Chelyabinsk Meteor Shockwave 2/15/2013

mfb

Many, fast particles flying through the atmosphere heat a lot of air. And a lot of hot air in some region is a fireball.

A significant increase in air drag due to fragmentation.
Hot air radiates, just as it does in a fire. Blackbody radiation, plus some parts due to internal transition in molecules.

Zorwell

Is fragmentation alone enough to cause the rapid transition from a burning meteor streaking through the sky leaving something like a contrail to the rapid increase in size and brightness that we saw? The amount of light produced and the size of the "explosion" (variously estimated from 0.1 to 300 kilotons) suggests, at least to me, something more dramatic, such as abrupt vaporization and combustion. But that's just my guess.

Paulibus

A fluid like water feels hard to someone jumping off the Golden Gate bridge, so they say, and I believe "them", although I've never tried this folly myself! If a poor little asteroid doing nothing but just falling freely is swatted by a great big planet and made to accelerate to relative rest at several tens of "gees", even the planetary atmosphere must seem much harder to it than the sea does to a jumper. Think tornadoes blowing at speeds of km/sec! The asteroid's presumed non-aerodynamic shape and heterogeneous make-up will then make the forces that accelerate it generate internal stresses that are both inhomogeneous and extreme, which are likely to cause very sudden fracture and a (small b's) big bang. Think of throwing a large diamond into a jet intake. Not that you would dream of actually doing this!

Then glappkaeft's scenario (post #7) takes over.

mfb

The energy of any chemical reactions is small compared to the kinetic energy of the asteroid. Smaller parts have a higher drag to mass ratio, so they lose their kinetic energy quicker than the big part. If the material is not very stable on a large scale, I could imagine a quick fragmentation of those fragments as well, further increasing air drag.

glappkaeft

A useful rule-of-thumb is that an object travelling at 3 km/s has the same kinetic energy as a similar mass of TNT has chemical energy. Now if the meteor was travelling at 15-18 km/s the meteors kinetic energy would be equivilent of 25-36 times its mass in TNT.