Recently, a new lightning phenomena, termed needles, has been observed in both VHF and in optical along positive lightning leaders. They appear as small (<100 m) leader branches that undergo dielectric breakdown at regular intervals (called twinkles). Providing a coherent and consistent explanation for this phenomenon is challenging as each twinkle is a form of negative breakdown that propagates away from the positive leader. In this study, we provide detailed observations of needles in VHF, observed during two lightning flashes. We show distributions of different needle properties, including twinkle propagation speeds, time between twinkles, and needle lengths, among others. We show a return stroke and multiple recoil leaders that quench needle activity. We also show that nearby needle activity does not seem to correlate together, and that needle twinkling can slow down by 10%–30% per twinkle. We conclude by presenting possibilities for how the positive leader could induce negative propagation away from the positive channel, and we argue that twinkles can propagate like a stepped leader or like a recoil leader depending on the temperature of the needle, which implies that needle twinkles can probably propagate without emitting VHF.

中文翻译：

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针的传播和闪烁特性

近来，在VHF和沿正向雷电引导的光学装置中都观察到了一种新的闪电现象，称为“针”。它们显示为小的（<100 m）引导分支，这些分支会定期发生介电击穿（称为“闪烁”）。为每个现象提供一个连贯一致的解释是具有挑战性的，因为每个闪烁都是从正向领导者传播的负向分解的一种形式。在这项研究中，我们提供了在两次闪电中观察到的VHF针的详细观察。我们显示了不同针头特性的分布，包括闪光传播速度，闪光之间的时间以及针长等。我们展示了一个回程和多个后座引导器，这些针头可以终止针头的活动。我们还表明附近的针头活动似乎并没有相互关联，而且每转一圈，针的闪烁速度会降低10％–30％。最后，我们提出了一些可能性，即正向引导可能如何诱发正向通道以外的负向传播，并且我们认为，闪点可以像步进引导者或反冲引导者一样传播，具体取决于针的温度，这意味着针的闪烁可以可能会传播而不发射VHF。