文献，搜索用时 436 毫秒
1.
W. R. Dick S. Hirte E. Schilbach R. -D. Scholz 《Astrophysics and Space Science》1991,177(1-2):229-234
The observations and the plate reduction technique for the determination of positions and absolute proper motions which is used in Potsdam are described. Recent results have shown that an accuracy of about 0
.
1 for positions and 0
.
7
cent
.
–1
for proper motions can be achieved both for bright (8m–12m) and faint (16m–18m) stars. Three astrometric programmes using the Tautenburg plates are presented. 相似文献
2.
Richard C. Willson 《Solar physics》1981,74(1):217-229
Pyrheliometry, definition of the radiation scale in the International System of Units and monitoring the variability of solar total irradiance have been a focus of research at the Jet Propulsion Laboratory since the mid 1960's. A series of automated, electrically self-calibrating, cavity pyrheliometers known as Active Cavity Radiometers (ACR's) was developed as part of this program. A series of ground based experiments in 1968–69 led to the discovery of a systematic error in the International Pyrheliometric Scale. ACR's were among the instruments used to define the World Radiometric Reference in 1975.ACR flight experiments have been conducted to determine the 1 AU total solar irradiance and monitor its variability in time. A 1969 balloon experiment yielded a 1366 W m-2 result. The value from a 1976 sounding rocket experiment was 1368.1 W m-2. The results for two additional rocket experiments in 1978 and 80, revised in accordance with recent calibrations of ACR response to elevated pressures during these flights are: 1367.6 and 1367.8 W m-2, respectively. An ACR experiment (ACRIM) on the Solar Maximum Mission satellite has shown continuous variability of the total solar flux below the ±0.05% level and two large, temporary decreases of 0.1–0.2% lasting more than a week. The mean 1 AU total flux for ACRIM's first five months' observations was 1367.7 W m-2. Inflight comparison of ACR rocket and satellite measurements in May, 1980 demonstrated agreement to within ±0.05%. The 1 AU total solar irradiance results from ACR rocket and satellite experiments between 1976 and 1980 differ from their mean of 1367.8 W m-2 by no more than ±0.02%. The less precise 1969 balloon result is 0.1% lower. Although no observations were made from 1970–75, if solar behaviour in those five years was similar to that observed since 1976 then the upper limits of long term solar total irradiance variability are ±0.2% for the 1969–1980 period and ±0.1% between 1976 and 1980, based on the set of ACR observations.Proceedings of the 14th ESLAB Symposium on Physics of Solar Variations, 16–19 September 1980, Scheveningen, The Netherlands. 相似文献
3.
C. J. Cremers 《Earth, Moon, and Planets》1972,4(1-2):88-92
The thermal conductivity of an Apollo 12 fines sample (12001,19) was measured under vacuum conditions over a temperature range of 200 K to 400 K for a density of 1640 kg/m3. It was found to vary from approximately 1.2 × 10–3 W/m – K to about 2.6 × 10–3 W/m – K respectively. A least-squares curve fitted to the data according to the relationk =A +BT
3 was found to represent the data satisfactorily. 相似文献
4.
A series of telescopes having approximately a 30° half opening angle and responding to neutrons in the energy range 50 MeV to 350 MeV has been flown to the top of the atmosphere on balloons released from an equatorial launching site at Kampala, Uganda, between 1967 and 1969. The aim of the experiment was to attempt to detect solar neutrons during periods of enhanced solar activity. No neutrons of solar origin were detected, but an upper limit of the order of 30 neutrons m–2 s–1 at the Earth has been placed on the continuous solar neutron flux in the above energy range, and a limit of four photons m–2 s–1 has also been placed on the corresponding -ray flux above 80 MeV. Limits have likewise been placed on the total emission from various flares. For a 1B flare the values were 23 × 104 neutrons m–2 and 6 × 104 photons m–2. 相似文献
5.
