(meteorobs) Question about fireball brightness

[GeoZay at aol.com]

>>This question is seeking a sort of rule of thumb.  I  was
looking north, and the sky lit up behind me and I turned
around fast  enough to see the last half of the fireball,
which was bright green and  fragmented into a few pieces.
The question is, how much brighter than the  local limiting
magnitude does a fireball have to be to attract  your
attention from behind?  That night where I was (a  suburban
location where on the very best moonless nights the Milky
Way  is faintly visible), the LM was probably about +4.5.
My friend, who was not  wearing his eyeglasses, estimated
it was -6, but I thought it had to be  brighter than that
to attract my attention from behind.  So, is there  a rule
of thumb about a fireball's magnitude in this type of
situation  -- the fireball being bright enough (not to
mention lasting long enough) to  induce you to turn around
180 degrees to see it?<<
 
I guess you'd have to consider what makes a person "sense" something is  
going on behind them. Most likely they see a combination of lit up objects and  
moving shadows that makes them want to turn around for a better look. The  
question comes to mind then, "How bright does a meteor must be to light up  objects 
and produce noticeable shadows? " I believe a meteor in the neighborhood  of 
-4 will produce shadows. So...I'd say your fireball had at least  a minimum 
magnitude of -4. I believe most people have a tendency to  overestimate a 
meteors magnitude...particularly the more brighter ones. If  your friend estimated a 
-6, I would think then this to be reasonable. 
George Zay