中高层大气瞬态发光事件(TLEs)是发生于活跃雷暴上空平流层和中间层的一类快速大气放电现象。根据光辐射的形态特征和发生位置的不同,可将已发现的TLEs归纳为4类:由电离层快速向下发展的Red Sprites(又称红色精灵,红闪);由雷暴云顶部向上发展的Blue Jets(又称蓝色喷流,蓝激流);由闪电激发的低电离层区域的圆环状放电ELVEs(Emissions of Light and VLF per-turbation due to EMP Sources,又称光辐射和EMP源引起的甚低频扰动)和由云顶向电离层快速向上发展的Gigantic Jets(又称巨大喷流)。对已有的TLEs现象学和形态特征的观测事实以及物理机制和理论研究等进行了回顾,讨论了TLEs对平流层和中间层大气以及电离层的可能影响,并提出了目前在TLEs理论方面尚未解决的问题,指出了进一步观测和理论研究的必要性。
Red sprites, different from lightning flashes occurring in the troposphere, are large and brief dis-charges which appear in the altitude range from about 40 to 90 km above large thunderstorms and are usually caused by cloud-to-ground lightning discharges (CGs). A total of 17 sprites over two thunder-storms were first observed during the summer of 2007. One of the sprites occurred on July 28 above a thunderstorm in Guan County and the center of the storm was about 272 km from the observation site. The other sprites were recorded at the late night of August 1 and in the early morning of August 2, and the storm center was about 315 km away. All of the observed sprites occurred in cluster, and their appearances were very different, including 'columniform sprites', 'columniform sprites' with angel-like wings, 'carrot sprites', 'dancing sprites', etc. The duration of the sprites varied from a minimum of 40 ms to a maximum of 160 ms with a geometric mean (GM) of 61 ms. The time delay between parental positive cloud-to-ground lightning flashes (+CGs) and the associated sprites varied from 3.4 to 11.8 ms with a GM of 7.1 ms. The ratio of the number of +CGs to the total number of CGs during the time period with sprites was 7 times larger than that when no sprites occurred. Sprites did not appear fre-quently at the time when the convective activity is strong but when the thunderstorm starts to become weak.
YANG JingQIE XiuShuZHANG GuangShuZHAO YangZHANG Tong
