(Or to see one in motion, watch the end of the 'Die Hard' movie based at an airport ('Die Hard 2?). Right at the end our hero is out on the runway helping everyone to land lined up on the flames from the baddies' aircraft and an aircraft flies through a smoke plume. Perfect wingtip vortex results.)
There's a good example of a helicopter vortex (thru' smoke) in 'Apocalypse Now' too. (hehe....double
)