| The one-dimensional model is built to investigate the reaction-diffusion processes of air plasma by using numerical simulation. Two aspects are studied: one is the processes of air plasma in the discharges in open environment; another is the spatio-temporal decay of air plasma after discharge. The results are of great importance to the experimental and industry applications of air plasma.One-dimensional model of air plasma is described, and the numerical analysis is performed in cylindrical model. 34 kinds of particles and 146 reactions are considered in the model. Considering the stiffness of the system, the model is simulated by using QSSA (Quasi-steady-state approximation) method combined with rhombic finite difference schemeFirstly, the model of air plasma with a plasma source is built in Cartesian coordinates in order to investigate the low target feature plasma technology. The air plasma in the discharge is simulated in 60km. The results of numerical simulation are connected with an approximation analytical formula to estimate the necessary plasma flow for electron density when a stable state is formed. The result show that a stable state will form in a fixed space point by the act of plasma source. In order to get the plasma whose density is 1012cm-3 and thickness is about 1cm the plasma flow should to be 1018cm-2s-1.The model of the decay of air plasma after the discharge is built in both cylindrical coordinates and spherical coordinates. The spatial and temporal processes of air plasma in different pressure (1atm, 0.7atm, 0.5atm, 0.3atm and 0.1atm) are investigated. And the equivalent lifetimes of single filaments are obtained in experiment. The result show that the lower the pressure, the faster the diffusion and the slower the decay. Contrasting the numerical result with the experimental result, we found that the lower the pressure, the higher the equivalent lifetime of plasma, within the limit of 0.3atm~1atm.
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