It looks like there's a mini thunderstorm going on in this cockpit, with crackles of electricity spraying continuously across the windshield.
St. Elmo's Fire, a shocking weather phenomenon given the poetic shout-out by Shakespeare, is known for creeping up the masts of ships and making them glow like Christmas trees. Thus its holy name, which is a reference to the patron saint of seafarers, Erasmus of Formiae. If you're ever sailing and see the unworldly glow of St. Elmo forming, get inside the cabin; lightning could strike the boat within 5 minutes.
But St. Elmo's Fire, caused by a powerful buildup of static electricity, can pop up in other forms of transportation – notably airplanes. This happens in a couple of different ways: A jet might collect a negative charge by flying through floating particles like rain or snow, or simply borrow one from a nearby thunderstorm. As the aircraft works to shed the mounting static charge, glimmering plasma coats its wingtips and crackles across the cockpit windshield, making it appear like a miniature thunderstorm is occurring inches from a pilot's face. (See below for videos.)
These electrical takeovers, known in the aviation community as "precipitation static," look alarming but are mostly harmless to pilots who know their business. St. Elmo's fire can screw with radio communication, but it's also fun to play with. Here's Captain Meryl Getline describing one encounter with Elmo in USA Today:
When St. Elmo made an appearance, we could sometimes reach out to the front windshield and create what looked like miniature lightning bolts between the tips of our fingers and the windshields and then "play" with them—moving them around by manipulating our fingers (kind of like those spark-filled globes you see at children's science museums). The sensation was something like what you feel when an extremity has gone to sleep and tingles as it wakes up again. It didn't feel like a shock, but just kind of tickled.
So what's it look like? Read on....
This plane exploded into an airborne disco party when it accrued St. Elmo's Fire by passing through ice crystals above 37,000 feet. Says the person who posted the video: "This lasted off and on for a few minutes at a time for about an hour. We had very poor - virtually no - radio communications with [Air Traffic Control] in moderate precipitation static for over an hour":
Here's an Elmo outbreak on the nose cone of a plane flying from Bangkok to Vienna. In case you're wondering why a pilot would direct a jet through a thunderstorm, protocol dictates that going directly through is better than turning around because the aircraft's time inside the storm is thus minimized:
How about St. Elmo's Fire seen in night vision? The aircraft is a military-grade KC-10 Extender:
And check out this video from a pilot trying to avoid flying over Iran by traveling through an Iraqi thunderstorm. Nature really throws everything at the guy, who describes the night as the "scariest moment I've ever had flying":