Global distribution and properties of continuing current in lightning

Continuing current is a process in lightning in which the current in a conducting channel can flow for much longer than in a typical lightning discharge. The phenomenon can be characterized by the continuous optical emission that accompanies the current flow. Using the Lightning Imaging Sensor ( LIS), lightning with continuing current is identified on a global scale. Lightning that contains optical emission over at least five consecutive LIS frames, roughly 7-9 ms, are classified as continuing current flashes. This differs from typical lightning discharges that produce optical emission for one or two consecutive frames. Of the flashes detected by LIS, 11.2% contain continuing current. These flashes optically radiate over a larger footprint and have a longer duration than ones that do not. The spatial distribution of these flashes indicates that regions of high lightning activity may not be correlated with a high likelihood of continuing current flashes. Further, oceanic and winter lightning are shown to have a higher proportion of continuing current flashes. Finally, 25-40% of flashes identified by LIS to have continuing current have only an intracloud pulse detected by the National Lightning Detection Network (NLDN), with no cloud-to-ground strokes detected.