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We discuss the difficulties encountered when the Heisenberg-Kolmogoroff model for turbulence is applied to the large-scale turbulence in: (A) molecular clouds (specifically the velocity vs size relationship) and (B) stars (specifically, the estimate of convective fluxes).A new model for large-scale turbulence is, therefore, needed. 相似文献
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The precise amount of O2 and O3 in the Earth's prebiological paleoatmosphere has been a topic of considerable discussion in the past. Since the photolysis of H2O and CO2, the prebiological mechanisms to produce O2, depends on the ultraviolet (UV) flux from the Sun, a reliable quantification of the problem requires detailed knowledge of such flux. Using the most recent astronomical observation of young stars from the International Ultraviolet Explorer, as well as a detailed photochemical model of the paleoatmosphere, we find that the amount of O2 in the prebiological paleoatmosphere may have been as much as 106 times greater than previously estimated.Some of the implications of this new value are discussed. 相似文献
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V. M. Canuto 《Earth, Moon, and Planets》1995,70(1-3):75-78
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V. Canuto C. Chiuderi C. K. Chou L. Fassio-Canuto 《Astrophysics and Space Science》1974,28(1):145-161
We present the energy losses due to several neutrinos processes: (1) synchrotron neutrinos, (2) pair annihilation neutrinos, (3) plasmon neutrinos, and (4) photoneutrinos in the presence of a superstrong magnetic field. Numerical results are tabulated and illustrated for several values of densities and temperatures. In the low density regime (107 g cm–3) the presence of a magnetic field decreases the luminosity, whereas the opposite is true at higher densities. This last effect is however almost entirely due to the existence of a new process the synchrotron neutrinos that disappear whenH0. Even though the overall effect can only be quantitatively ascertain after a complete cooling computation is performed, one should however expect a much lower temperature for neutron star surface than the one computed in theH=0 case. 相似文献
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The decay of a longitudinal plasmon into two neutrinos is studied in the presence of a strong magnetic field. Contrary to the transverse case, for longitudinal plasmons the existence of a new mode, entirely dependent on the magnetic field, greatly enhances the energy loss at high densities. Denoting byQ
HandQ
0the neutrino energy losses with and without magnetic field respectively, the situation is as follows: atH1011 G andT109K,Q
0105
Q
Hfor <1011g cm–3, WhileQ
H1010
Q
0for >1011g cm–3. A second physically interesting feature is the anisotropic character of the energy loss which is highly peaked along the field lines, giving rise to a shorter cooling time in that direction than in any other. 相似文献
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A quantum mechanical treatment of an electron plasma in a constant and homogeneous magnetic field is considered, with the aim of (a) defining the range of validity of the magnetoionic theory (b) studying the deviations from this theory, in applications involving high densities, and intense magnetic field. While treating the magnetic field exactly, a perturbation approach in the photon field is used to derive general expressions for the dielectric tensor . The properties of are explored in the various limits. Numerical estimates on the range of applicability of the magnetoionic theory are given for the case of the one-dimensional electron gas, where only the lowest Landau level is occupied. 相似文献
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Hsing-Hen Chen Malvin A. Ruderman Vittoria Canuto 《Astrophysics and Space Science》1974,31(1):187-191
We show, contrary to previously published results, that magnetic fields of astrophysical interest have negligible effects on the emission rate of neutrinos from plasmons. 相似文献