The optical and VHF instrumentation on the fast on-orbit recording of transient events (FORTE) satellite is used to document the combined phenomenology evolution of a lightning “megaflash”—Mesoscale lightning that propagates laterally over exceptional distances. We identify a FORTE flash whose maximum extent was 82 km and inferred length over multiple distinct branches exceeded 100 km. This flash lasted 1.2 s and produced 250 optical and 591 radio frequency events. We find that the channel development mapped by FORTE's pixelated lightning imager (LLS) occurred at a typical speed of 2.6 × 10⁵ m s⁻¹ and was accompanied by sustained periods of VHF emission that could individually exceed 100 ms in duration. The impulsive IC events generated by the flash indicate that this development occurred at altitudes between 3 and 8 km. Four +CG strokes were identified in the VHF waveform data that are responsible for two of the three highly radiant LLS groups (two of the +CGs were not as optically bright as the others). These strokes occurred at different locations throughout the flash footprint with the most distant strokes separated by approximately 50 km. These space-based observations match previous observations of megaflashes as well as ground-based measurements of negative leader development during “spider” lightning, suggesting that FORTE is sensing the same phenomena.

中文翻译：

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FORTE 卫星对闪电巨闪的光学和射频组合测量

瞬态事件快速在轨记录 (FORTE) 卫星上的光学和 VHF 仪器用于记录闪电“超级闪电”的组合现象学演变——中尺度闪电在异常距离上横向传播。我们确定了一个 FORTE 闪光，其最大范围为 82 公里，多个不同分支的推断长度超过 100 公里。这次闪光持续了 1.2 秒，产生了 250 个光学事件和 591 个无线电频率事件。我们发现由 FORTE 的像素化闪电成像仪 (LLS) 映射的通道发展以 2.6 × 10 ⁵  m s ^-1的典型速度发生并伴随着持续时间可能超过 100 毫秒的 VHF 发射持续时间。闪光产生的脉冲 IC 事件表明这种发展发生在 3 至 8 公里的高度。在 VHF 波形数据中确定了四个 +CG 中风，它们负责三个高辐射 LLS 组中的两个（其中两个 +CG 的光学亮度不如其他）。这些中风发生在整个闪光足迹的不同位置，最远的中风相距约 50 公里。这些天基观测与先前对巨型闪光的观测以及“蜘蛛”闪电期间负先导发展的地面测量相匹配，表明 FORTE 正在感知相同的现象。