This investigation is focused on groups of Narrow Bipolar Events (NBEs), defined as NBEs that occurred within 10 km horizontally and ±660 ms of a located, large-amplitude NBE from a dataset of positive NBEs that occurred in Mississippi thunderstorms. In two months only 15 groups were found, with a total of 31 positive and 4 negative NBEs. Each group had 2 to 5 NBEs; four groups had both positive and negative polarity NBEs. About half of the NBEs had typical values for range-normalized fast antenna (FA) electric field change magnitudes (4–15 V/m) and typical VHF powers (1000–45,000 W), but 17 NBEs had FA magnitudes 0.2–2.5 V/m, and 17 NBEs had VHF powers 30–900 W. Seven weak NBEs had FA magnitudes of 0.2–1.0 V/m and VHF powers of 30–100 W. These findings indicate that weak NBEs are more common than previously thought. None of the NBEs in groups initiated a lightning flash, and (with one possible exception) none of the later NBEs in a group were initiated by earlier NBEs in the group. The data of the NBE groups are consistent with the turbulence-extensive air shower (EAS)/relativistic runaway electron avalanche (RREA) mechanism, which states that each NBE occurs in a separate 1-km³ volume containing many small regions with electric field ≥3 MV/(m∙atm); an EAS/RREA passing through the 1-km³ volume initiates the positive streamers that comprise the NBE. Relative to thunderstorm radar reflectivity, 23 NBEs occurred in or above the reflectivity core, 10 NBEs occurred high in the storm anvil, and 2 NBEs occurred beside the storm core. We speculate that the occurrence of many of the NBE groups was associated with dynamically intense convection.

这项研究的重点是窄双极事件（NBE）组，它们定义为发生在密西西比州雷暴中的正NBE数据集中水平10 km内和某个大幅度NBE的±660 ms范围内的NBE。在两个月内，仅发现了15组，总共31阳性和4阴性NBE。每个小组有2至5个NBE；四组同时具有正极性和负极性NBE。大约一半的NBE具有典型值的范围归一化快速天线（FA）电场变化幅度（4–15 V / m）和典型的VHF功率（1000–45,000 W），但是17个NBE具有FA幅度0.2–2.5 V / m，17个NBE的VHF功率为30–900W。七个弱NBE的FA幅度为0.2–1.0 V / m，VHF功率为30–100W。这些发现表明，弱NBE比以前认为的更为普遍。群组中的所有NBE均未发起闪电，（一个可能的例外），群组中的较晚NBE均未由该群组中的较早NBE发起。NBE组的数据与湍流扩展风淋（EAS）/相对论失控电子雪崩（RREA）机理一致，该机理指出每个NBE发生在单独的1公里内³体积，包含许多电场≥3MV /（m∙atm）的小区域；穿过1 km ³体积的EAS / RREA启动构成NBE的正向拖缆。相对于雷暴雷达反射率，在反射率核心内或上方有23个NBE，在风暴砧高处有10个NBE，在风暴核心旁有2个NBE。我们推测许多NBE组的发生与动态强烈对流有关。