Wkipedia has some wonderful pictures of this effect. They are called "shock diamonds" and occur when an military jet aircraft uses the afterburner. It's a shock wave set up in the reheated exhaust. When the military does a flyover they usually engage afterburner because it looks so cool and makes so much noise. You can see the striations if the sky is somewhat dark. I have seen them below dark overcast skies during our local airshow in Quonset, RI.
Google "afterburner jet waves" to see the pictures on the wikipedia link.
Bob at PC
-----Original Message-----
From: phys-l-bounces@carnot.physics.buffalo.edu [mailto:phys-l-bounces@carnot.physics.buffalo.edu] On Behalf Of David Strasburger-fac
Sent: Wednesday, April 07, 2010 3:39 PM
To: phys-l@carnot.physics.buffalo.edu
Subject: [Phys-l] standing waves in exhaust?
I saw a phenomenon Sunday night that I couldn't explain; I'd appreciate
ideas and thoughts from the list.
On Sunday evening the Red Sox played their home opener against the Yankees
in Fenway. The league, in its infinite wisdom, booked the game to be
televised nationally, so instead of being played at the traditional 1pm,
it was played at 8pm.
As a result, the flyover by a pair of figher jets from the Vermont Air
National Guard was all but invisible. As they passed overhead, the most
visible feature was a luminous pink/orange cone extending perhaps one
plane-length from the aft part of each jet. Inside each cone was clearly
visible a set of bright transverse lines (6 or 8, maybe?), evenly spaced
along the length of the cone.
Any suggestions as to what might cause this?
Is it as simple as:
jet ejects wicked hot air --> wicked hot air glows --> standing wave in
exhaust (created by?) means there exist local density highs in the plume
--> higher density glowing air looks brighter than lower density glowing
air