Blue Jet Observed Over Central Michigan
May 05, 2012
Photographer: Mark Grubaugh
Summary Author: Mark Grubaugh
The photo above shows a seldom seen blue jet emanating from a distant thunderhead as observed over Elsie, Michigan. It's the faint bluish jet or streak of light just above the black walnut tree (Juglans nigra) on the right side of the barn. I was photographing this lightning storm, which was probably about 30 mi (48 km) to the north of my home, in the early summer of 2008. At the time, I didn't even realize what I had captured until going through my lightning archives a few months back. I recently contacted Dr. Walter Lyons at FMA Research who confirmed that this was indeed a rare ground capture of a blue jet -- most observations are made from aircraft.
Blue jets are a type of high altitude lightning phenomenon, distinct from red sprites. These jets are optical ejections from the top of the electrically active core regions of thunderstorms -- quite often severe storms. After emerging from the top of the storm, they're observed to propagate upward in narrow cones of about 15 degrees and at velocities of roughly 100 km/s (Mach 300). They typically disappear from view at heights between about 65-80 mi (40-50 km).
Photo taken at 11:41:01 p.m. on June 15, 2008. I was shooting from a cornfield with a gibbous Moon to my back. The camera was pointed north and slightly east. Cassiopeia lies above the black walnuts and to the left of the blue jet.
Photo details: Camera: Canon EOS DIGITAL REBEL XTi; Lens: Tamron 28.0-80.0mm; Focal Length: 41/1mm; F Number: f/10; Exposure Time: 60/1; ISO Speed Ratings: 800; Metering Mode: Average; Exposure Program: Manual; White Balance: Auto white balance; Flash: Flash did not fire, compulsory flash mode; Software: Adobe Photoshop Elements 9.0 Windows.