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In this paper,an improved air discharge fluid model under non-uniform electric field is constructed based on the plasma module COMSOL Multiphysics with artificial stability term,and the boundary conditions developed in the previous paper are applied to the calculation of photoionization rate.Based on the modified model,the characteristics of low temperature sub-atmospheric air discharge under 13 kV direct current voltage are discussed,including needle-plate and needle-needle electrode structures.Firstly,in order to verify the reliability of the model,a numerical example and an experimental verification were carried out for the modified model respectively.Both verification results show that the model can ensure the accuracy and repeatability of the calculation.Secondly,according to the calculation results of the modified model,under the same voltage and spacing,the reduced electric field under low temperature sub-atmosphere pressure is larger than that under normal temperature and atmospheric pressure.The high electric field leads to the air discharge at low temperature and sub atmospheric pressure entering the streamer initiation stage earlier,and has a faster propagation speed in the streamer development stage,which shortens the overall discharge time.Finally,the discharge characteristics of the two electrode structures are compared,and it is found that the biggest difference between them is that there is a pre-ionization region near the cathode in the needle-needle electrode structure.When the pre-ionization level reaches 1013 cm-3,the propagation speed of the positive streamer remains unchanged throughout the discharge process,and is no longer affected by the negative streamer.The peak value of electric field decreases with the increase of pre-ionization level,and tends to be constant during streamer propagation.Based on the previous paper,this paper constructs the air discharge model under non-uniform electric field,complements with the previous paper,and forms a relatively complete set of air discharge simulation system under low temperature and sub atmospheric pressure,which provides a certain reference for future research.