V. V. Krymkin 《Astrophysics and Space Science》1978,58(2):347-352
Observations of the ionized hydrogen region NGC 1499 have been carried out with the radio telescope UTR-2 at frequencies 12.6, 14.7, 16.7, 20 and 25 MHz. The half-power resolution of the instrument to zenith is 28×34 at 25 MHz. The average volume density of the non-thermal radio emission between the Sun and the nebula (1.75×10–40 W m–3 Hz–1 ster–1 at 25 MHz), the electron temperature of the HII nebula (T
e
=4400 K), the measure of emission (ME=1500 cm–6 pc) and other parameters have been obtained. Maps of brightness distribution over the source are presented for each observation frequency. The results are compared with previously obtained data. 相似文献
6.
R. Viotti 《Astrophysics and Space Science》1969,5(3):323-332
The excitation temperature, colour excess and continuum of Car in the visible and near ultraviolet have been determined from the study of the excitation of the ionized iron emission lines. The excitation temperatures of Feii and [Feii] are about 8000K, value which is very much lower than the mean ionization temperature of the elements in Car.E
B-V
is about 1m.1; the absolute visual magnitude is presently –10m.5±1m. From the equivalent widths of the emission lines the true continuum between 1.5 and 3.0 –1 has been derived. The correspondingB-V is –0m.14, while the Balmer jump is less than 0m.5. The continuum appears mainly nebular in origin with a strong contribution of the two-photon emission from the 2s-level of hydrogen in the blue. 相似文献
7.
P. Hoyng 《Solar physics》1991,133(1):43-50
The resonant scattering spectrometers of the IRIS ground-based network for measuring whole-disc solar velocity oscillations make use of a piezoelastic modulator. The velocity noise generated by this optical component is analysed with particular emphasis on the required stability of the amplitude of oscillation, a. The product of the absolute stability ¦ a – a
m
¦/a
m
and the relative stability a
r.m.s./a
m may not be larger than 10 –4 to 10 –5 (depending on specific wishes), where a
m
is the optimum amplitude. The velocity noise due to photon statistics is slightly enhanced, but other instrumental sources of velocity noise remain unaffected. 相似文献
8.
Hans KR. Myrabø 《Astrophysics and Space Science》1979,60(2):367-374
UBV measurements of the light of the night sky in the auroral zone during three seasons are presented. The mean brightness of the night sky in theV band is found to be equal one 18m1 star (arc sec)–2, with considerable variations. The observed meanB-V andU-B indicies are +0
.
m
7 and –1
.
m
6, respectively.Light curves of variable stars during strong auroral activities are also shown. On the basis of measurements we briefly discuss the possibility of accurate stellar photometry in the auroral region. 相似文献
9.
Ann T. Mecherikunnel 《Solar physics》1998,177(1-2):11-23
Simultaneous solar total irradiance observations performed by absolute radiometers on board satellites during the quiet-Sun period between solar cycles 21 and 22 (1985–1987), are analyzed to determine the solar total irradiance at 1 AU for the solar minimum. During the quiet-Sun period the total solar irradiance, UV irradiance, and the various solar activity indices show very little fluctuation. However, the absolute value of the solar total irradiance derived from the observations differ within the accuracy of the radiometers used in the measurements. Therefore, the question often arises about a reference value of the solar total irradiance for use in climate models and for computation of geophysical, and atmospheric parameters. This research is conducted as a part of the Solar Electromagnetic Radiation Study for Solar Cycle 22 (SOLERS22). On the basis of the study we recommended a reference value of 1367.0 ± 0.04 W m-2 for the solar total irradiance at 1 AU for a truly quiet Sun. We also find that the total solar irradiance data for the quiet-Sun period reveals strong short-term irradiance variations. 相似文献
10.
Different types of oscillatory motions were detected in the late phases of eruption of a prominence. We found oscillations of the prominence axis and diameter with periods of 4.3 and 9.1 min, corresponding to the eigenmodes m = 4 and m = 8 with a damping factor 4.6 × 10–3 s–1. A period about 4.5 min was found for oscillations of the pitch angle of the helically twisted filaments. The m = 2 and m = 3 eigenmodes could be also identified and they led to the final relaxation of the prominence axis. The observations are compared with a model in which we consider forces acting in a curved, cylindrical magnetic tube anchored at both ends in the photosphere and carrying an electric current. The stability of the prominence is discussed. 相似文献
11.
