“闪晕”的电场结构和光辐射的时变模拟

Time-Dependent Simulation of Electrical Field Configuration and Optical Emission of Sprite Halo

用时变的2-D准静电场模型,研究了由雷暴放电产生的静电场在中间层-低电离层的空间结构、时延、持续时间、向下传播的速度以及静电场引起的大气电离和光辐射。研究表明,由静电场引起的氮分子第一个正波段光辐射的时空特征与观测到的“闪晕”时空特征基本一致。

Using the two-dimensional, time-dependent quasi-electrostatic field （QEF） code, the configuration, time delay, duration and descending motion speed of quasi-static electric field caused by thunderstorm discharge was investigated, and the effects of atmospheric ionization and optical emission in mesosphere and low ionosphere caused by this QEF was also studied. Research show： the sprite halo initiates at 85 km and with a pancake-like shape, then the regions of breakdown and optical emission move downward at speed of 1.5 × 10^7m·s^-1, the regions of breakdown and optical emission gradually become an upward concave shape. Sprite halo lasts about 5.5 ms with a height range of 64-87km, and with a horizontal scale of 80 km. Moreover, simulation results indicate that appearance time of the maximum of optical emission occurs at the time of t = 2.1 ms, which is delayed to thunderstorm discharge. And the QEF does not monotonously decrease with the altitude increasing, it has complicated structure at symmetrical axes. In addition to, the QEF cause atmosphere breakdown ionization and lead to electron density increases （ionization coefficient 〉 attachment coefficeint） or decreases （attachment coefficient 〉 ionization coefficient）. At altitude of 70 km, the increased electron density of Ne = 2.178 × l0^8 m^-3 is much bigger than the fair weather electron density of Ne = 6.329 × 10^5 m^-3.