Red sprites (d-070906-224)

In gallery: Photos of the month (2007)
Related photos: Lightning

During a split second a ghostly group of red sprites appears over a mesoscale convective system over the Texas Panhandle (USA), itself well beyond the horizon and invisible. Red sprites are middle-atmospheric electric discharges which may be triggered when the electric field between extensive thunderstorm tops and the ionosphere suddenly changes, as happens when a powerful cloud-to-ground lightning flash occurs.

The sprites occurred a good 300 miles east of the Langmuir Laboratory for Atmospheric Research in New Mexico, where I was stationed for lightning research. The lab is at an elevation of 3.1 km above sea level and offers an unprecedented view of such elusive discharges. The photograph was taken with an infrared-modified Canon 300D digital camera set at 1600 ISO, using a Nikon 50mm f/2 lens with adapter. The exposure time was on the order of 10 seconds. The photo only shows the brightest central parts of the sprites; the sprites in their entirety filled most of the frame but the weaker branches did not register.