M. Burša 《Earth, Moon, and Planets》1984,30(2):189-192
The discrepancy between the observed apparent acceleration of the Moon in longitude (1) and the actual lunar laser ranging data (3), (4) is of the order of ~ 9 × 10–23 rad s–2. It cannot be explained by the rms errors in (1) and (3), (4); processes connected with the internal Earth's dynamics and accelerating the Earth in its rotation might be responsible for the phenomenon, leading to the decreasing of the principal moment of the Earth's inertia ~ – 3.2 × 1029m2 kg cy–1. 相似文献
12.
E. S. Dmitrienko 《Astrophysics》1996,39(2):112-114
UBVRI observations of the eclipsing symbiotic star CI Cyg made during 1991–1995 are analyzed, the results of which indicate that the system is in the same quiescent state as during 1985–1990. Variations in the "extra-eclipse" color index U-B with an amplitude of about 0m.3–0m.4 and a characteristic time of about 9–10 yr have been detected for the first time. A more thorough analysis of all available data in the UBVRI bands of the spectrum will be required to investigate the existence of possible long-period variations in the other color indices and brightness of the system.Translated fromAstrofizika, Vol. 39, No. 2, pp. 211–216, April–June, 1996. 相似文献
13.
Milan Burša 《Earth, Moon, and Planets》1994,65(3):291-294
The supposition is, the tidal and rotational distortions should be fully responsible for the Pluto's and Charon's figure parameters. The mean polar and equatorial flattenings have been estimated about 10–3, the second sectorial Stokes parameters about 9 × 10–5, the differences between equatorial principal moments of inertia about 6 × 1030 kg m2 (Pluto) and 2 × 1029 kg m2 (Charon). 相似文献
14.
Richard R. Weber 《Solar physics》1978,59(2):377-385
Flux density spectra have been determined for ninety-one simple type III solar bursts observed by the Goddard Space Flight Center radio astronomy experiment on the IMP-6 spacecraft during 1971 and 1972. Spectral peaks were found to occur at frequencies ranging from 44 kHz up to 2500 kHz. Half of the bursts peaked between 250 kHz and 900 kHz, corresponding to emission at solar distances of about 0.3 to 0.1 AU. Maximum burst flux density sometimes exceeds 10–14 W m–2 Hz–1. The primary factor controlling the spectral peak frequency of these bursts appears to be variation in intrinsic power radiated by the source as the exciter moves outward from the Sun, rather than radio propagation effects between the source and IMP-6. Thus, a burst spectrum strongly reflects the evolution of the properties of the exciting electron beam, and according to current theory, beam deceleration could help account for the observations. 相似文献
15.
V. V. Krymkin 《Astrophysics and Space Science》1978,54(1):187-197
The results of observations of the Rosette emission nebula NGC 2237 with the radio telescope UTR-2 at frequencies 12.6, 14.7, 16.7, 20.0 and 25.0 MHz are given in the shape of contours of constant brightness temperature. The half-power beamwidth of the telescope to zenith at 25.0 MHz was 28×38. Density weighted mean values for the non-thermal radio emissivity between the Sun and the source (7.9×10–41 W m–3 Hz–1 ster–1 at 25.0 MHz) and the ratio of the intensity of emissivity generated before the area and the intensity of galactic radio emissivity appearing beyond the area equal to 1.3 have been obtained. The electron temperatureT
e=3600 K, the optical depth (about ten at 25 MHz), the measure of emission (ME=3500 cm–6 pc), the electron densityN
e=8 cm–3 and the nebular mass 16.6×10+3
M
have been determined. A comparison with other observation results has been made. 相似文献
16.
Measurements made with a balloon-borne counter telescope having an exposure factor of 774 m2 sr s are reported. The telescope was flown from Palestine, Tex., during the fall of 1971 for a total of 10 h under an average residual atmospheric depth of 4.4 g cm–2. The data analysis indicates that the integral flux ratios above 1.3 Gev n–1 and 23 GeV n–1 are consistent with energy independence.National Academy of Science-Senior Resident Research Associate 相似文献
17.
