1] The transient ELF (similar to50-5000 Hz) magnetic field radiated by lightning discharges across North America was continuously measured at Duke University during the summer of 2000. In total, 881 sprite-associated lightning discharges over 17 days were analyzed. We report in detail on 76 sprites for which we could reliably determine the lightning charge moment change from the ELF data at the time of sprite onset. The charge moment change for the initiation of a sprite is found to be as low as 120 C km. By folding together the charge moment distributions of sprite-producing lightning and all positive lightning, we find that the probability of sprite generation for lightning with >1000 C km charge moment change in <6 ms is >90%, while the sprite probability for lightning with <600 C km charge moment change in <6 ms is <10%. [References: 19
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机译：1] 2000年夏季，杜克大学连续测量了整个北美的雷电辐射所产生的瞬态ELF（类似于50-5000 Hz）磁场。总共分析了17天中881次与雪碧相关的雷电放电。我们详细报告了76个精灵，我们可以根据精灵开始时的ELF数据可靠地确定雷电的力矩变化。发现用于启动子画面的充电力矩变化低至120 C km。通过将产生子画面的闪电和所有正闪电的电荷矩分布放在一起，我们发现，在<6 ms内具有> 1000 C km的电荷矩变化的闪电，生成子画面的概率为> 90％，而对于闪电的子画面概率在<600 C km的情况下，充电力矩在<6 ms内的变化<10％。 [参考：19
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