Radiative Loss Rates Research Articles

Ionization equilibrium and radiative energy loss rates for C, N, and O ions in low-density plasmas

The results of calculations of the ionization equilibrium and radiative energy loss rates for C, N and O ions in low-density plasmas are presented for electron temperatures in the range 10 4–10 7 °K (∼1–10 3 eV). The ionization structure is determined using the steady-state corona model, in which electron impact ionization from the ground states is balanced by direct radiative and dielectronic recombination. Using an improved theory, detailed calculations are carried out for the dielectronic recombination rates in which account is taken of all radiative and autoionization processes involving a single-electron electricdipole transition of the recombining ion. The radiative energy loss processes considered are electron-impact excitation of resonance line emission, direct radiative recombination, dielectronic recombination, and electron-ion bremsstrahlung. For all three elements, resonance line emission resulting from 2 s−2 p transitions produces a broad maximum in the energy loss rate near 10 5°K(∼ 10 eV).

H? profiles from electron-heated solar flares

We briefly review the status of models of optical flare heating by electron bombardment. We recompute Brown's (1973a) flare model atmospheres using considerably revised radiative loss rates, based on Canfield's (1974b) method applied to α, Lα, and H−. Profiles of α are computed and compared with observation. The computed profiles agree satisfactorily with those observed during the large 1972 August 7 flare, if spatial and velocity inhomogeneities are assumed. The electron injection rate inferred from α is one order of magnitude less than that inferred from hard X-rays, for this event. This may be due to either (1) the neglect of a mechanism that reduces the thick-target electron injection rate or (2) failure to incorporate important radiative loss terms.

The influence of autoionization accompanied by excitation on dielectronic recombination and ionization equilibrium

In the process of dielectronic recombination, the doubly excited state formed by radiationless capture may autoionize preferentially into an excited state of the recombining ion. This additional autoionization process has not been discussed in previous treatments of dielectronic recombination. The dielectronic recombination rates for certain nonhydrogenic Fe ions, although still larger than the direct radiative recombination rates, are found to be substantially reduced by the inclusion of the additional autoionization rate in the branching ratio for the stabilizing radiative transition. Consequently, the temperatures of maximum equilibrium abundance are significantly lower than those predicted by recent calculations. Finally, the radiative energy loss rate coefficients are calculated for radiation processes involving electron Fe-ion collisions in high-temperature plasmas. Electron impact excitation of resonance line radiation is the dominant radiative cooling mechanism in steady-state plasmas at temperatures where ions with bound electrons are abundant. However, it is found that the radiation emitted during dielectronic recombination can be more important than direct recombination radiation and bremsstrahlung.

The Radiative Energy Loss from the Shock Front

The radiation loss from shock waves which are generated during the collapse of protostars ·has a great effect on the structure of protostars. In this paper, the effects of the continuum and line radiations on the shock structure are investigated and the radiation loss rates are calculated. Plane steady shocks are assumed and the ambient conditions are taken as v=60~20 km/sec and p=l0-8~10-13 g/cms. The atmospheres are assumed to consist of pure hydrogen atoms which have only three levels, i.e., the ground, excited and ionized levels. The computed results show that about 90 percent of the shock's initial kinetic energy es­ capes· ahead of the shock front as the Balmer continuum radiation. However, in the case of low .shock velocity (v;:S;30km/sec) or h1gh ambient density (p:G10-8g/cm 3), the fraction of the lost energy decreases below about 80 percent.

The critical condition for electrothermal instabilities

The critical Hall parameter β, wave vector K and propagation speed v have been derived by the use of dispersion equations, which contain terms connected with the total and local radiative loss rates and finite ionization — recombination rate α.

510. 試料のすべての面から輻射熱損失を伴う場合の温度伝導率の非定常測定法,(II)

This report discusses from theory a method of measuring the thermal diffusivity of a relatively thick disk-shaped specimen heated on the front face by periodic radiation. Thermal radiation losses from the lateral face as well as from the front and the rear faces are considered.The results are as follows: If 2r0/l_??_10.0 (2r0: diameter, l: thickness), the thermal diffusivity can be determined with the disk regarded as an infinite slab having no radiation loss from the lateral face. If 2r0/l_??_8.0, radiation loss from all faces of the disk should be taken into account in determining thermal diffusivity, by adopting the proposed method. Further, if 2r0/l_??_2.0 and at the same time the rate of thermal radiation loss is large, it should become difficult to measure thermal diffusivity with high accuracy, even by the present treatment.Experimental data obtained in the past based on Cowan's periodic method require re-examination in the light of the present finding since the shape of the specimens have ranged from 2r0/l=4.0 to 7.0.

