Corona discharge (d-060821-corona)
In gallery: Photos of the month (2006)
Related photos: Lightning
This photo shows natural coronal discharge, or St. Elmo's fire, off the top of an antenna mast. It was taken in the early evening of August 21, from the Langmuir Laboratory for Atmospheric Research in New Mexico (USA). The electric field at the time of this discharge was about +11 kV/m, under a dying thunderstorm.
Photographed with a Canon 300D digital camera on ISO 1600 with Nikon Nikkor 180mm/2.8 telephoto lens. (Special adapters are available to allow Nikon lenses to be mounted on Canon camera bodies.) Exposure time was 25 seconds. This is the only photo of a series of about 40 I took that shows the blue flame; all other frames only show two blue dots. Most likely the blue flame erupted shortly when a lightning flash occurred in the distance, shortly increasing the electric field. For a sense of scale, the rod with the coronal discharge is about 2.5 cm or 1" in diameter. The frame has been cropped to show the coronal discharge well. Langmuir Lab was designed and built for thunderstorm research, and is at an elevation of 3.2 km above sea level in the Magdalena Mountains. It is unique in its sort; specially constructed for safety during direct lightning strikes, it allowed me to stay safe while photographing this St. Elmo's fire from only a few meters distant.