V. Stra&#x;krbov L.R. Izmest'yeva E.A. Maksimova S. Fietz J. Nedoma J. Borovec G.I. Kobanova E.V. Shchetinina E.V. Pislegina 《Global and Planetary Change》2005,46(1-4):57
Three years of regular weekly/biweekly monitoring of seasonal changes in temperature, transparency, chlorophyll a (CHL) and bacteria [erythrosine-stained microscopic counts and cultivable colony forming units (CFUs)] at the vertical profile in the South basin of Lake Baikal (51°54′195″N, 105°04′235″E, depth 800 m) were evaluated. In more detail, the structure and function of phytoplankton and the microbial loop in the euphotic layer at the same site were investigated during the late-winter–early-spring period under the ice. The depth of euphotic zone (up to 1% of surface irradiation) was 35 to 40 m. Primary production was measured three times a week with the 14C method in 2, 10, 20, 30 and 40 m. Maximum production was found in 10 m, with lower values towards the surface (light inhibition) and towards the lower layers. The total production in cells larger than 1 μm in the column (0–40 m) was 204–240 mg C d−1 m−2, 30–40% of it being in cells 1–3 μm (mostly picocyanobacteria), which represented roughly 9% of the total chlorophyll a (estimated from pigment analyses). A major part of phytoplankton biomass was formed by diatoms (Synedra acus Hust., Asterionella formosa Hass. and Stephanodiscus meyerii Genkal & Popovskaya). Total production (including extracellular, dissolved organic matter) was 235–387 mg C day−1 m−2, and the exudates were readily used by bacteria (particles 0.2–1 μm). This part amounted to 1–5% of cellular production in 2 to 20 m and 11–77% of cellular production in 20–40 m, i.e., in light-limited layers. From 0 to 30 m, chlorophyll a concentration was 0.8 to 1.3 μg l−1, wherefrom it decreased rapidly to 0.1 μg l−1 towards the depth of 40 m. Bacteria (DAPI-stained microscopic counts) reached 0.5–1.4×106 ml−1; their cell volumes measured via image analysis were small (average 0.05 μm−3), often not well countable when erythrosine stain was used. Bacterial biomasses were in the range of 6–21 μg C l−1. Numbers of colony forming units (CFUs) on nutrient fish-agar were c. 3–4 orders lower than DAPI counts. The amounts of heterotrophic protists were low, whereby flagellates reached 6 to 87 ml−1 and ciliates, 0.2–1.2 ml−1 (mostly Oligotrichida). Bacterial production was measured in the same depths as primary production using 3H-thymidine (Thy) and 14C-leucine (Leu) uptake. Consistently, bacterial abundances, biomasses, thymidine and leucine production were higher by 30–50% in layers 2, 10 and 20 m compared with that in the deeper 30 and 40 m, where cellular primary production was negligible. Leucine uptake in the deeper layers was even three times lower than in the upper ones. From the comparison of primary and bacterial production, bacteria roughly use 20–40% of primary production during 24 h in the layers 2 to 20 m. 相似文献
18.
A detailed compilation of the most recent values of the solar constant is given (13 values published from 1967 to 1970). The most probable value seems to be 1.95 cal cm–2 min–1 or 1.36 kW m–2 with a formal rms error of ± 0.3%. The corresponding effective temperature is 5770K.Systematic errors of the order of ± 1%, but also a possible variability of the same order cannot be excluded. 相似文献
19.
Linear correlations between the diameter log of ring-shaped nebulae and the total number logN of embedded stars for two absolute magnitude levels of –2m and +2m for the LMC have been found. This shows that less luminous stars are also contributing towards the illumination of the nebulae. A method for the determination of relative ages of these loop nebulae is described.Based on observations collected at the Boyden Observatory, Bloemfontein, South Africa and the European Southern Observatory, La Silla, Chile. 相似文献
20.
Measurements of electron concentrations in the ionosphere, between 100 and 250 km altitude, were used to compute the increase in solar ionizing radiation during two flares on 21 and 23 May 1967. Since the altitude of maximum absorption of the solar energy (approximately unit optical depth) depends on the wavelength of the radiation, it is possible to estimate separately the energy enhancement in different portions of the spectrum. An ionizing energy flux increase of nearly 5 erg cm–2 sec–1 was observed on 21 May, while on the 23rd, the increase was over 7 erg cm–2 sec–1. In both flares, most of the absolute increase occurred in the 20–205 Å region of the spectrum, although the relative increase was much larger at the shorter wavelengths. 相似文献