[meteorite-list] What makes a meteor glow?

From: Mexicodoug <mexicodoug_at_meteoritecentral.com>
Date: Tue, 29 Jun 2010 18:57:50 -0400
Message-ID: <8CCE5F5A22C8138-212C-1F94_at_webmail-d036.sysops.aol.com>

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).?
?
?
Received on Tue 29 Jun 2010 06:57:50 PM PDT