[meteorite-list] Meteoroid/Asteroid Electro-Magnetic Disruption and Charge Properties?

From: Carl Agee <agee_at_meteoritecentral.com>
Date: Wed, 27 Feb 2013 10:42:36 -0700
Message-ID: <CADYrzho04xOocdt9rNffE-8PaEsx+DRgatTh=GatCvq0CJBJCw_at_mail.gmail.com>

Hi Chris,

Do you have any references you could point me to for how break-up
scales with size-mass-physical properties etc. of meteoroids. I am
interested in knowing the "sweet-spot" for yielding meteorites on the
ground. In other words, when is a meteoroid too small or too big to
produce significant large pieces of surviving material? It seems like
Chelyabinsk is outside the sweet spot as it apparently produced mostly
fragments even though it had large mass. On the other hand much bigger
masses may also survive. Is it bimodal?

Thanks,

Carl Agee

-- 
Carl B. Agee
Director and Curator, Institute of Meteoritics
Professor, Earth and Planetary Sciences
MSC03 2050
University of New Mexico
Albuquerque NM 87131-1126
Tel: (505) 750-7172
Fax: (505) 277-3577
Email: agee at unm.edu
http://meteorite.unm.edu/people/carl_agee/
On Wed, Feb 27, 2013 at 9:21 AM, Chris Peterson <clp at alumni.caltech.edu> wrote:
> A body larger than about a centimeter transfers its kinetic energy to other
> forms primarily by compressing the air in front of it as it descends into
> the atmosphere. The pressure involved is typically very large- tens or
> hundreds of megapascals for meter-class bodies. Once this ram pressure
> exceeds the material strength of the body, it breaks apart (presumably along
> existing fault lines, so the material properties of the body are important-
> and generally unknown).
>
> Before the breakup, the heat created by compressing air is melting the
> surface of the meteoroid, resulting in ablation. This ablation is
> responsible for some of the light we see (along with atmospheric ionization
> from the same heat source), but is not particularly disruptive to the
> meteoroid. Only the outer surface is affected. Ablation is a very efficient
> way of removing energy (which is why spacecraft heat shields prior to the
> shuttles were ablative). When the meteoroid fragments at hypersonic speeds,
> however, additional surface area is instantly exposed, resulting in a rapid
> heating of the surrounding air (which is just a fancy way of saying
> "explosion"). If a body breaks into just a few pieces, as is common, we may
> see a central or terminal brightening. If it completely shatters into
> thousands of pieces (as seems likely with Chelyabinsk) the energy from the
> suddenly heated air is immense- an efficient conversion of kinetic energy to
> thermal energy. The expanding hot air can produce an impressive sonic wave,
> and probably further disrupts the meteoroid itself.
>
> I don't that there are any electrical forces of a significant size to affect
> the structure or motion of the meteoroid, although atmospheric electrical
> effects probably occur (e.g. electrophonics).
>
> Chris
>
> *******************************
> Chris L Peterson
> Cloudbait Observatory
> http://www.cloudbait.com
>
> On 2/26/2013 11:59 PM, drtanuki wrote:
>>
>> Dear List,
>> If there is anyone willing to discuss the how and why meteoroids/asteroids
>> "detonate" please explain for the list and myself.  I am interested learning
>> more about the electrical/mechanical/physical forces that these bodies
>> undergo as they reach the earth such as in the latest Russian event. Thank
>> you.
>> Dirk Ross...Tokyo
>
>
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Received on Wed 27 Feb 2013 12:42:36 PM PST