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51.
Alfred Kepiński 《Aquatic Sciences - Research Across Boundaries》1962,24(2):272-290
Ohne Zusammenfassung 相似文献
52.
Sh. B. Akhmedov G. B. Gelfreikh F. Fürstenberg J. Hildebrandt A. Krüger 《Solar physics》1983,88(1-2):103-108
Model calculations of the S-component are compared with observations of the RATAN-600 telescope at five discrete microwave frequencies referring to active region McMath No. 15974 on May 1, 1979. The spectral variations of source diameter, flux density, and degree of polarization are used to derive the height scale of the magnetic field in accordance with a magnetic dipole distribution under the assumption of advanced temperature and electron density distributions according to most recent EUV observations. 相似文献
53.
Two classes of volcanic plumes on Io 总被引:1,自引:0,他引:1
Comparison of Voyager 1 and Voyager 2 images of the south polar region of Io has revealed that a major volcanic eruption occured there during the period between the two spacecraft encounters. An annular deposit ~1400 km in diameter formed around the Aten Patera caldera (311°W, 48°S), the floor of which changed from orange to red-black. The characteristics of this eruption are remarkably similar to those described earlier for an eruption centered on Surt caldera (338°W, 45°N) that occured during the same period, also at high latitude, but in the north. Both volcanic centers were evidently inactive during the Voyager 1 and 2 encounters but were active sometime between the two. The geometric and colorimetric characteristics, as well as scale of the two annular deposits, are virtually identical; both resemble the surface features formed by the eruption of Pele (255°W, 18°S). These three very large plume eruptions suggest a class of eruption distinct from that of six smaller plumes observed to be continously active by both Voyagers 1 and 2. The smaller plumes, of which Prometheus is the type example, are longer-lived, deposit bright, whitish material, erupt at velocities of ~0.5 km sec?1, and are concentrated at low latitudes in an equatorial belt around the satellite. The very large Pele-type plumes, on the other hand, are relatively short-lived, deposit darker red materials, erupt at ~1.0 km sec?1, and (rather than restricted to a latitudinal band) are restricted in longitude from 240° to 360°W. Both direct thermal infrared temperature measurements and the implied color temperatures for quenched liquid sulfur suggest that hot spot temperatures of ~650°K are associated with the large plumes and temperatures <400°K with the small plumes. The typical eruption duration of the small plumes is at least several years; that of the large plumes appears to be of the order of days to weeks. The two classes therefore differ by more than two orders of magnitude in duration of eruption. Based on uv, visible, and infrared spectra, the small plumes seem to contain and deposit SO2 in their annuli whereas the large plumes apparently do not. Two other plumes that occur at either end of the linear feature Loki may be intermediate or hybrid between the two classes, exhibiting attributes of both. Additionally, Loki occurs in the area of overlap in the regional distributions of the two plume classes. Two distinct volcanic systems involving different volatiles may be responsible for the two classes. We propose that the discrete temperatures associated with the two classes are a direct reflection of sulfur's peculiar variation in viscosity with temperature. Over two temperature ranges (~400 to 430°K and >650°K), sulfur is a low-viscosity fluid (orange and black, respectively); at other temperatures it is either solid or has a high viscosity. As a result, there will be two zones in Io's crust in which liquid sulfur will flow freely: a shallow zone of orange sulfur and a deeper zone of black sulfur. A low-temperature system driven by SO2 heated to 400 to 400°K by the orange sulfur zone seems the best model for the small plumes; a system driven by sulfur heated to >650°K by hot or even molten silicates in the black sulfur zone seems the best explanation for the large plume class. The large Pele-type plumes are apparently concentrated in a region of the satellite in which a thinner sulfur-rich crust overlies the tidally heated silicate lithosphere, so the black sulfur zone may be fairly shallow in this region. The Prometheus-type plumes are possibly confined to the equatorial belt by some process that concentrates SO2 fluid in the equatorial crust. 相似文献
54.
Polarization measurements of type III bursts at 23.5 and 29.5 MHz have been compared for several years with indicators of magnetic fields in different height levels such as sunspot data, S-component characteristics, and noise storm data. By applying the Mount-Wilson and Brunner types of the related spot groups there results a positive relationship between the average degree of type III burst polarization and the magnitude or complexity of photospheric magnetic fields. For other parameters (leading spot area, peak intensity of the S-component at 9.1 cm wavelength) such a clear monotonic relation has not been found. Possibly the degree of polarization is influenced by height variations of the emitting level of the type III bursts at a fixed frequency due to variable electron densities. No connection has been detected between the type III burst polarization and noise storm fluxes which may be due to the local distance of the origin of both emissions. 相似文献
55.
Alfred Clark Jr. 《Solar physics》1968,4(4):386-400
Some theoretical models are given which illustrate the structure of chromospheric magnetic fields associated with supergranulation. It is found that the chromospheric fields depend critically on whether or not there are large-scale vertical motions at the level where the horizontal supergranule motions are observed. In the absence of such motions, the concentration of field produced in the photosphere does not persist more than a few scale heights into the chromosphere; however, the chromospheric mass density is increased above the supergranule boundaries in this case. Completely different results-such as a chromospheric potential field-may be obtained by the inclusion of vertical motions. It is concluded that a rather wide range of chromospheric-field structures is consistent with present observational knowledge of the supergranulation. 相似文献
56.