Radiation flux from a slab or sphere

Green formula and moment functions, predicting rate of radiative energy loss from boundaries of absorbing-emitting slab or sphere

Hornbeck—Molnar Cross Sections for the n=3 States of Helium

Analysis of the atomic light originating from energy levels of principal quantum number n=3 in the helium positive column shows that a pressure-dependent loss process exists for states other than the S states. The loss mechanism is identified as the Hornbeck—Molnar process, He*+He→He2++e−,by observing the effects of varying the atomic populations when the positive column is irradiated with intense atomic light. Comparison of the pressure-dependent loss rate with the radiation loss rate from a particular state yields the Hornbeck—Molnar cross section. An independent measurement relating the molecular-ion concentration to the 33D population yields a separate value for the 33D cross section, which agrees quite well with that measured by the previous method.

Evolution with Neutrino Loss of a Massive Star until the Onset of Carbon Burning.

view Abstract Citations (6) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Evolution with Neutrino Loss of a Massive Star until the Onset of Carbon Burning. Hayashi, Chushiro ; Cameron, Robert C. Abstract Previously the authors pointed out [Astron. J. 67, 577,1962; see also, Hayashi, C., Hoshi, R., and Sugimoto, D. Progr. Theoret. Phys. Suppl. (Kyoto), No. 22, 1, 1962J that, assuming energy loss due to the universal Fermi interaction between electrons and neutrinos, the lifetime of a star of 15.6 solar masses as a red supergiant (post-helium-exhaustion phases) will be too short to account for the observed number of such stars in the cluster h and x Persei. The neutrino loss effect after the formation of a carbon- oxygen core has now been studied in detail by constructing a contracting-core model sequence. The hydrogen-rich envelope and a helium zone are neglected and the core is treated as a single star of 2.6 solar masses. As the contraction proceeds, a central isothermal core appears; its mass grows because of the rather high temperature dependence of the neutrino-loss rate. In the outer zone of lower temperature, the energy release (radiation loss) is due mainly to gravitational contraction. with the rate proportional to the temperature. Partial degeneracy and relativistic effects are included in the isothermal core computations. Fitting of the core and outer zone (accomplished by equating neutrino and radiation loss rates) shows that electron degeneracy sets in at the center when the mass of the core becomes about one-half solar mass; subsequently, the degenerate region grows somewhat rapidly with increasing temperature and density. When the core mass becomes about one solar mass, both the central density and temperature become high enough for the carbon flash to occur. The outer boundary of the isothermal core is always nondegenerate. Thus, neither the Scho~nberg-Chandrasekhar limit for a nondegenerate isothermal core, nor the Chandrasekhar limit for a degenerate configuration gives the critical stage for the contracting carbon-oxygen core. The lifetime of the contraction phase up to the onset of the carbon flash is not much different from our previous estimate, since it is determined essentially by the rate of gravitational contraction in the nondegenerate region. Publication: The Astronomical Journal Pub Date: 1964 DOI: 10.1086/109424 Bibcode: 1964AJ.....69R.140H full text sources ADS |

Energy Loss from a Toroidal Pinch Discharge

Most high-temperature plasma devices, and in particular pinch discharges, have energy-loss rates much larger than can be accounted for in terms of hydrogenic bremsstrahlung or quiescent plasma diffusion. This loss has been investigated for a toroidal pinch discharge machine with longitudinal stabilizing magnetic field, Perhapsatron S-4. It is found that the major energy dissipation is due to vacuum ultraviolet emission from partially stripped impurity ions. The impurity is predominantly oxygen liberated from the walls of the tube into the discharge after the pinch has been formed. Characteristics of this radiation are discussed, as well as a possible mechanism for the release of the impurity into the discharge. Comparisons between experimental results and theoretical predictions on the rate of radiation loss are given.