Winckler J R
School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455, USA.
Proc Natl Acad Sci U S A. 1997 Sep 30;94(20):10512-9. doi: 10.1073/pnas.94.20.10512.
This paper deals with a luminous electric discharge that forms in the mesospheric region between thundercloud tops and the ionosphere at 90-km altitude. These cloud-ionosphere discharges (CIs), following visual reports dating back to the 19th century, were finally imaged by a low-light TV camera as part of the "SKYFLASH" program at the University of Minnesota in 1989. Many observations were made by various groups in the period 1993-1996. The characteristics of CIs are that they have a wide range of sizes from a few kilometers up to 50 km horizontally; they extend from 40 km to nearly 90 km vertically, with an intense region near 60-70 km and streamers extending down toward cloud tops; the CIs are partly or entirely composed of vertical luminous filaments of kilometer size. The predominate color is red. The TV images show that the CIs usually have a duration less than one TV field (16.7 ms), but higher-speed photometric measurements show that they last about 3 ms, and are delayed 3 ms after an initiating cloud-ground lightning stroke; 95% of these initiating strokes are found to be "positive"-i.e., carry positive charges from clouds to ground. The preference for positive initiating strokes is not understood. Theories of the formation of CIs are briefly reviewed.
本文探讨的是一种发光放电现象，它形成于雷暴云顶与90公里高空电离层之间的中间层区域。这些云 - 电离层放电（CI），可追溯到19世纪的目击报告，最终在1989年由明尼苏达大学“SKYFLASH”项目中的一台微光电视摄像机拍摄到了图像。1993年至1996年期间，多个团队进行了大量观测。CI的特征是：其水平尺寸范围很广，从几公里到50公里不等；垂直方向上从40公里延伸至近90公里，在60 - 70公里附近有一个密集区域，并有流光向下延伸至云顶；CI部分或全部由千米尺寸的垂直发光细丝组成。主要颜色为红色。电视图像显示，CI的持续时间通常小于一个电视场（16.7毫秒），但更高速度的光度测量表明它们持续约3毫秒，并且在起始的云 - 地闪电放电后延迟3毫秒；发现这些起始放电中有95%是“正向的”——即从云向地面携带正电荷。对正向起始放电的偏好尚不清楚。本文简要回顾了CI形成的理论。
