GEOMAGNETIC UNREST: 16 August 2013: A high-speed solar wind stream is buffeting Earth's magnetic field, and this is causing minor geomagnetic storms around the poles. High-latitude sky watchers should be alert for auroras.
speed: 745.3 km/sec
density: 1.0 protons/cm3
Sunspot number: 129
First documented in 1989 by scientists from the University of Minnesota who photographed strange flashes coming out of the tops of thunderstorms, sprites remain a mystery today. Neither their basic physics nor their effect on the surrounding atmosphere is well understood. "Do sprites have a large scale impact on the middle atmosphere?" asks Ahrns. "Sprites clearly represent some kind of transfer of energy, but is it on a scale that has a significant effect on the weather and climate? We can't answer that without studying them."
The ephemeral nature of sprites (they typically last no more than a few milliseconds) makes them tricky to study. Researchers on the NCAR Gulfstream capture sprites using Phantom cameras running at 10,000 frames per second. "One of the Phantoms has a diffraction grating in front of it to capture high speed spectra, which I don't think has ever been done before," notes Ahrns.
The prettiest pictures, though, come from Arhns' own camera, a dSLR that he mounts in the window of the airplane to capture "beauty shots." The image above is an example.