[meteorite-list] What makes a meteor glow?

[Mexicodoug]

A very kind list member messaged me about me about the sequence of 
events of energy transfer for an entering meteoroid. In step 4 I had 
written:

">4) Superheated air heats everything else it touches"

List member said:

"...I would expect that by far the lion's share of the heating of the 
meteoroid by the hot compressed air around it is mediated by radiation 
rather than by conduction (direct molecular contact)."

Reply:

I was very careless in some details I was arguing against by using the 
word "touch" which would imply collisions, conduction or convection, 
and you have a much improved wording that the radiation would be 
expected to be the main means of energy transfer in such high energy 
flux situations with so much power dissipation (happening so quickly in 
the plasma) not only for the meteoroid heating but also for the 
size/extent of the mass of affected superheated air. Since radiation 
travels faster than the incoming meteoroid, another thought is that 
would make the air in front have different properties before it is even 
shocked which could explain some of the peculiarities of why some 
meteorites don't fragment into nothing. No doubt this is covered in the 
literature somewhere, too?

...that said, in a plasma (=bulk reasonably ionized hot gas), who knows 
(not me) whether a lightning bolt doesn't essentially behave the same: 
takes (high electrical potential via discharge) energy instead of (high 
kinetic via compression) but the rest is the same: discharge superheats 
the air into a plasma (the "ions") and they relax emitting radiation 
which we see as lightning, and don't see the other energy as well from 
whistlers to X-rays - something of an interesting meteorological 
relationship.

A quick calculation would be to compare the kinetic energy of a 
"typical" bolide to the electrical energy released in a "typical" 
lightning bolt, or see at what convenient sizes they are equivalent. I 
wonder whose Daddy is bigger... bolide or bolt... Oh ... some other time


Kindest wishes,
Doug
...couldn't resist this thread...but probably should have ;-) Hope the 
rest is intelligible enough for the overall summary.


Subject: Re: What makes a meteor glow?


Hi Doug, 
 
At 22:24 29-06-10, you wrote: 
 
>4) Superheated air heats everything else it touches 
 
Though this is only an intuitive hunch not backed by knowledge of 
actual measurements, I would expect that by far the lion's share of the 
heating of the meteoroid by the hot compressed air around it is 
mediated by radiation rather than by conduction (direct molecular 
contact).