Figure 2
From: Optical observation of needles in upward lightning flashes
Needles along a positive branch, (a) Nine needles in a time integrated image of an upward flash. A tenth needle was also observed but not shown here because it was too dim. (b) The upward leader right before the formation of needle number 3. It shows a normal corona brush (on the right branch), and the split corona brush (on the left branch) that generated needle number 3 on the left image (from Case 1—exposure time of 111 µs).
