Archive for category high-speed camera observations
A recent result published in the science journal Nature caught my attention. It described “needle-like” structures on positive leader channels that pulse in trail of the positive leader tip.
Two discussions on this recent publication can be found at the links below.
By Earle Williams and Joan Montanyà
By University of Groningen
The article itself is available at the link below, but must be purchased or obtained through an institution.
Back in 2008 and 2010, we captured upward positive leaders propagating from towers and noticed some pulsing structures that developed in trail of the positive leader tip. I called these “thorns” as they reminded me of thorns on a rose bush stem.
These “thorns” appeared to form at the location where the positive leader unsuccessfully attempted to branch as seen by the splitting of the corona brush shown in the video below.
These thorns started pulsing at regular intervals and in one case developed into a negative leader that propagated away from the positive leader channel as seen in the video below.
We published a brief description of our observations in a conference paper, but did not pursue investigating them further as this was outside of our research focus at the time. The recent findings published in Nature shed further insight into the how these “needles” (or “thorns”) develop and possibly relate to channel decay, current cutoff and redevelopment as well as new branch development; a challenging but important research topic at present. With the increased number of investigators utilizing high-speed video cameras, I suspect more video examples of this behavior will soon surface, and along with correlated electric field sensing instrumentation data, may allow for better understanding of this interesting behavior.
Over the past six years my research colleagues and I have filmed lightning using high-speed digital cameras. In total we have captured 776 naturally occurring lightning flashes with recording speeds as high as 100,000 images per second. 158 of these flashes were cloud flashes in which some of the lightning leaders propagated outside of the clouds. 372 of theses flashes were negative cloud-to-ground flashes (-CG) and 206 were positive cloud-to-ground flashes (+CG). 41 of the flashes were upward flashes originating from tall towers in Rapid City.
During this last summer, we pursued a storm into the Badlands of South Dakota. The Badlands are a beautiful area of erosion in the plains creating incredibly photogenic landscapes, and it is personally one of my favorite places to photograph lightning. On this particular day, I was filming from the Pinnacles Overlook looking east across a road. I filmed a number of flashes, but during one instance I not only captured a +CG flash, I also captured a rare wild tourist roaming the South Dakota plains. Because I film from a highly modified truck with cameras and gadgets sticking out of it, he was a bit curious by the appearance of my vehicle. However, he was clearly more interested in getting to the next viewpoint and quickly scurried off never to be seen again. Here is the video…
Below is a video on the creation of Lichtenberg figures. Interesting is the subsequent bright short discharges that continue to take place after the initial discharge. These seem similar in appearance to recoil leaders, which form on positive leaders branches that become cutoff from a main channel. Compare the two videos below.
YouTube video of Lichtenberg creation.
Upward lightning (upward positive leaders) from a tower filmed at 9,000 images per second.