[meteorite-list] strewnfield size vs entry angle

From: Chris Peterson <clp_at_meteoritecentral.com>
Date: Sun Mar 5 12:02:13 2006
Message-ID: <069a01c64076$4f4fdb70$f551040a_at_bellatrix>

Hi Rob-

I think your methodology probably resulted in a biased formula. Falls
connected with witnessed fireballs are strongly associated with shallow
entry paths. Shallow paths produce multiple fragmentation events, or single
fragmentation events that extend over a long ground path. This results in a
strewn field that is more closely aligned with the entry path. As the path
becomes steeper, high altitude winds become more significant. For entry
angles greater than about 60? (from the vertical), winds are the dominant
factor in predicting the shape of the strewn field.

I need to use radiosonde data to estimate the potential strewn field for
most of the fireballs I track. Actually, the wind data is essential to
predict the _location_ of the field with respect to the fragmentation, and
usually important to predict the orientation and size of the strewn field.

Of course, my analysis is theoretical, not empirical. There simply isn't
enough data available to test the theory with any degree of statistical
significance. The number of falls that produced strewn fields with multiple
meteorites, and for which both atmospheric wind data and trajectory data are
available, can be counted on one hand.

Chris

*****************************************
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com


----- Original Message -----
From: "Rob McCafferty" <rob_mccafferty_at_yahoo.com>
To: <Meteorite-list_at_meteoritecentral.com>
Sent: Sunday, March 05, 2006 9:31 AM
Subject: Re: [meteorite-list] strewnfield size vs entry angle


I know a formula does exist for this because I did my
3rd year undergraduate project on exactly this and I
and another student wrote it.

It involved a lot of empirical evidence and
formulating a formula which fitted the very few
properly observed falls and seeing if it could be
extrapolated to other strewn fields.

The formula predicted very well the size distribution
for these and even allowed us to predict the incoming
angle for unobserved meteorite falls. The formula also
has a modification factor depending on whether it was
a stony or iron meteorite.

Obviously, I don't have a copy of this to hand it
having been 13 years ago and I don't have the
resources (nor the ability, which has waned sadly in
the intervening period) to re-derive it.

However, if you were to find an address or e-mail for
Professor David Hughes from Sheffield University, UK,
I dare say he sitll has it lying around in his office
as he was the Planetary Astronomer I studdied under.


Rob McCafferty
Received on Sun 05 Mar 2006 12:00:30 PM PST