Auroral NO chemistry is studied to determine the limits on [NO] and its production rate in steady auroral arcs. We conclude conservatively that the NO concentration cannot exceed 0.1[O2]. The precise value of this upper limit depends very sensitively on the relative yields of N(²D) and N(4S) in the reactions that are the major auroral sources of N atoms, and on the basis of the requirements of mid‐latitude models for odd nitrogen, a value of 0.03[O2] is estimated. Plausible auroral [NO] enhancements are of the order of (3–6) × 108 cm−3 after 10³ s and (1–4) × 109 cm−3 after 104 for a steady IBC 2+ arc.
Articles you may be interested inNumerical analysis of a mixture of Ar/NH3 microwave plasma chemical vapor deposition reactor Simulations of chemical vapor deposition diamond film growth using a kinetic Monte Carlo model and twodimensional models of microwave plasma and hot filament chemical vapor deposition reactors Probing the plasma chemistry in a microwave reactor used for diamond chemical vapor deposition by cavity ring down spectroscopy J. Appl. Phys.As a first step to carrying out two-dimensional simulations of microwave reactors we have performed very detailed one-point calculations using a Boltzmann code to determine the distribution of electron energy, detailed time dependent ion chemistry, and detailed neutral time dependent hydrocarhon chemistry. Modeling a microwave chemical vapor deposition reactor requires accurate determination of the electron energy distribution generated by the microwave electromagnetic fields and thcir interaction with the neutral gas because the distribution is highly nonthermal and the important dissociation and ionization rates are determined by the small fraction of high energy electrons. The electrons lose most of their energy to vibrational cxcitation of the gas which heats it through vibrational-translational energy exchange. The one-point model takes account in an approximate way of the effects of mass diffusion and thermal conduction to the reactor substrate and walls. We show time dependent calculations of the rise in gas temperature, the evolution of ion species, and the neutral species development in the pressure range of 40-110 Torr characteristic of conditions in an ASTeX reactor. We vary the input power and the input methane and oxygen fractions and compare with experimental measurements in the reactor.
A minimum variance iterative technique for the determination of ionospheric parameters, including electron and ion temperatures and densities, is presented. The method formally incorporates a priori information regarding the values of these parameters and, in particular, whatever information the experimenter has concerning the uncertainty associated with these values. With proper use of this additional information, convergence will be more rapid and more likely than would be the case were a priori information not employed. With certain mathematical models, singularities that occur in other techniques are avoided. In addition, procedures for generating nominal parameter estimates from the data have been devised. These techniques have been developed for, and lend themselves to, the automatic processing of large quantities of data. An example of the analysis of both ion and electron data is included for illustrative purposes.
A numerical hydrodynamics chemistry model to simulate the laser–target interaction experiment at the Naval Research Laboratory’s PHAROS [Laser Interaction and Related Plasma Phenomena (Plenum, New York, 1986), Vol. 7, p. 857] is presented. Both laser–target and debris–background interactions are modeled, solving mass continuity, total momentum, and separate ion and electron internal energy equations. The model is appropriate for background densities≥1 Torr. To accurately treat both the early-time planar ablation and the later spherical expansion of the blast wave, as well as the rear-side shock front, an oblate spheroidal coordinate system was adopted. The aluminum target ablates into and interacts with an ambient nitrogen gas, filling the facility chamber. The simulation models the target continuously from the solid state to the state of a highly ionized nonequilibrium plasma, including all charge states of aluminum and all charge states of the nitrogen background. The laser beam has a wavelength of 1 μ, a ∼5 nsec full width at half-maximum (FWHM), an intensity at the target surface ∼1013 W/cm2, and total energy varying from 20–100 J. The model accurately reproduces the measured time-of-flight profile and the mass of ablated aluminum. Expansion of the blast wave in the model follows the ideal Sedov relation until radiation losses force a deviation due to a failure in the constant energy assumption. In the shock wave region the simulations show electron density of a few times 1018 cm−3, temperatures ranging from 10–20 eV, and dominant nitrogen species of N+3 and N+4, all in agreement with experimental measurement. A calculated profile of electron density both in the shock and in the cavity region agree closely with experiment and imply an average aluminum charge state of 11 times ionized in the cavity out to late times, as predicted by the simulation described in this paper. The simulation suggests, also, that observed rear-side structuring is a result of a deceleration Rayleigh–Taylor instability. The model is capable of providing detailed predictions, which are presented, as to profiles of charge states, densities, and temperatures as a function of time; these predictions are not yet tested by experimental measurement.
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