Martin?SchmidEmail author Andreas?Lorke Alfred?Wüest Michel?Halbwachs Gregory?Tanyileke 《Ocean Dynamics》2003,53(3):288-301
To prevent the recurrence of a disastrous eruption of carbon dioxide (CO2) from Lake Nyos, a degassing plan has been set up for the lake. Since there are concerns that the degassing of the lake may reduce the stability of the density stratification, there is an urgent need for a simulation tool to predict the evolution of the lake stratification in different scenarios. This paper describes the development of a numerical model to predict the CO2 and dissolved solids concentrations, and the temperature structure as well as the stability of the water column of Lake Nyos. The model is tested with profiles of CO2 concentrations and temperature taken in the years 1986 to 1996. It reproduces well the general mixing patterns observed in the lake. However, the intensity of the mixing tends to be overestimated in the epilimnion and underestimated in the monimolimnion. The overestimation of the mixing depth in the epilimnion is caused either by the parameterization of the k-epsilon model, or by the uncertainty in the calculation of the surface heat fluxes. The simulated mixing depth is highly sensitive to the surface heat fluxes, and errors in the mixing depth propagate from one year to the following. A precise simulation of the mixolimnion deepening therefore requires high accuracy in the meteorological forcing and the parameterization of the heat fluxes. Neither the meteorological data nor the formulae for the calculation of the heat fluxes are available with the necessary precision. Consequently, it will be indispensable to consider different forcing scenarios in the safety analysis in order to obtain robust boundary conditions for safe degassing. The input of temperature and CO2 to the lake bottom can be adequately simulated for the years 1986 to 1996 with a constant sublacustrine source of 18 l s–1 with a CO2 concentration of 0.395 mol l–1 and a temperature of 26 °C. The results of this study indicate that the model needs to be calibrated with more detailed field data before using it for its final purpose: the prediction of the stability and the safety of Lake Nyos during the degassing process.Responsible Editor: Hans Burchard 相似文献
57.
J. Hildebrandt A. Krüger I.M. Chertok V.V. Fomichev R.V. Gorgutsa 《Solar physics》1998,181(2):337-349
Usually the gyrosynchrotron emission of microwave bursts from electron populations with a power-law (PL) energy distribution has been considered under the assumption that the spectral index of the distribution is constant over a wide range of energies. Meanwhile, there is strong evidence, in particular from hard X-ray and -ray, but also from cm/mm wavelength radio observations, that in many solar flare events the spectrum of the emitting electrons is characterized by a significant hardening at energies above 100–500 keV. We present some examples of calculated microwave burst spectra at cm/mm wavelengths taking into account the above evidence. It is shown that a break in the energy spectrum of the PL electrons can indeed result in a spectral hardening sometimes observed in microwave bursts at frequencies above 10–30 GHz. 相似文献
58.
Aspects of GLONASS Carrier-Phase Differencing 总被引:2,自引:0,他引:2
59.
60.
Niranjan D. Chatterjee Ralf Krüger Gerd Haller Walter Olbricht 《Contributions to Mineralogy and Petrology》1998,133(1-2):149-168
An internally consistent thermodynamic dataset has been derived for 148 endmember phases (145 solids and 3 fluids) comprising
the elements Li, Na, K, Be, Mg, Ca, Ti, Cr, Mn, Fe, Zn, Al, Si, C, H, and O. This has been achieved by simultaneous treatment
of phase property (like standard enthalpy of formation, standard entropy, molar heat capacity, molar volume, thermal expansivity,
bulk modulus etc.) and reaction reversal data by the Bayesian method. The theory underlying the approach, and the computational
methods involved, are briefly outlined. (For the benefit of readers unfamiliar with inference statistics, the basic concepts
of the Bayes method are also presented in such a way that they can be grasped intuitively.) Although not yet addressed, this
method can be extended to refine the thermodynamic mixing properties of crystalline solutions. The sources of the input data,
culled from the literature, are summarized in the Appendix. The resulting database is succinctly documented in this paper.
It includes the enthalpies of formation and entropies, their uncertainties, and the correlation among them. The database allows
calculation of P-T, T-X
CO2, P-X
CO2, and T-f
O2 sections, with error propagation into the computed phase diagrams on a routine basis. A user-friendly computer program has
been written to generate such phase diagrams. It is public domain software. The software and the thermodynamic database (which
includes a complete documentation of the thermodynamic data above and beyond those listed (Table 2, here) may be downloaded from the web site
http://homepage.ruhr-uni-bochum.de/niranjan.chatterjee/Index.htm. Examples of computed phase diagrams are given to illustrate
the quality of the data and the capabilities of the software.
Received: 11 March 1998 / Accepted: 11 June 1998 相似文献