This study describes results from video observations of five intracloud flashes located ≤ 20 km from the camera and recorded with 6.1 µs exposure time and 6.66 µs frame intervals. Video data are supported with electric field change (E-change) and VHF measurements, with emphasis on the flash initiating event (IE) and initial breakdown (IB) stage. In four of the five flashes, the IE is accompanied by weak luminosity, ≤ 5% above background, lasting for 300–500 µs. Two of these four IEs were positive Narrow Bipolar Events (NBEs) with VHF powers of 43 and 990 W; these are the first (known) data showing visible light detected with a positive NBE. Two other IEs with weak luminosity had powers of 0.5 and 1 W, and the IE with no detected luminosity had a VHF power of 3 W. A typical IB cluster consists of several narrow pulses and one classic pulse in E-change data (along with many VHF pulses), and each example flash has 2–10 IB clusters in the first 5–50 ms. The luminosity of IB clusters was substantially greater than IE luminosity, ranging from 10 to 40% above background in four examples, while for one flash with 10 IB clusters, the luminosity range was 35–360% above background (average 190%). Luminosity durations of IB clusters were 520–1750 µs with average 1210 µs. For both IEs and IB clusters, increases in the detected luminosity were closely timed with substantial VHF emissions and decreased when VHF emissions weakened.

这项研究描述了从距离相机≤20 km的五次云内闪光灯的视频观察结果，并记录了6.1 µs曝光时间和6.66 µs帧间隔。电场变化（E-change）和VHF测量支持视频数据，重点是闪光引发事件（IE）和初始击穿（IB）阶段。在五次闪烁中的四次中，IE伴随着弱的发光度，比背景光低5％，持续300-500 µs。这四个IE中的两个是具有43和990 W VHF功率的正窄双极事件（NBE）。这些是显示已知NBE阳性的可见光的第一个（已知）数据。其他两个发光度较弱的IE的功率分别为0.5和1 W，没有检测到发光度的IE的VHF功率为3W。一个典型的IB群集由E转换数据中的几个窄脉冲和一个经典脉冲（以及许多VHF脉冲）组成，每个示例闪光灯在前5–50 ms内具有2–10个IB群集。IB群集的发光度显着大于IE的发光度，在四个示例中，其发光度比背景高出10％至40％，而对于具有10个IB群集的闪光灯，其发光度范围比背景高出35–360％（平均190％）。IB群集的发光持续时间为520-1750 µs，平均为1210 µs。对于IE和IB群集，检测到的光度的增加与大量VHF排放密切相关，而当VHF排放减弱时则降低。在四个示例中，其亮度比背景高10％至40％，而对于具有10个IB群集的闪光灯，其发光度范围比背景高35–360％（平均190％）。IB群集的发光持续时间为520-1750 µs，平均为1210 µs。对于IE和IB群集，检测到的光度的增加与大量VHF排放密切相关，而当VHF排放减弱时则降低。在四个示例中，其亮度比背景高10％至40％，而对于具有10个IB群集的闪光灯，其发光度范围比背景高35–360％（平均190％）。IB群集的发光持续时间为520-1750 µs，平均为1210 µs。对于IE和IB群集，检测到的光度的增加与大量VHF排放密切相关，而当VHF排放减弱时则降低。