Ionization Effect of Atmosphere by Prompt $\gamma$ Rays From High-Altitude Nuclear Explosions

The ionization processes and temporal evolutions of atmosphere ionized by prompt γ rays from high-altitude nuclear explosions are studied by numerical simulations. With the increasing of the burst point, the peak energy density of the Compton electrons decreases, but the corresponding altitude of the peak rises, which is 30 km directly below the burst point, and 40 km-50 km below the burst height 1000 km from the burst point following Earth´s surface curvature. It is shown that the prompt γ rays have significant ionization effects on the atmosphere from the burst point to several kilometers from the burst point, and the affected area increases with the rising of the burst point. By the secondary ionization, the Compton electrons produce many more low-energy electrons whose lifetime increases with the rising of the altitude.